/ohm/ - electronics general

What kind of crystal oscillator circuit would you recommend for a 4MHz crystal? How about a 32.768kHz? I'm looking for a square-wave output, but I could always use a comparator on a dirty sine wave instead; I'll probably have to use a buffer on it either way. The duty cycle doesn't matter as long as it's between 85% and 15%. The only tutorials I could find don't specify the output waveform.

File: HDMI-TERM_5.jpg (134KB, 800x1200px) Image search: [Google]

134KB, 800x1200px

Is it possible to solder and hdmi connector directly to the i/o pins of a fpga or I will need proper termination?

>>1191618
Depends. Some fpga have on chip termination settings

File: screen.png (289KB, 1411x980px) Image search: [Google]

289KB, 1411x980px

>>1191621
uhm, according the datasheet my device should support it, but on the pin planner I can only find an "output termination" option.

>>1191633
Don't know where to find the settings in quartus, but did find the relevant hardware docs https://www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/hb/cyclone-iv/cyiv-52001.pdf, looks like you shouldn't need external termination but may need ac coupling caps.

File: 1490718985386.png (23KB, 840x751px) Image search: [Google]

23KB, 840x751px

>>1191552
this circuit works any time you have a spare inverting gate. the capacitors depend on the crystal and the low value resistor depends on the frequency. i don't know that it's strictly necessary but allegedly it keeps sharp transients from damaging the crystal and i assume it prevents the parallel capacitance from doing anything funny to the waveform with the high frequency content of a sharp square wave. the high value resistor seems useless to me but i guess it adds some dc termination to the input side in a powered down state.

Any basic soldering hints you can give to a newfriend?

>>1191671
hold the iron on the joint for 2-5seconds so that it's touching both of the ends, then start feeding the solder into the contact point.

>>1191671
Keep the tip very clean and shiny. Parts should be very clean also.
When joining parts, tin both parts first.
A hotter iron can put less heat into a sensitive part if you're quick.

Easy way to join wires:
-tin both wires
-cut the tinned wires short, 1/4" or less
-hold the wires together using both hands while holding your hands together.
-touch to stationary tip until solder melts.

File: 32k_osc.png (8KB, 488x379px) Image search: [Google]

8KB, 488x379px

>>1191666
The reason for the high resistor values is that typical 32.768 kHz crystals are specified for a maximum drive level of 1 µW. Less is better and lowers the drift. Details at:
http://www.acierta-it.com/jas/v3.0/CD%20CON%20TODO/DCRABBIT_9.21/Docs/refs/TN235/TN235.htm

>>1191694
ah i was looking at MHz crystals for the values

>>1191656
ok thanks.
Another problem is that the lack of TMDS support make it impossible to use the hdmi port as input (but honestly I don't understand why it's not a problem for driving a monitor), do you think I could use some HDMI->LVDS adapter in that case?

File: 20170611_124430.jpg (130KB, 1600x900px) Image search: [Google]

130KB, 1600x900px

Quick question: Does anyone know what these are?

A friend of a friend found these inside a wall at home, brought them to a hardware store and somebody told her that they look like spy devices. She feels very distressed by this and seems to have a predisposition to paranoid thinking. I don't know what they are, but I'm doubtful that they are spy devices. I was just hoping maybe someone here could identify them.

Sorry for the non-DIYish post.

>>1191741
looks like some wire connectors

>>1191741
can you remove the plastic cover from one of those?

>>1191741
crimp connectors

http://www.allelectronics.com/item/urc/3-wire-telecom-butt-splice-ur/1.html

>>1191741
Telephone wire crimps
My house had a bunch in it too, before I ripped all the old telephone wiring out

>>1191747
>>1191745
>>1191744
>>1191743
Thanks a lot for the help, guys! I hope that will help ease her anxieties a bit.

>>1191666
Would an inverting buffer (74LS04) work instead? I'm not sure if it has a sharp on/off like an inverter does or if it acts like a voltage follower.

>>1191510
Ty OP, this is super helpful for me. I've been looking for better learning materials.

>>1191985
It's always here.

File: clarity-aloft-classic.jpg (14KB, 579x457px) Image search: [Google]

14KB, 579x457px

I want to cobble together a cheap imitation of the Clarity Aloft aviation headset (pic related).

I've got a good set of noise-blocking earbuds that I can use (I'll add some resistance to bring up the impedance) and the frame and wiring will be no problem.

My problem is finding an appropriate microphone (high impedance, amplified, noise cancelling) for less than full aviation prices (>$60 per unit).

Does anyone know of an appropriate microphone that runs less than $50?

If I use PWM with a DC motor and I want to measure the current with a digital ammeter, do I have to set it to DC current or AC current? It says "True RMS AC" on the ammeter

>>1191510
Anyone here try to use a homemade battery to power small electronic devices? If so, what did you use? what were the volts and amps

Was looking at making a homemade usb battery bank. Got a rough gist of what I need but I just want someone to quickly go over it and confirm what I have is correct:

10*18650 lipo batteries will be connected in parallel. This would then be connected to 3*TP4056 (5v 1a) chargers (mostly going to be capping out at 2a but in the event I need to charge it quickly I can connect to a 3a supply).

Batteries will also be connected to a CN6009 to output to a usb type a connector. CN6009 will be configured to output 5v.

This should be fine right?

>>1192062
Also will I run the risk of overcharging/undercharging the circuit? I will have a voltmeter connected to the batteries to check the voltage across the bank and I won't use it when it is too low.

As for overcharging the TP4056s should take care of that correct?

>>1192057
Some guy a while back as building his own Aluminium-air cells inside drinking straws, they looked pretty cool. The current was tiny though.

File: Screen Shot 2017-06-12 at 7.38.55 PM.png (18KB, 474x398px) Image search: [Google]

18KB, 474x398px

Just bought all 10 shift registers, plus two hex inverting buffers. This frequency divider might be my first project that requires two breadboards. I'd be trying out the crystal now if the shop hadn't kicked me out for staying past closing time. Surplustronics NZ sure has good prices, but their component shelves are just in "general alphanumeric order", so it took 3/4 of an hour to find what I was looking for. They also sell slide potentiometers.

I happened to have a trimmer cap on me, so I picked this circuit. Also because it's the only one that actually specifies component values and works for a 32.768kHz crystal, so it had better be a good one. Is a BC548 a decent replacement NPN for the pictured one? It has much higher hFE at low current, does this matter?

File: 2N3904-BC548-pinout.jpg (14KB, 320x352px) Image search: [Google]

14KB, 320x352px

>>1192146
>BC548 a decent replacement?
Yes, especially the B and C versions because of the low base current (3M3 resistor). Note the mirrored pinout.

>>1192174
I definitely noticed the mirrored pinout. Makes you wonder why they don't standardise them, or make transistors with nice little diagrams on them. I know it's too much to ask for SMD chips, but surely TO-92s having a "B","C", and "E" written on them wouldn't be too difficult, maybe an arrow to indicate polarity. I'm actually surprised that nobody makes these to get a foothold in the hobby market, instead everything's going the way of SMD.

Another thought to improve prototyping: Is there some way of loading a spice file (or other circuit simulation file) onto a microcontroller and having it behave as the components modelled in the spice file would? It shouldn't be too hard to implement in a bog-standard ATMega, provided you've got the software in place. If you did it well enough you could even model voltage sources inside the simulation to be potentially higher than the microcontroller's supply voltage, provided it doesn't need to output anything higher than the supply voltage. Maybe it would be easier to implement on a Raspberry Pi.

>>1192205
>"B","C", and "E" written on them wouldn't be too difficult
At least Motorola made such transistors. Dunno if ON Semi still prints EBC on their TO-92 packages.
>Makes you wonder why they don't standardise them
You could use TO-18 or TO-5/TO-39 transistors. They have standard pinout.
>I know it's too much to ask for SMD chips,
Practically all the SOT-23 and related transistors have identical pinout.
> It shouldn't be too hard to implement in a bog-standard ATMega
There's at least one at least somewhat real-time SPICE variant (livespice) for PC, but I don't know how well it works. That said, even if SPICE would fit in < 8kB of RAM, it still uses floating point math which isn't exactly the strong point of AVR.

>>1192052
You want DC

File: 19700103_185313[1].jpg (651KB, 1600x1200px) Image search: [Google]

651KB, 1600x1200px

What is this called?

>>1192414

version 21 of granddad's electro-masturbation device.

if you want to give grandad an actual working device, check https://en.wikipedia.org/wiki/Orgasmatron

>>1192419
That doesn't really help. I found it in my shed, I know these things from school but forgot the name. But from your comment I guess it is neither useful nor worth anything.

>>1192414
more pics

File: 19700103_213654[1].jpg (550KB, 1600x1200px) Image search: [Google]

550KB, 1600x1200px

>>1192448
Sorry for the low quality of my shitty tablet camera, that's all I got.

File: 19700103_213813[1].jpg (635KB, 1600x1200px) Image search: [Google]

635KB, 1600x1200px

>>1192489

>>1192489
absolute fucking shot in the dark but i would guess its some kind of bench power supply.
holes at the top to select various transformer tappings gives voltages, plug the flying leads to select the voltage you want, the holes at the bottom gives you 2A of AC at the right and the little diode and +/- is 1A of DC on the left.

could be for anything, homemade for tinkering, maybe for a fucking trainset i don't know. but probably not, i would expect a dpdt changeover for direction and a dial on a trainset. but you never know

File: 19700103_215245[1].jpg (614KB, 1600x1200px) Image search: [Google]

614KB, 1600x1200px

>>1192494
>bench power supply
Thank you anon. After looking at it again, I can barely see the description of the holes on the top.
The most right one reads 12 V and the most left one reads 0 V. Unfortunately I can't read the ones in between.
Found something on the back.
It's from a school, department 'Polytechnik', which was a subject in east germany. It also reads 26 October 1977.

File: Pioneer SX-990 Preamp.png (32KB, 946x551px) Image search: [Google]

32KB, 946x551px

I'm repairing an old SX-990 receiver and narrowed down the issue to the first transistor in this diagram. I have misc. transistors on-hand, but what are the important parameters to match with audio?

File: ecb.jpg (3KB, 130x117px) Image search: [Google]

3KB, 130x117px

>>1192557
low noise, high B at low current, pinout ecb
equivalent BC549C (pinout cbe)
2SC870 would be BC549B

File: 35057832.jpg (70KB, 366x374px) Image search: [Google]

70KB, 366x374px

What's the smallest motion sensor circuit I could make?

File: small PIR sensor.jpg (98KB, 604x127px) Image search: [Google]

98KB, 604x127px

>>1192651

does google not exist in your country?
http://jeelabs.org/2012/03/17/another-pir-sensor/

>>1192651
I'd say an IR LED and a IR sensor. If you tune it properly and add an opamp differentiator you could get it to make a pulse on both rising brightness and falling brightness. Throw that into a comparator (or two?) and use a voltage divider (or two) to go high when the voltage spike reaches above a certain threshold, triggering a flip-flop or latch or something and activating your alarm. If you can manage SMD soldering then you can essentially buy the thinnest components possible and fit the whole thing into an 8x8x10 mm volume or so, but it really depends on your ability to solder small components. Using only through-hole components, I'd say you could get it 10x12x30mm with a few creative layers of heatshrink, not including the power source.

File: 1102.png (17KB, 180x200px) Image search: [Google]

17KB, 180x200px

>>1192580
Tossed in a S9013 to both sides and it works like a charm. Thanks!

>>1192146
I'm trying to test the shift registers, but I can't simulate clock pulses with a couple of wires very well. When the CLK input isn't high it's in one of those shitty intermediate voltage states, so I have to set it low, but I don't think I can do so quick enough for it to trigger the rising edge. I've got a board full of inverters (the 74HC04s aren't actually dedicated inverting buffers, which I probably should have known), how can I simulate an instant low-high transition? I tried using the inverters as some sort of buffer, but they've got that shitty intermediate state too.

Is this a problem with all HC chips? I've worked with LS before and never had this problem, albeit it was on a board with it's own clock buttons.

File: e67_1.png (47KB, 800x386px) Image search: [Google]

47KB, 800x386px

So: superconductors. I'm going to try and attempt to make a "magnetic hose" using copper wire and aluminum tinfoil, which (in theory) when cooled with liquid nitrogen will act as a superconducting magnet. I'm then going to apply three phase 220v mains power and see what happens. The "magnetic hose" will be inserted into a 2" metal pipe, which itself will be surrounded with about 12" of insulation. I think that'll be enough just to get results.

Also before whining about safety: I myself installed the line I'm drawing from so I know what I'm doing on that end.

>>1192730
Aluminium becomes a superconductor at 1.2K, and copper doesn't become one at all. Back to the drawing board?

>>1192730
Also you'd better make sure your reactance is high enough otherwise you'll trip a breaker.

>>1192737
And also a type I superconductor, with a really small critical magnetic field H.

>>1192726
HC means CMOS, right? There shouldn't be an intermediate state, CMOS transfer function is very steep. I would expect you to get a kind of chatter/bounce that turns every unclean 'edge' into a bunch of clocks. Get a schmitt trigger input gate to clean it up, or debounce.

>>1192730
If you want superconductivity at liquid N2 temps, that means YBCO. Dunno what you're thinking. Also, it's been awhile but I if I recall correctly superconductors are not great with AC, just think about what happens to those flux pinning vortices.

May be a stupid question but do capacitors matter what theyre made of as long as the ohms is right and can accommodate the voltage?

File: IR_transmitter.png (14KB, 633x216px) Image search: [Google]

14KB, 633x216px

>>1192726
>problem with all HC chips?
No, it's a property you will understand when you compare the input structures of TTL and CMOS. In a nutshell, an open TTL input is HIGH while an open CMOS input is undefined because it is static (capacitive) and can have any state. You never leave a CMOS input open.

The image shows a circuit (part of my Theremin project) that is easy to modify for generating a clock signal. Leave off the driver part (4 components) and change the frequency as you need (f=1/t). You can have one pulse per second or you can have 32.768 kHz (approximately..). With one buffer after the oscillator you can have both with a single HC04. Without the buffer you can have three independent clocks. If you want a reliable clock button you will have to 'debounce' the switch, else you may get an unknown series of pulses each time you push or release the button.

>>1192766
>>1192801
My indicator LED flashes and shit, it looks fucking terrible, but since I'm not putting the wrong voltage anywhere I can't be doing permanent damage, right? I bought 74HC04s instead of 74LS04s because I thought they would handle the MHz frequencies better, but that might have been a bad idea.

If I use >>1192146 or >>1191694 I shouldn't get the problem from the crystal, right? So all I need to do is "debounce" the button. A couple of simple BJT-based inverters should do the trick, right? I could buy the 74LS04 or an LS buffer or something along those lines, but I've got 100 BJTs lying about that I'm not going through any time soon. I could also try some sort of BJT-based buffer, if a simple one happens to exist.

While I'm here, would you recommend ammonium persulfate or sodium persulfate? I'm going to try to electrolytically refresh the etchant, which hopefully happens instead of producing oxygen gas.

>>1192827
Which shift registers are you using?

>>1192839
74HC164 8-bit SIPO registers. I bought 10 of them, so you'd better not tell me to get anything else.

File: IMG_1771.jpg (796KB, 3000x2000px) Image search: [Google]

796KB, 3000x2000px

why is /diy/ such a huge clusterfuck?
but nvm, I just post here. Not much electronics yet, but whatever.
Building a kind-of-big 7-segment-display.
Every number is around 20cm big. Kinda fucked up cuting the numbers in wood, but it works.

It will be a countdown timer for an even we are planing in my garden. Only need 3 numbers. Would be nice if a fourth would've fit onto it, so I could use it as a clock afterwards, but that didnt fit and I was too lazy buying a different piece of wood. webm incoming

File: wedidit.MOV.webm (572KB, 1280x720px) Image search: [Google]

572KB, 1280x720px

>>1192910
to controll it I'll just throw a raspberry with a few 74hc595 shift registers at it.
Kind of overkill, but I want to control the countdown via smartphone and for this the raspberry will be handy, I think.

File: IMG_1782.jpg (970KB, 3000x2000px) Image search: [Google]

970KB, 3000x2000px

>>1192911
now just gotta wire up 14 more led strips, design a PCB, echt that shit and wire everything up.

My microwave tripped the GFCI after I warmed a meal (as in a few seconds after it beeped that it was done) and now it shows low (~300K Ohm) resistance between the leads. Anyone have an idea what it might be? Should I try to fix it or just trash it (/tear it down for parts)?

I have a switch rated for 220VAC 10A. Can I use it for 120VAC 15A?

>>1192994
You can if contact lifetime is not an issue. How often do you really switch 1.8kW?

>>1192994
No, it exceeds the current rating.
The current rating is about how much heat it can dissapate.The voltage rating is about the switch not arcing.
The switch has to meet or exceed both values

>>1192970

a microwave is an always-on device, so its normal to see a resistance between the power pins. just ignore the breaker and use as usual. move it to a non GFCI plug if it continues.

>>1193005
Slight error: there's a fairly low resistance between the earth and the leads. Maybe some liquid food spatters created a short. I'll let it sit for a while and see if it's still the same tomorrow.
I wouldn't be able to use an ungrounded outlet anyway as I live in europe in a modern house. All outlets are grounded, and for good reason.

>>1193003
Right. That's what I thought. But I also had a little doubt that it was total wattage that was important.

>>1193002
Every time I turn on my Freude router, which says 15 A on the label.

>>1192767
I reitterate. Do capacitors of different materials but same farads and voltage work electrically the same?

>>1191671
Like >>1191687 said, keep your tip clean. It makes things a thousand times easier. Always remember that soldering is all about wetting and heat transfer.

Google "nasa soldering standards" or something like that, and read that document. It's totally overkill, but the practices are sound, and it will give you a sense of what to aim for!

>>1193030
First order of approximation : yes
Second order of approximation : no, because they will have different ESR, lifetimes, environmental protection, etc.

Without context, we can't know if this is important to your application.

>>1192970
300k (K? lol) ohm is < 1mA. which is nothing.
but GFCI won't trip because of L-N faults, they trip because of L-E or N-E faults.
Ideally L-E or N-E of an appliance should be infinite on a multimeter.

>>1193012
no that does not sound like a food splat issue.
i absolutely doubt that
1) food could get anywhere near the electrical gubbins area
2) there would be for any concievable reason a large enough area of live conductor exposed to allow a short to occur

either throw it out or open it up, don't keep using it and don't cross your fingers and bury your head in the sand.

>>1193030
no they leak differently too.

>>1193012
the only way most circuitry can ever connect to earth is through Y capacitors or bridging to the chassis. if you open it up you can look for damage, debris, or fluid that could be the culprit. it may be symptomatic of another issue.

i believe that some parts of a microwave chassis can be live so probe continuity before assuming you've found a short because the hv diode is bolted right to the metal.

>>1193079
also having disassembled two microwaves, getting them apart can be a pain in the ass and may be an irreversible process depending on how badly you manage to bend the sheet metal or snap plastic clips. don't take it apart unless you're ready to get a new one.

File: switch capacity.png (57KB, 801x310px) Image search: [Google]

57KB, 801x310px

>>1192994
>I have a switch rated for 220VAC 10A. Can I use it for 120VAC 15A?

Most switches have a higher current rating for 120v than for 240v.
Look at the switch carefully and you may find it embossed or printed on the switch.

>>1193162
It's Chinese. Bought off eBay. It only has 220/10A rating markings. Imma get something rated 15A

>>1192726
Resistor + capacitor filter + pull up resistor. HC is reasonably fast and high input impedance, switch bounce will be an issue.

>>1192911
For easy WiFi I like using ESP8266 boards, super cheap, pretty easy to program.

File: IMG_0959.jpg (895KB, 3264x2448px) Image search: [Google]

895KB, 3264x2448px

Never take apart one of those 12V LED light-up buttons. 30 minutes in and it shows no signs of going back together. I'll just buy another and run the internal LED off 5V instead; even if you do take them apart, the internal LED+resistor is completely sealed off.

>>1193286
I took it even more apart, it's dead now. Would you believe it cost $15?

Anyone own a UNI-T UT210E clamp-meter? I'm considering getting one because it's got auto-ranging, true RMS, AC and DC current, and a capacitance-meter.

>>1193286
>>1193292
Ok, you don't actually want to take the bottom off, you instead pull the top of the button off to access the LED. You probably can't desolder it without fucking everything up, but it does have a tiny 820Ω resistor inline with it. More interestingly, it's a bi-directional LED, so the polarity doesn't matter. Time to lose more money.

>>1192827
>A couple of simple BJT-based inverters should do the trick, right?

Yeah, with the right RC filtering.

>>1193325
>RC filtering
I was only going to use them on the button, not the crystal itself, will I need something similar for the crystal?

File: web8.jpg (91KB, 800x683px) Image search: [Google]

91KB, 800x683px

>>1193300
>Anyone own a UNI-T UT210E clamp-meter?
No, I don't, but there's a review at https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/
I would prefer the more expensive 6000 count UT211B. For measuring small currents you better use a standard multimeter.

>>1193336
>something similar for the crystal?
No, oscillators do not bounce, only mechanical contacts.

>>1192146
What's the idea behind using a shift register as a frequency divider? How do you handle the data and clear inputs?

>>1193349
I'm using a 2mm-travel ~2N-spring-strength momentary button with no detent, so there shouldn't be any bounce.

>>1193354
Clear remains inactive, run the frequency into the CLK input, and put the inverted parallel output of choice back into the input. Once the inverted output gets enough clock pulses to make it to the selected output (selected by fucktons of rotary switches), the output flips polarity. This output is then fed into the CLK input of the next register.

>>1193354
The shift register is just an implementation detail. You should be asking what's the idea behind ring counters.
https://en.wikipedia.org/wiki/Ring_counter

File: 1455124111002.jpg (98KB, 480x480px) Image search: [Google]

98KB, 480x480px

>get interested in electronics
>acquire bunch of equipment (got a sweet scope for free)
>buy €300 worth of shit on aliexpress
>bursting with ideas
>start a bunch of projects
>feel like I understand all the shit I learn
>have tons of fun
>2 months later
>no motivation to do anything with it anymore
>no ideas
>feel retarded
the fuck is the matter with me

>>1193372
Acquire a bunch of equipment? That's your problem. You've gotta build your tools, it gives you a real sense of achievement once you've completed them and actually use them.

>>1193372
Everybody has had this. Just stop doing stuff for a week, maybe 2, and you will regain interest and enthusiasm. Or just power through the dip and complete a project, the sense of achievement will re-invigorate you.

>>1193372
Put everything away and clean your work area.
Nothing inspires me to make a mess working on something like a pristine work area.

File: sweet vape bro.jpg (153KB, 691x655px) Image search: [Google]

153KB, 691x655px

I was repairing a desktop "herbal vaporizer" (I did get it working again), and I decided to have a go at reverse engineering it.

The board itself is tiny. The only control on the front of the device is the switch/ 500k potentiometer.

I'm just wondering if this schematic even makes sense?

I haven't messed with triacs very much (although that was actually the component I replaced on the board to repair it, just had to solder on a new one).

I'm guessing that the heat dissipated by the ceramic heating element is a function of the AC voltage applied to it, so I was thinking that this might be some kind of rudimentary phase angle control circuit when I saw the triac, but it doesn't really look like that...

I'll post the PCB itself next.

File: fowr twenny blazit.jpg (715KB, 2338x1602px) Image search: [Google]

715KB, 2338x1602px

Sorry if the components are hard to see. In my schematic, I also disregarded one of the resistors in series with the 500k ohm for convenience.

Not sure if /ohm/ but how could I calculate the required power for a given range for an FM transmitter?

>inb4 FCC gon getcha

I only want to build something that will get around my house and to the end of my garden, if the gubmint come at me I'll just go underground and become a domestic terrorist for kicks

>>1193292

>$15

https://www.banggood.com/search/angel-eye-button.html

File: aewrtetea.jpg (3MB, 1620x2880px) Image search: [Google]

3MB, 1620x2880px

Hello /ohm/. I don't have a clue about electronics. I come looking for help, because I can't enjoy my anime intros like this.
I have these cheapo pc speakers, where the sub and sats aren't separate, but connect to the persocom with one 3.5mm. Problem is, the sub hums LOUD. The hum goes away if I remove this red/black cable from the board, but my lower frequencies accompany him. How can I have both good bass and at least 75% less hum?
Pic is it

>>1193366
>so there shouldn't be any bounce.
mechanical switches *always* bounce

File: honest crocodile.png (168KB, 590x475px) Image search: [Google]

168KB, 590x475px

>>1193372

>get EE degree
>teaches me fuck all about actual electronics
>built some kits, do some instructables, start learning things, be super bad at it
>oh no, am I retarded?

the answer is yes

File: Bildschirmfoto vom 2017-06-14 19-53-27.png (191KB, 524x406px) Image search: [Google]

191KB, 524x406px

>>1193380
this
https://www.youtube.com/watch?v=BBR5v89L6gk

Could I use an old water tower as a hydro storage battery? Would it be a functional idea to just put a shitload of windmills on and around it to power a pump to get water back up there, and use the tower as a steady, constant flow?

>>1193552

Sure. It won't be hugely efficient, since you're going to be losing energy pumping it up there and again when you pour it over your screw or turbine or whatever, but if you're using something like wind then that's not going to be a huge concern.

>>1193579
Yeah. I'd imagine it'd lose a lot of energy, but at the same time once it's established it'd take almost zero upkeep. And it'd be constant, assuming you're always pumping more up than it drains out. All you'd have to do to ensure that is just keep enough windmills hooked up to enough pumps.

File: lamp-dimmer-circuit.jpg (130KB, 603x303px) Image search: [Google]

130KB, 603x303px

>>1193433

your schematic is wrong and i dont have the patience to fix it for you, but it looks very much like a standard triac dimmer circuit. (you have 120Vac going directly into the gate, which is absurd)

>>1193603
Meh, i tried. I know it doesnt make sense to connect the gate to AC, but that appears to be how it's wired.

I've checked the datasheet of the triac and, indeed, pin 3 is the gate - which is connected to one of the AC lines

Thanks for the dimmer schematic tho

File: 1497452330840.jpg (125KB, 691x655px) Image search: [Google]

125KB, 691x655px

>>1193433

more like this

>>1193443
>required power for a given range for an FM transmitter
The antenna and coupling of the transmitter to it has as much to do with range as power.

>>1193627

yeah, it looks like the dude cant into reversing viewpoint. pin 3 is the innermost pin, which is connected only to D3, not the AC line.

>>1193372
I know what you mean. I'm waiting for a special-size servo to arrive for my project. There's loads of other stuff I need to do, but I just don't have any interest, so I tell myself I'm just waiting for the servo to arrive instead.

>>1193552
For a more effective solution, see if you an find a stream or small river, that travels down a fairly steep hill. One you do, build a wall around it, to force it to collect in a pond. Then make a hole in the bottom of the wall and put a turbine in it. Add a sliding door at the back to close the turbine off when you don't need power.

Anybody use a pair of these wire strippers? Just wondering if they're any better than those mechanical contraptions.

File: Clive's stripper.jpg (49KB, 1000x1000px) Image search: [Google]

49KB, 1000x1000px

>>1193725
I'm gonna neck myself.

File: 46684.jpg (60KB, 800x800px) Image search: [Google]

60KB, 800x800px

>>1193725
>>1193726
Just get yourself one of these motherfuckers. No adjustment needed, and no risk of cutting the wire like with the one you linked. Plastic ones cost next to nothing and work just as well.

File: P70615-163731.jpg (102KB, 936x702px) Image search: [Google]

102KB, 936x702px

>>1193300
I do, quite like it.

>>1193552
Water towers don't hold a huge amount of energy, assuming 4Ml at 40m up that's ~400kWh, enough for about 8 minutes worth of energy of a typical 3MW wind tower.

Pumped hydro schemes are usually done using rather large lakes at each end.

Best way to realize very high Q filters?

I need a filter with a center frequency around 50kHz (I have some play with this value but it needs to be above the audio range >20kHz but not so high frequency that I need to start worrying about parasitic capacitance and inductance ruining my day) and a bandwidth of no more than 20Hz. The roll off needs to be very sharp, almost an ideal filter. I need to be at my noise floor of -70dBV just a few Hz outside of the passband. Also the passband needs to be as flat as possible. Only Butterworth and very low ripple Chebyshev filters are acceptable.

I know active cannot do this with active filters so I'm pretty sure I'm going to need some passive LC filter network but I'm just worried about component tolerances and temperature having a dramatic effect on the filter characteristics.

Can I use a cavity resonator? I know they usually have very high Qs. Do they make them for such low frequency applications or is the wavelength too long to allow for a reasonable size?

>>1193859
Crystal filter would be the classic choice. Or you could consider mixing the signal down to ~0Hz and using a low frequency low pass filter. Or, since it's year 2017, DSP is an option too.

Your goals sound misguided, though.

>>1193859
That's pretty much impossible with real world components. DSP maybe.

>>1193868
Crystal filter looks like it might work okay, I'll give that a try. I'm trying to design a swept tuned spectrum analyzer but it's primarily for audio frequency and not RF. This bandpass filter is the IF filter. I need a narrow resolution bandwidth which is why I have such insane requirements for the Q. The analyzer basically needs to be able to distinguish frequencies down to the lowest audible frequency.

I could have just gone for discrete bandpass filters or FFT but this provides a more unique challenge.

>>1193859
You could use a very extreme LC filter. Since reactance scales proportionally to inductance and inversely proportional to capacitance, find yourself a massive inductor/transformer/solenoid, and couple it with a very small value capacitor. You'll want to install a little hand-wound inductor in series with the main one just to tune it.

File: clock_crystal.jpg (6KB, 282x193px) Image search: [Google]

6KB, 282x193px

>>1193875
What about a handful of dirt cheap 32kHz clock crystals and a ladder filter calculator?

File: 1490563508761.png (866KB, 800x1200px) Image search: [Google]

866KB, 800x1200px

>>1191510
Trying to make a UAV, and I need to start building the remote control.

If I want to take some pot values and send them over 2.4GHz wifi, will I need a microcontroller of some kind or is there a different way to do it? I'd somehow need to convert the signal to the correct requirements to be sent over WIFI and then output it, and the only way I can consider that is by having a microcontroller.

I'm not a fan of having a microcontroller as part of my RC for aesthetic reasons though. Anyone got any better ideas?

>>1194089
buy a fucking rc system. Shit is cheap today.

File: 1307474323794.jpg (27KB, 293x473px) Image search: [Google]

27KB, 293x473px

Question for electronics bros. I recently started learning about circuits and troubleshooting since I would like to purchase some old consoles and fix them up. One of the tools I recently purchased is an auto-ranging digital multimeter.

To test it, I've set the meter to voltage and selected DC. I opened a package of AA 1.5v batteries and tested one, positive test probe to positive terminal and negative test probe to negative. The result was 1.563v, excellent read, battery is clearly charged. I then tested a battery from my audio system remote and got the result 1.494v, makes sense, the batteries in that remote have been used for a while now.

Here's where I'm scratching my head:

I have an Xbox 360 wireless controller that uses 1.5v AA batteries. I haven't used that controller in about 3 years but out of curiosity, I decided to test the batteries. There was no sign of corrosion on either the batteries or the contacts in the battery holder so I went ahead and tested them. The result was 126.8v.

What gives? The batteries are just disposable Energizer AA rated at 1.5v and they haven't been used in around 3 years. Anybody have any ideas? Google and Jewtube have been no help in figuring this out.

>>1193717
The feds will 100% crawl directly up your ass if you touch even small streams going through your own property. You will die bankrupt paying fines.

>>1194124
>auto ranging
There's your problem m8y

>>1194136

If that's a problem, why did all the other batteries I test read just fine. Even the built in rechargeable battery pack from my PS4 controller tested within it's ratings.

File: $_32.jpg (15KB, 500x500px) Image search: [Google]

15KB, 500x500px

>>1193726
>>1193725
get these: >>1193732
i have the same as in you picture and used them like 2x
i use pic releted ones scizor like they are good too

File: fizzbuzz.mp4.webm (943KB, 1920x1080px) Image search: [Google]

943KB, 1920x1080px

we have 3 numbers now and can do fizzbuzz! Moving on in big steps!

green led = fizz
blue led = buzz

File: IMG_1883.jpg (586KB, 3000x2000px) Image search: [Google]

586KB, 3000x2000px

>>1194158
next step is either programming it the way I want to have it or designing a PCB first. Prolly designing a PCB first and wire everything up nicely

>>1194124
>The result was 126.8v.

nope, it read 126.8mV, meaning ''it's dead, jim.''

you can avoid this kind of confusion by (1) paying attention, or (2) using a non-auto-ranging unit. i hate auto-ranging with a passion coz it takes longer, and you always have to double-check your measurements.

File: IMG_20170615_174619.jpg (2MB, 2592x1944px) Image search: [Google]

2MB, 2592x1944px

>>1193934
I'll probably end up using 32kHz crystals but I don't have any on hand at the moment so I'm trying to characterize a 4 xtal ladder bandpass filter using 8MHz xtals. I'm definitely getting a better Q, around 26000, but I'm not sure why I'm getting -23dB of loss and idktf is up with this phase response. Is this normal?

File: file.png (8KB, 513x273px) Image search: [Google]

8KB, 513x273px

This schematic interfaces a serial port with a PIC microcontroller. I'm pretty sure the caps on the bottom are a charge pump to get up to the 12V programming voltage. Can I use a smaller capacitance for C2 so I can get a ceramic cap instead of an expensive tantalum cap? What value would be reasonable?

Also, I'm thinking of making a vaporizer that automatically turns up the temperature as the material is vaporized. I want to do it by sensing the air that leaves the oven and turning it up when there's no herbal fragrance being released on a draw. Would a humidity sensor or optical, like in a smoke detector, make more sense here?

Wait instead of having to design an ultra narrow-band filter can I not just frequency translate the signal to a higher frequency and then scale it?

Like if the audio frequency is 20Hz to 20kHz then it has a bandwidth of 19980Hz. Let's translate this up to some frequency, say 100kHz so now our audio signal is between 100kHz and 119.980kHz. But then we scale it, let's say we double that range so it runs from 100kHz to 139.960kHz. This should allow me to use lower Q filters because now the RBW only needs to be 40Hz instead of 20Hz. If I scale even more I can get an RBW of several hundred Hz easily.

Maybe this is retarded, I don't know but there has to be some frequency scalar circuit. Like if I sweep the input from 1kHz to 10kHz and design if so the output will scale that by 5 then on the output you'll measure a sweep from 5kHz to 50kHz.

>>1194310
I don't think there's an analog circuit that would do that. A PLL would work if you were trying to multiply one frequency but for a signal like audio, no way.

>>1193465
How should I filter a single button push? A tiny cap to ground and a resistor in series? Or a big inductor in series?

>>1194344
The former. You're making a low pass filter. Pick an RC with an appropriate time constant - maybe 1/10th of a second.

>>1194345
Is 1/10 enough? There's no detent in the button, so the only bounce will be on a very small scale. Wouldn't it be much better to make a high-pass filter with a really short RC so that only one really quick clock-like pulse makes it into the IC?

File: switch debounce filter.png (184KB, 1264x675px) Image search: [Google]

184KB, 1264x675px

>>1194344
>How should I filter a single button push?
>>1194358
>Is 1/10 enough? There's no detent in the button, so the only bounce will be on a very small scale.

Are you in China where Google is blocked?

>>1194310
Frequency multiplication for signals you want to be linearish isn't really possible.

And wouldn't help that much anyway, you're limited by dB/octave both of which are log scale.

>>1192503
Open it

>>1194345
>>1194371
I don't think debouching is the problem, at least not at the moment. Trying one of those circuits and I can't get the register to clock at all, even when ground should be directly referenced as pic related. Using a 820Ω also did not work, should it be lower still?

You'd think that since I'm using a twisted ring divider, that the output (the last output pin that I'm feeding into the inverter) would be high half the time due to an uncountable number of unwanted clock pulses, but here it's staying low, as are the other outputs. Any thoughts?

File: switch.png (3KB, 400x400px) Image search: [Google]

3KB, 400x400px

>>1194425

>>1194425
>Any thoughts?

yeah, you've obviously screwed something up. use and inverter chip connected to an LED so you can visualize what's going on. darken to the room lights so you can see if the LED flickers even for an instant. in short, you're the most likely person to help you coz you're there and we're not.

File: schmidt debounce.jpg (19KB, 315x186px) Image search: [Google]

19KB, 315x186px

>>1194425

another thing is that a number of chips refuse to operate if the inputs have too slow a rise-time. so, a debounce cap will screw things up unless you use an external gate, preferably a Schmidt trigger one, to square up the pulse.

>>1194442
That's what I was thinking. But that's only on the clock edge, in this case I assume it's rising edge. If I get the logarithmic decay on the falling edge then it doesn't matter. Though I guess it's that logarithmic function that smooths out the bouncing in the first place.

I'll have to look into Schmidt triggers, before that I should figure out why I can't clock it by touching two wires together. My breadboard couldn't have enough capacitance to make the rise-time too large, right? I'll try another of my 10 SIPOs to see if I fried this one. How careful do you have to be with CMOS ICs compared to Schottky ICs?

>>1194302
Why not a standard electrolytic?

>>1194429
1-10k is typical.

>>1194252
Your phase is wrapping, if that's what you're asking. Did you cal your network analyzer?

>>1194480
I'm pretty sure it was an issue with the number of data points in the sweep. I didn't realize I had it set low, about 100 points. Maxed it out at 1600 and all the weird phase stuff went away and I got a more normal response. I also probably had the IF bandwidth set too high. I did run a response cal on it beforehand.

I'm still a bit new to using this and Agilent's documentation is surprisingly lacking. Just enough to get you up and running and that's about it.

>>1194450
> If I get the logarithmic decay on the falling edge then it doesn't matter.
Unless, of course, there's noise in it which registers as a series of rising edges. Your overly large pull-down resistor worsens the situation.
Not that the rising edges produced by >>1194429 are clean either.

Several people have told you to debounce your clock properly. Why aren't you listening?

>>1194540
I was just trying a few bootleg methods that don't include going out to buy any parts. But before that I still need to figure out if my current methods will work, because at the moment it's not picking up a single clock pulse regardless of method. Anymore. In the case that I've buggered it then I'll have another thing to buy, and in the case that it works, I can test the bootleg methods again to see if any work. I wonder if this counts as study for my electronics exam on Monday?

File: 1463296206561.jpg (31KB, 600x600px) Image search: [Google]

31KB, 600x600px

>>1191510
I want to get a little servo motor to push the button on my kettle. Gonna hook it up to a TI MSP430, and a power source with a little mini breadboard, and cover it in plastic. Total NigRig.
What do I need to buy?

I think a stepper motor will draw too much power.

>>1194550
Certainly you have at least some gates or 555s? 2 x NAND or 2 x NOR would make an SR latch, 555 could be used as a monostable, etc.

> it's not picking up a single clock pulse regardless
Is the shift register powered?
Is the reset pin connected properly?
Is the data inputs wired properly? (pins 1 and 2 are ANDed internally).

File: CE-3 schematic.png (446KB, 1458x972px) Image search: [Google]

446KB, 1458x972px

I want to convert a Boss CE-3 to a CE-2, because it's almost the same schematic, and the CE-2 is about 3x the price of a CE-2. Now I replaced all the different components, but to my surprise the CE-3 has a diode (D10) to ground on the MN3102.

Now my question is, does that diode affect the sound in any way? What does it do?

File: img.jpg (135KB, 1600x900px) Image search: [Google]

135KB, 1600x900px

Even though it was just a quick fix for a laptop charger cable, I always feel like there's something romantic or meditative about it

File: hint.png (63KB, 760x174px) Image search: [Google]

63KB, 760x174px

>>1194780
>What does it do?
It lifts the GND level of IC4 and thereby the Vgg output (pin 8) for the BBD supply voltage in case IC3 is not manufactured by MEC. There's a hint in the datasheet (pic).
>does that diode affect the sound?
Not directly, it belongs to the digital side that clocks the BBD and ensures proper function. Be the first to try it out!

>>1194796
>about it
about what?

>>1194817
Late night soldering under a desk lamp that's too bright, tools and scraps all over the desk

>>1194555
What sort of power supply do you have?

9g RC servo would be an appropriate size IMO.

>>1194480
I'd save a buck or two with ceramic over electrolytic.

File: power supply.png (387KB, 600x393px) Image search: [Google]

387KB, 600x393px

>>1195131

ceramic caps only go up to about 1uF. you need 100x that.
you can pull electrolytics out of all kinds of old appliances, including small DC transformers, whether old-iron or switched.

Any advice how to do bga by hand? I am able to remove chips and clean them from boards, but I haven't yet figured out how to reball them. I have a heat + solder station, vise, and solder paste available.
If I just apply a very thin layer of paste onto the bottom of the chip and then heat it with low air flow, will that work? It failed by just forming 3 large solder balls last time I tried, but I think I applied too much paste

I want to be able to do this by hand and without spending hundreds of dollars

>>1195403
Have you tried building a stencil to put paste on the pcb?

>>1195437
I haven't. Wouldn't I need to use a cnc router for that, or should I just buy a stencil? 324 pin, 0.8mm pitch (I think). It's csg324 for a Xilinx artix 7 75

>>1195444
You might make it some of the same ways people make homemade pcbs using a subtractive process. You would do something like print out your design, transfer it to the metal, and then use a chemical that eats the metal everywhere the ink wasn't transferred.
Google would know more than me.

>>1193050
Most NASA things are overkill (I've gone through their clean room, flight critical hardware and ESD trainings) but they are there because someone fucked up and they found out they could've prevented it.

Like the robot my coworkers blew up last year because the manager had explained to them multiple times that it was not the correct way to charge the batteries but they ignored it.

https://youtu.be/JECJAgRsp-4

are mosfets better than resistors in making dummy loads?

>>1195464
What kind of dummy load? If you need a constant current load a resistor alone isn't going to work.

>>1195465
yer CC.

>>1195403
Even the Chinese use jigs to reball. You should be able to get them for relatively cheap

File: s-l400.jpg (30KB, 400x400px) Image search: [Google]

30KB, 400x400px

>>1195489
You mean like this?

>>1195500
Yeah.

File: 1439303084406.png (161KB, 500x283px) Image search: [Google]

161KB, 500x283px

>>1195457
Reminds me of some industrial tools:
>dad works as a millwright
>he's told batteries die very often there
>checks the charger
>black fucking spot on the circuit board
>they knew about it already
>"it still lit up when we put the battery in"

>>1195379
Bigger ceramics do exist, so long as you don't need particularly high voltage ratings. 15V 100uF ceramics are still pretty cheap.

>>1195590
Well, yeah, but he wants to use ceramics because 100u/40V electrolytics are too expensive. At that level of jewery he should salvage the capacitors.

File: FET.jpg (25KB, 843x390px) Image search: [Google]

25KB, 843x390px

Is this the correct way of turning on a n-channel mosfet? i am worried its going to send 400W from V2 into V1 and release magic smoke. It wont go boom right? V2 is a 6s lipo and V1 is just supply/control for mosfet. not sure why resistor is there but was told it was needed for in rush current or some crap.

>>1195624
Some extra info. the top of mosfet is drain, gate and source is on bottom. V2 + goes to drain and V2 - goes to source.

>>1195624
why are you using a mosfet to short out your power supply?

>>1195626
discharging my rc lipos quickly if i dont end up using them all and i think i could use it to measure battery performance by measuring the voltage drop on large power draw.

>>1195629
next thread:
>i burned my house down, what do?

>>1195631
Hahahaha

Ill use a fuse. No really, this isnt bad as it sounds

>>1195646
You sure? Is that weird 5.7V chosen so that the mosfet draws "just the right amount" of current? That doesn't really work.

Has anyone used ngspice before?

I've read a dozen docs and I still don't understand why my circuits fail at run time

File: A-B Switch.jpg (3MB, 5312x2988px) Image search: [Google]

3MB, 5312x2988px

Looking for some advice. Made this A-B audio switch a while ago, but now the switch is failing.
I've got more of the same DPDT switch, but I don't want to replace it with that, because when switching, it creates a bunch of static. I've heard of make-before-break switches, but I'm not sure if that's what I need.

Mostly just looking for a replacement that's not crazy expensive, small, wont have that static issue, and where to find it.

>>1195649
5.7 is probably chosen so that each LiPo cell only discharges down to 2.85V.

>>1195778
…that's not how it works

File: lipo-test.jpg (21KB, 666x239px) Image search: [Google]

21KB, 666x239px

>>1195624
You cannot simulate ignorance. Just solder the red to the black wire, watch them explode and collect your Darwin Award.

>>1195656

1 - if you use cheap switches and jacks, you'll get scratchy sound eventually, no matter what.
2 - when you switch over, you're often switching in a series capacitor that's charged. and then cap will discharge into the load once the connection is made, causing a scratchy sound. depending on the application, it might be worth trying to put a constant resistor load on both sources. make it about 5x the size of the normal load.
3 - you might wanna replace the switch with a dual balance pot. turn left and you hear one source, turn all the way right to hear the other. turn half way to hear both. finding the right value pot is left as an exercise.

>>1195590
I don't need 40V. The question is whether lowering the capacitance will make a real issue in this application, as I could then use a ceramic cap with a high enough rated voltage to work (15V+).

>>1195820
This.
Terminating all connections is always a good idea.

There's a way to de-scratch audio connectors: ethanol (or isopropanol) and a paper towel to clean the plugs. Grab them with the wet towel and turn left and right for a while. Put a drop in the jacks, plug in, rotate, disconnect, plug in again, repeat, let it all dry.

The switch usually prevents access to the contacts. Put a drop into where the lever comes out and switch back and forth a few times, let it dry. Even scratching pots can be silenced that way. I just applied such a procedure to the range switch of my multimeter because the current range had developed a series resistance between 5 and 10 ohms, depending on the exact position of the rotary switch. Now it's about 1 ohm as it should be.

>>1195838
It is already a bit iffy circuit and by reducing the capacitor you reduce the (peak) current available for programming. This also depends on your serial port.
It's not that too small capacitor really breaks anything. It just makes the programmer non-functional or unreliable.

>>1191510

Thank you guys for helping the community.

I have an issue that is puzzling me.

I have a 10.8v DC motor connected to the output of a step down buck converter module from ebay, and the input of the buck converter connected to a 32v 625ma power supply from an HP printer.

I am trying to automate the spinning of this motor via a web controlled 120v outlet the power supply is plugged into. This part works.

The issue is that with the motor connected, the power supply will not 'turn on' when plugged in. It will only pulse the motor and the green light on the power supply doesn't turn on.

If I plug the power supply in with the motor disconnected, then connect the motor then all is fine and the motor starts off without issue.

It seems that having the power supply connected to load when its plugged into 120vac stops it from turning on fully. It only outputs 100-150ma @ 32v in this state. Disconnecting the motor, allowing the power supply to 'turn on' and reconnecting also works. It seems to be put into some kind of gimp mode.

I'm thinking some sort of capacitor between the power supply output and buck converter input might work but I'm not sure...

Any insight or ideas are greatly appreciated.

>>1195890

Your boost converter + motor are most likely overloading the HP supply before it can reach full voltage.

The quick and dirty solution would be to put in a relay to delay the switch on of the buck, can use a cheapo module like this https://www.aliexpress.com/item/Free-Shipping-DC-12V-Delay-relay-shield-NE555-Timer-Switch-Adjustable-Module-0-10S/32553941426.html + a 12V linear regulator or design your own.

>>1195890
Maybe consider that the converter is not able to supply enough in rush current to the motor when the load is first connected to it. the rotational. Inertia of the rotor is the cause of this. Assume 5 to 10 times the nominal current of the motor when sourcing your power and step down converter

>>1195778
5.7 is the right current draw for that mosfet. More volts more current goes out of lipo and dissipates into heatsinked mosfet. I might just stick to resistors etc then since people disagree with this method.

>>1195930
Don't trust a MOSFET to be linear, just go with a stack of power resistors.

>>1195934
This. If you actually want a constant current drain I'm sure there are better ways of going about it.

>>1195934
>>1195952
I guess that is why i couldn't find much people using them for linear loads. Ill stick to using power resistors. Thanks guys

>>1195930
http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/

Try that. I don't remember using it high power, but I was stepping down like 15V to 2-3 and it was constant current. Test it first, I think the transconductance of the mosfet can make a huge difference from his simple calculation.

What's cool is it works down to .5mA or less, which is what's useful for transcranial direct current stimulation. Most constant-current chips have a minimum of like 10mA

Hey guys I need a bipolar DC power supply and I was wondering what I should use when I have 1 supply? (car battery)

my input is 9-18volts

https://www.aliexpress.com/item/DIY-Kit-The-Classic-47-Amp-Suite-Headset-Power-Amplifier-PCB-Circuit-Board-Spare-parts/32803584761.html

this is very similar to what I built, mine was a different kit
I noticed this one had a picture of two 9v batteries going from positive to negative in series, but their series "connects" in the "ground" port or "floating ground" as I've read it since it is a fake ground to simulate 0volts. I'm new to this floating ground thing.

anyway


I was told to try this:
http://www.ebay.com/itm/Isolated-Power-Module-DC-DC-Converter-Input-10-8V-13-2V-Double-Output-12V-2W-/401303922012?hash=item5d6f93e55c:g:M2YAAOSwAANY5bBD

I am wondering if I can actually run that in a series? the two outputs in a series that is..
I've read I may need diodes.. if that's the only case it might be a good way for me to go.

thanks

>>1196026
Modules like this are usually pretty noisy. It's unclear from the datasheet whether the outputs are isolated from one another, which would let you 'stack' them. I would just use two batteries.

>>1196026

you can use a 7809 regulator to generate +9V for the amp and to power the voltage inverter that generates the -9V. however, your ebay link is to a module that requires a bunch of external components. so you have to make sure you get the part number, and a sample schematic for that module, or else it's useless.

i would go instead with a MAX1044 (or equivalent ICL7660) coz they're easy to find, cheap, and well documented. they only put out 10mA (or 20ma depending on the source of documentation) so that might not be enough. the MAX660 puts out 100mA but max input is 5.5V. maybe other Maxim chips can do both high current and high voltage. i'm too lazy to look thru this page https://www.digikey.com/products/en/integrated-circuits-ics/pmic-voltage-regulators-dc-dc-switching-regulators/739

>>1196037
>whether the outputs are isolated from one another
They are, the datasheet gives you the isolation rating and the leakage resistance between the outputs.

>>1196041
LT1054 has 100mA maximum output current and 15V maximum input voltage. It can also regulate its output voltage. It has somewhat higher voltage loss at low currents than the other similar ICs, though.

File: dcdc.png (36KB, 488x515px) Image search: [Google]

36KB, 488x515px

>>1196026
>can actually run that in a series?
You can. The two outputs are fully isolated and you can connect them in series to get ± the input voltage (output is _not_ regulated). The upper limit of 13.2V is a bit tight (car battery can go up to 14V) but you can reduce the input voltage with a series diode or two. The data sheet of the D121212S-2W (www.mornsun-power.com/uploads/pdf/D_S-2W.pdf) mentions output ripple (70 kHz noise) and a minimum load requirement, both of which will not be critical. What may prevent the converter from starting up at all is the maximum capacitive load of only 1µF (the amp circuit has about 100µF). There are ways to make it work though: apart from the input diode, use 100nF at the outputs followed by a 7809 for the positive side and a 7909 for the negative voltage to get ±9V just like from the two batteries.

>>1196037
well I know they are, it says so right on it..
>>1196041
=[
>>1196107
I'll be using a voltage / amperage controller to control my voltage input to this device and keep it at 11 volts, I've tested it with my car while my car can be anywhere from 12.6 - 14.4 volts depending on loudness of music and whether or not it's started, running, driving, breaks going etc.. the output is steady at 11 volts so I was prepared to have to do this for some device.

the amp works from 9 volt - 18 volt (I've tested it myself) does that change your schematic on what you would wire?

I'm kind of confused witht he 100nF things (did you mean uF?)
so basically the isolated supply can only output a burst of energy equal to 1uF so we need a capacitor 100 times greater to handle the amp's pull and I can leave out the 7809 and 7909 if the default output voltage is ok for me?

>>1196107
>>1196172
oh I get it nvm

also

http://www.ebay.com/itm/20pcs-0-1uF-100nF-104-50V-Ceramic-Disc-Capacitors-/332246899669?hash=item4d5b755bd5:g:PiUAAOSwTglYl5hb

are these good ones
I noticed 100uF are almost the same price lol

so if I go
car battery ->
fixed 11 volts ->
isolated power module ->
100nF capacitor FOR BOTH OUTPUTS (or can I use 100uF?) ->
amp

then it should be working?

File: howtoanalogsupply.png (159KB, 1220x920px) Image search: [Google]

159KB, 1220x920px

So i have this evaluation board with an ADC.
The board has connectors for communication and supply. The supply comes in as DVDD, digital supply rail. But theres also an analog supply rail AVDD.

Im using a regulated supply for DVDD. Should i supply AVDD the same way i supply DVDD with a second regulator? What is the best way to fire up this board?

File: Przechwytywanie.png (74KB, 776x805px) Image search: [Google]

74KB, 776x805px

I was listening to music on my stereo and suddenly all sound died. It still works with headphones, but speakers remain silent.
I found datasheed:
https://data2.manualslib.com/pdf3/70/6995/699434-philips/mcm722.pdf?2e8852c5c2fe178c2a91e9835c9ab69e&take=binary

and discovered that most voltages near power stage on page 69 are incorrect and 17V supply is actually at 19V. Should I replace both AN7591 parts? I also wrote down some other suspicious measures from this page - pic related. Please help me, I have no idea how these things work.

File: power stage.png (100KB, 815x612px) Image search: [Google]

100KB, 815x612px

>>1196197
power stage

>>1196190
>Should i supply AVDD the same way i supply DVDD with a second regulator?
That would be a straightforward way to get the best performance out of it.
If the idea of using two regulators sounds annoying, you can also feed your clean, regulated power to AVDD and derive DVDD from it using a small filter, for example a 600 ohm ferrite bead.
Sigma-delta converters are quite forgiving for noise, so you can also try connecting AVDD directly to DVDD.

>>1196207
Im making a pcb to piggyback the eval board, ill just make options for what you suggested. Thank you.

File: Putting that robotics degree to good use.webm (3MB, 720x480px) Image search: [Google]

3MB, 720x480px

Hey /ohm/ I need halp deciding on wat handheld multimeter to choose, with price allowing up to about 150 dollars. Been researching for a few days and since I don't know if brands can be trusted, I'm at a loss

The use it would have is everything automotive, so mostly it'll be low voltage, possibly needing accurate mA range (I do intend to get into DIY electronics soon), but I'd appreciate a clamp model or a clamp add-on, for checking the relatively high start-up and battery charging currents

A feature I'd greatly appreciate is duty cycle, as would be a relatively high resistance value (although at the price point I'm looking, it seems to be common already)

Now, the thing is, I can only buy stuff from Amazon since it's a friend who's doing the actual purchase, and while I'd love to just fuck it and get a Brymen, or one of the many other seemingly good options out there, I don't see one available there...unless I actually go for the Greenlee, supposed to be a rebranded Brymen?

Any input on this? Been checking EEVblog's charts, and as many other sources as possible for 3 days already and can't even begin to decide, since I have no experience in purchasing these items/the brands

Does anyone know of any affordable ESR meters? I want one for testing electrolytic capacitors, but I do not really want to spend too much money on one since I will not be using it that much.

Does anyone have any experience with this one, or know of a project that makes a relatively good meter for low cost?

https://www.aliexpress.com/item/ESR-Meter/32619515115.html

I remember watching a tube amp video somewhere where some guy said that new meters have issues with testing really old caps (like the paper ones from the 1950-60s) for some reason, and I would like one that is able to test those, since I have a very early solid state hifi amplifier c.1963 that I would like to attempt to fix.

File: homemade esr meter.png (155KB, 812x675px) Image search: [Google]

155KB, 812x675px

>>1196259

File: Cout.png (19KB, 312x220px) Image search: [Google]

19KB, 312x220px

>>1196180
As I said, the 100µF caps are already on the amplifier board, you don't need more than that. The 100nF = 0.1µF caps are only for the stability of the voltage regulators and should be close to their IN, OUT and GND pins. The minimum voltage for the converter is specified as 10.8V. If you have 11V that should be ok. It's just enough for the 7809/7909 regulators that have a dropout voltage of about 1.5V at a low current. The idea is that the converter output is not iinitially loaded by the 100µF on the amp board but has already started up when the regulators begin to draw current. As always, RTFM (in this case the f*ing data sheet, see pic).

Important: 7809 and 7909 have a different pinouts. 7809 has IN-GND-OUT while the 7909 has GND-IN-OUT.

>>1196026

it appears the protection circuit (Super-G Switches) is reducing power to the output amplifiers for some reason. most likely cause is that there's some defect in the unit. the other, more hopeful, possibility is that there's a short in your speaker wires, or the impedance is too low, or the temperature in your room is too hot. all these can be tested for and fixed. otherwise, you're kinda screwed.

>>1196263
I just wanted to know if that one would be good enough to tell me if capacitors are dead or not without having to desolder them. I was hoping that someone either got one, or made one from a design online that is a better value.

>>1196430
You typically need to desolder them anyway due to other stuff in the circuit.

>>1196172
>amperage

>>1196583

hehe, apparently some diy'ers get triggered by words as easily as the most sensitive nutjob social justice warriors.

>tfw you gotta come up with a topic for your master's thesis
Any ideas? I want to do something in robotics, possibly with technologies like CNN or blockchain (swarm robots) so I can learn more about them. Trouble is, I don't know how to put those together to come up with a meaningful research question. Should I just read scientific articles like on IEEE until I come up with an interesting idea?

>>1196586

you've been hiding under a rock?
- virtual reality
- augmented reality
- machine learning
- self-driving cars
- voice recognition
- drones

investors are throwing millions at any person or group who has the slightest idea of what they're doing in these fields. you wanna be a billionaire before you're 30? those are the key fields.

can I sample the signal from an audio card or pc microphone with single ended ADC?

>>1196613

of course, just use an op-amp to bias the zero-signal to half-supply voltage. an LM386 in the standard configuration will do that for you pretty much automatically; no need for calculators.

uhh was >>1196592 meant for >>1196588?

>>1196624

yeah

>>1196592
>>1196629
Ok what about those things though? I can't just write a thesis about "Machine learning". I'm not asking people to come up with a topic for me, just some pointers (with a bit more detail than just general concepts)

>>1196632

these are fields with piles of unsolved problems just waiting for some grad student to come along and chip away at the pile. if you have no specific topic of interest, your adviser will have a long list to choose from.

File: 2.png (11KB, 291x252px) Image search: [Google]

11KB, 291x252px

>>1196619
ok, thanks. But what is the bypass pin for? Also I thought that DC components were bad for the typical speaker, is this the reason they put an high pass filter on the output in this example from the datasheet?

>>1196637

the bypass pin improves performance in terms of keeping power supply noise out of the output signal.

of course DC is bad for speakers, so the 250uF eliminates it. but for an ADC, you dont want to eliminate the DC offset, as that's what lets you use a single-ended ADC. so no cap is used. as for the 10 ohms and .05uF, these are for eliminating high-frequency noise so they stay.

>>1196640
ok, thank you.

If I am trying to make a small camera that I can access the feed from like my laptop or phone. Can I get a small just barebones camera to hook up to some sort of wifi module and a micro controller? And is that how I would want to handle this build?

File: IMG_20170620_181307.jpg (3MB, 2336x4160px) Image search: [Google]

3MB, 2336x4160px

What is this small transformer fucker called and where can i buy it?

I have a refrigerator that just frozen's things, does it have a fix?

>>1196739
Turn down the thermostat

>>1196740
It's broken, the fridge was great until it started doing it out of nowhere.

what is a decent free (or at least not terribly expensive) circuit simulation software?

>>1196754
Circuit Wizard.

>>1196739
>I have a refrigerator that just frozen's things, does it have a fix?

A little more detail may get you better responses.

>my car won't start, what's wrong?

>>1196766
I don't know anything more, it just freezes things, it should be operating at a much higher temperature, it's very old also.

>>1196754
LTSpice is by far my favorite and it's free as fuck. The math behind it is better than other simulators, too.

>>1196767
>I don't know anything more
You don't know what the two controls are set at
You don't know what model it is
You don't know what style it is
(freezer above, freezer below, side-by-side)
You don't have a camera to take a photo.

sorry, I can't help you

>>1196713
What's it come from?

>>1196758
>>1196780
Thanks, will check them out

File: impedance_correction.png (9KB, 300x300px) Image search: [Google]

9KB, 300x300px

>>1196640
>eliminating high-frequency noise
loading a low-ohm output wouldn't help much
it's more about stability (phase margin)
wikipedia boucherot cell

I'm looking for a relay I can kick on by running electricity in it.

I'd like a strong relay, 20 or 30 amps would be nice
I use this currently:
https://www.amazon.com/JBtek-Channel-Relay-Arduino-Raspberry/dp/B00KTELP3I/ref=sr_1_3?ie=UTF8&qid=1498019814&sr=8-3&keywords=8+channel+relay

but for some stuff I need more amps

is this something that would work? I just supply 24VAC to it and it switches?

http://www.ebay.com/itm/OMRON-G7L-2A-BUBJ-CB-AC24-Enclosed-Power-Relay-25A-24VAC-DPST-/331325471069?hash=item4d2489795d:g:67UAAOSwax5YtK0q

>>1196947
Check digikey

>>1196947
https://www.sparkfun.com/products/13015

>>1196948
>Check digikey

https://www.digikey.ca/products/en/relays/power-relays-over-2-amps/188?k=&pkeyword=&pv668=2&pv72=2&pv1410=u40A&FV=ffe000bc&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

a DC relay like the above is better than an AC relay coz it's easier to switch on using transistors.

>>1196954
AC relays work fine on DC unless you need very fast action
It's DC relays that chatter when you try to feed them AC
AC relays have a copper turn on them to hold the arm until the next half-cycle.

>>1196959
You better be sure that the contacts don't arc on DC. AC has zero-crossing which kills the arc, but DC can sustain it. Better not be switching upwards of a few (dozen?) amps through an AC relay.

File: 1442986643964.jpg (35KB, 636x476px) Image search: [Google]

35KB, 636x476px

>Graduated with a degree in electrical engineering last year
>Applying for jobs for the last 12 months straight
>10 or so interviews so far (no offers)
>No one seems to give a shit about the projects I did in school (my crowning achievement being a 2DOF robotic arm)
>Every follow up I ask where I need to improve and am greeted with "do personal projects"

So what am I supposed to design in my garage that will make an employer go "wow, I definitely want to hire this sperg with no work experience because of this personal project of his". Everything I look up is either not at all interesting or too simple that I feel wouldn't warrant any interest from an employer. I've been gunning for a pcb design job since that's what I'm most interested in, so naturally I think I should make a pcb from scratch that will do something neat.

Before you shit on me about internships and coop; no I didn't do them in school, yes I regret not doing them. Internships are not an option at this point as far as I know. Yes I've also tried networking, no one wants to be my friend and put a word in for me.

File: 1398110296464.jpg (52KB, 960x760px) Image search: [Google]

52KB, 960x760px

>>1193477
Are you me?

File: ten amps to several hundred amps.png (228KB, 728x663px) Image search: [Google]

228KB, 728x663px

>>1196995
>contacts
The difference in AC vs DC relays is the coil, not the contacts.
AC relays (with AC coil) can be used to switch DC through the contacts.
DC relays (with DC coil) can be used to switch AC through the contacts.
>>1196995
>AC has zero-crossing which kills the arc, but DC can sustain it.
Contacts arc more on opening than on closing.
R/C filters are available to suppress arcing whether switching AC or DC.
>>1196995
>Better not be switching upwards of a few (dozen?) amps through an AC relay.
really? you should get out more.

>>1197080
>The difference in AC vs DC relays is the coil, not the contacts.
wtf?

>>1197093

dont be obtuse, nigger. it's a simple concept: when you buy a relay you can choose either an AC or DC coil.

>>1197067
maybe you should focus your personal projects according to the latest skill trends required by employers

>>1197100
With regards to pcb design, I mostly just see
>Experience using some pcb cad program (altium, pads, orcad, eagle, etc)
>Knowledge in analog, rf or power electronics circuit design
>Can mitigate for EMI

Can anyone give me a quick rundown on relays, I'm going to be swapping doors onto my truck from a later year model with power everything and I'll be building the harness myself to power it.

File: schemeit-project (1).png (9KB, 405x222px) Image search: [Google]

9KB, 405x222px

would this work for an ignition system? ls1 is a magnetic pickup that makes a voltage when a magnet passes by and s1 is the kill switch (closed when running).

>>1197140
>would this work
No, D1 prevents Q1 from switching off.

>>1197145
the diode is because i believe the pickups generate an ac voltage and they only fire when the magnet attached to the crank flys by, its not a constant output source

File: schemeit-project (1).png (22KB, 554x474px) Image search: [Google]

22KB, 554x474px

>>1197140
updated version with 2 setups because it would be for a 2 cylinder. ls1 changed to m1 to represent both pickups.

>>1197147
He's still right.
Also, ignition coils produce (much stronger) spark when the current is interrupted. You might need to shape the pickup coil signal somehow.

>>1197156
ok what if i make it so that the coils are constantly powered and the mosfets cut their power when the pickup fires?

>>1197159
You can't have just a diode facing the MOSFET's gate like that. Maybe a schottky diode would work with its high leakage current, but I wouldn't try it.

A resistor to ground after the diode would be a better bet for discharging the gate capacitance.

Bought a wireless arcade stick that's missing the USB adapter, so I'm wiring the buttons to an old PS3 controller. Can I replace the battery that was in the controller (3.7v li-ion, 610 mAh) with an 18650 I have lying around. Think I'll run into any trouble?

I've found this nice list of 8051 Instructions.
https://www.win.tue.nl/~aeb/comp/8051/set8051.html
Now I'm seraching for something similar and don't quite know what it's called.
Basicly I'm looking for a list of codes that won't be part of the program but sitll affect the way it is assembled. Examples I know are CSEG and ORG. If you know a name for those codes that micht help me already.

>>1197207
Directives (and also operators and predefined symbols). They depend on the actual assembler you're using, so check its manual instead.

Whats a nice opamp for working with ~10MHz signals? Preferably THT but non-tiny SMD is fine too.

File: ignition.png (14KB, 355x325px) Image search: [Google]

14KB, 355x325px

>>1197156
>(much stronger) spark when the current is interrupted
I'd say it only sparks when the current is interrupted.

Ignition in a nutshell:

Contact closes, current ramps up, coil collects energy. Then the contact opens and the stored energy is released but has nowhere to go. Tension rises until a spark forms and creates a conductive path (ionized air) that the energy can follow and dissipate. Next cycle.

The effect is greatly magnified by the number-of-turns ratio of the secondary winding to that of the (switched) primary coil (as in any transformer). The function of the Tesla coil is based on this: a few primary turns and many, many secondary turns - sparks all around.

>>1197258
Those aren't usually everyday things so you'd do better by choosing them on per-project basis.
That said, maybe MAX4213 would be worth considering. It uses current feedback, though.

I want to make a midi controller any advice? Never done a keyboard or midi project before. I just want someone where I can flip switches or press buttons to send midi signals

>>1197258
Look for video opamps, like MAX477.

>>1197258
Check Digikey for through-hole op-amps with gain-bandwidth products above your desired spec.

Most ICs are functionally the same if they meet your minimum specs.

>>1197080
I meant to not switch a bunch of DC current through an AC relay, at least less than around half the AC current rating. Proper high-current high-voltage breakers have an arc-breaking switch that forces a dielectric between the contacts after separating them to prevent a sustained arc.

what is the most common way D flip flop gates (or any other FFs/memory) implemented at the chemical/physical level?

File: flip-flop.gif (4KB, 412x294px) Image search: [Google]

4KB, 412x294px

>>1197416

transistors. 99.99% of chips are just a bunch of transistors connected together. they even use transistors as diodes, and as resistors.

you can thank Mr Shockley for all the teenage boobs you would otherwise never have seen.

>>1197419

I'm aware, but how does the bistable behavior emerge and from the properties of which materials?

>>1197423

has nothing to do with the properties of the materials, but rather with the skillful design of transistor switches. something along the lines of ''a high input turns on a transistor, which turns off another, which is in series with a third, which can only be activated by a low on a second input, which then flips the second off, etc"

>>1197423
A D-flipflop is made from an RS NOR latch with an AND gate powering both the SET line and inverted powering the RESET line. Its inputs are the edge-triggered CLK input at one input, and the D input at the other, so that when CLK is pulsed, the latch sets or resets depending on the value of the D input.

You can look at wikipedia for how logic gates (mostly NANDs or NORs) are constructed from BJTs or FETs, and for how BJTs and FETs work, and for how PN junctions function. Physically they don't make a bunch of seperate transistors, rather they fuse them all together in the same slice of solid silicon.

Trying to understand the "bistability" of a composite logic gate at a silicon level without first understanding how the logic gates and transistors and P-N junctions work is like trying to understand general relativity without first understanding newtonian mechanics.

>>1191510
I have a swapped car with another fan
how do I get it turn on at a certain temp? getting tired of flicking a switch
not sure if this is the correct thread 2bh lads

File: air-conditioning thermostat.jpg (249KB, 800x800px) Image search: [Google]

249KB, 800x800px

>>1197432

an adjustable thermostat. they come in 2 kinds, heating and cooling, but your post doesnt make it clear which one you want.

File: temperature fan control.png (5KB, 640x400px) Image search: [Google]

5KB, 640x400px

>>1197432
Find yourself a fairly sensitive thermistor, and make a voltage divider with it, as pic related. When the voltage from the centre of this divider reaches higher than the voltage set by you using the potentiometer, the comparator will switch off and stop powering the relay (it might be a good idea to put this through a power transistor so you don't pull too much current through the comparator). There are both positive and negative temperature-coefficient thermistors, so your circuit could be turning the fan on when you want it to turn off, in which case you'll want to swap the thermistor divider around so the constant resistor is at the top, or just flip the comparator's two inputs around.

>>1197431
>>1197430

http://www.homemade-circuits.com/2011/12/simple-and-useful-transistor-latch.html

so the "state" in a simple latch seems to come from feedback voltage between the NOR gate with high output inputting to the other with low output

how that feedback works between the collectors and bases of those transistors is still, Physic-ally speaking, magic to me

>>1197443
>>1197441
thanks lads
I found some aftermarket fan controllers online but nobody ships to iceland

File: Thermostat_Honeywell537-DFs.jpg (15KB, 557x542px) Image search: [Google]

15KB, 557x542px

>>1197453

if looks arent important, it's possible to re-purpose thermostats from old analog AC units you find on the street, or old analog heating thermostats (since a lot of people pull those off to switch to digital).

>>1197454
>AC units
we dont have those
http://www.ebay.com/itm/Aeroline-Capillary-Thermostat-Cooling-Radiator-Fan-Control-Switch-UNIVERSAL-/151054632193?hash=item232b8ec501:g:c8gAAOSwg3FUpsPR

Won't this be good?

>>1197432
>I have a swapped car with another fan
>>1197441
>File: air-conditioning thermostat.jpg
>>1197454
>File: Thermostat_Honeywell537-DFs.jpg

>car fan control operates at ~200F
>suggests 45F-90F as alternative

>>1197513
Uh?

>>1192205
>Another thought to improve prototyping: Is there some way of loading a spice file (or other circuit simulation file) onto a microcontroller and having it behave as the components modelled in the spice file would?

I don't build HIL stuff, I find it interesting though. These are just my two cents after a bit of thinking, keep that in mind.

What you're referring to is called a HIL (Hardware in the Loop) simulator.
Depending on how broad you want to be you would need peripherals accordingly. Most HIL systems usually simulate something more complex like a break system or a motor and have circuits specific for the job.

To simulate a BJT for example you would either need to build an equivalent circuit out of.. well, BJTs, OPAMPs, etc. and tune that with the MCU or have your MCU sample input voltage/current and then tune a voltage/current source/sink, etc. accordingly. However this makes response dependent on sampling frequency and that would mean either slow response or you would need a fast system for example an RPI, where there could be problems with real-time, I don't know how RT is the RT kernel, or an FPGA. Still there would be limitations. Configuring an external circuit using an MCU would be a better approach.

From a signals and systems standpoint your simulator would need to be much faster (10x) than the system using it to appear "genuine" in most cases.

Btw, take a look at the STM32 MCUs. There are cheap boards from China. FPGAs can also be found on aliexpress for around $20.

It would be easier to simulate a custom logic chip using an MCU, but that's exactly what you can do with an FPGA.

>>1197518
Fuck, what the fuck did I do with the a/an stuff? Eh never mind I'm tired. Sorry for the typos.javascript:;

>>1197258
Depends on the gain you want. 40 dB gain @ 10 MHz means a GBW of 1 GHz. For that you're looking at differential op-amps, mainly used as ADC input buffers.

>>1197067
You might have to look for non-design jobs. These days employers want MS and up for design. Widen your horizons.

>>1197543
I haven't seen any employers looking for masters graduates. I'm not trying to work at google or some huge company, I'm fully willing to work at a startup.

What "non-design" jobs are you even referring to by the way? I've tried looking into technologist positions if that's what you mean?

>>1197518
Sounds somewhat promising. I was just thinking of using it to simulate audio frequency or lower, so a standard microcontroller's MHz clock would probably be enough to simulate pretty much anything.

>>1197554
By non-design I mean test, QA, manufacturing, that sort of thing.

>>1197567
I've applied for those positions as well and have gotten a few interviews, but no offers there either. The interviews I've mostly got were for design positions.

I can get 2 buck converters to supply 6 amps for $11 each, or I can get one buck converted that supplies 6 amps for $68. In general terms, how much efficiency would I really gain by using a more expensive alternative?

So I'm going through the 100 circuits in Getting Started in Electronics Forrest Mims III .
How do I understand how the circuits work?

>>1197610
S P I C E
P
I
C
E

File: Hantek_6022be_pcb_top.jpg (1MB, 2592x1944px) Image search: [Google]

1MB, 2592x1944px

So I need a cheap oscilloscope (and I really mean cheap), so I was looking at some usb oscilloscopes.

According to some reviews, the cheapest (~60 eur) which is not completely just a toy is the Hantek 6022BE; now, I'm don't know much about oscilloscopes or analog electronics in general, but looking at the specs and pcb (pic) on sigrok's website I realized it's basically a 8-bit dual channel adc (AD9288) directly connected to a usb controller (I suppose this explain the really bad acquisition rate at lower time div), and that's basically all.

So I was wondering if maybe it was the case to "invest" in some other usb based oscilloscope, maybe fpga based with a little of internal ram, such as Hantek DSO-2090 (https://sigrok.org/wiki/Hantek_DSO-2090). Would it be just a bigger waste of money?

Someome love me

>>1197564
Audio? Well, that's 20kHz tops which means a sampling freq of 40kHz. Yeah, you should definitely look into that.

>>1197626
If you're willing to pay $60, consider a used real scope.

>>1191510
I got a stupid question regarding multi-meters.

is there any damage or wear on inside components when measuring voltage on a circuit that has 200A flowing? note: IN VOLT MODE not in amp mode.

Just wondering because my circuit shorted accidentally and my brand new expensive DMM was measuring voltage at the time. 200A for 1 sec sounds like a huge amount of current for a multimeter to deal with.

>>1197626

If you do buy a USB scope, make damn sure you understand the risk involved. When I considered buying one I was scared away by the tales of people blowing up their $1000 laptop.

Like that other guy said, a decent used one is a good idea, or just save up $400 and buy a Rigol. That's what I did, and I love it.

If you want to learn about electronics, you have to own an oscilloscope. Some people say that your first big investment should be a logic analyzer, and they may be right depending on what you are working with.

Another great tool for electronics work is a function generator. The MHS-5200A is a nice starter for about $60.

>>1197674
>my brand new expensive DMM was measuring voltage

A voltmeter has very high input impedance, which means that current simply does not flow through it unless the voltage is tremendous. The amount of amps flowing cannot affect the voltmeter unless you short something out and create an arc welder that destroys the meter and you.

>>1197696
Looked up my DMM manual, input impedance is 10M at the minimum so at 600v its only 36mW (ohms law). I feel dumb for my original question now lol.

>>1197608
If you're hoping to parallel the output of cheap buck converters to get more current, that won't really work.

>>1194160
I know the post's a week old, but if you want to make it into a clock, why not cut out the two segments needed to make a one in front of the first digit and leave it at that? You have enough space for it, unless you absolutely need a 24hr clock.

File: 51141da0ce395fe67e000005.jpg (27KB, 400x367px) Image search: [Google]

27KB, 400x367px

I'm connecting a 4 pin molex to this barrel connector. Should I connect a ground wire to the detection pin or will very bad things happen?

File: dc5v2a.png (33KB, 856x479px) Image search: [Google]

33KB, 856x479px

>>1197981
>Should I connect a ground wire to the detection pin or will very bad things happen?

The detection pin is connected to the sleeve when no plug is inserted.
What happens if you connect it to ground wire depends on how the device you're connecting it to is wired.

File: SOT25_gnd-via_cooling.png (163KB, 1420x836px) Image search: [Google]

163KB, 1420x836px

Any tips for SOT25 heat dissipation?
Currently using layout like in picture (sot25 ldo voltage regulator), maximum power dissipation is 250mW in datasheet, might go up to 400mW in application for very short periods (every few seconds up to 5-10ms) so wondering if it will be adequate

Also, any book recommendations solely for pcb design? A lot of my designs would be barely acceptable for anything

File: example.png (8KB, 251x128px) Image search: [Google]

8KB, 251x128px

>>1198102
LP2985-N datasheet has some info on thermal considerations. They don't specify max. dissipation in favor of thermal resistance and how to estimate the influence of the layout.

I need to replace a coil in a mechanical relay that takes 240v. How can I find one? I can't figure out how to search for it and not find 12v relays for switching 240v supplies

>>1198171

digikey lets you specify a particular spec or group of specs, and then only shows those items which match.

the following search, for example, is for any relay with a 240Vac coil.

https://www.digikey.ca/products/en/relays/power-relays-over-2-amps/188?k=ac+relay&k=&pkeyword=ac+relay&pv72=32&FV=ffe000bc&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

(generally, replacing a coil in a relay is likely to result in a hopelessly broken relay. better to replace it)

File: 240v ac coil relay.png (167KB, 744x306px) Image search: [Google]

167KB, 744x306px

>>1198171
search string filename
www.aliexpress.com/popular/relay-coil-240v.html

NEED A NEW THREAD - its not doing the jump-to-the-top-of-the-page thing.

>>1197695
What do you think of Hantek? They had some DSO whatever 100MHz oscilloscopes which you could hack to double it.

File: last.png (16KB, 187x152px) Image search: [Google]

16KB, 187x152px

>>1198198
ohm is too heavy
activate buoyancy

File: bottom-off.jpg (364KB, 1296x968px) Image search: [Google]

364KB, 1296x968px

>>1198194

I'd love to replace the whole assembly but it's part of a turntable, so the relay is completely integrated in this little module.

If replacing the coil doesn't work I'll try figuring out some other workaround, ultimately I just have to move a piece of light plastic about 3 degrees so I'm sure there's something I could do that would be small enough to fit.

File: 1479766348080.jpg (143KB, 1615x998px) Image search: [Google]

143KB, 1615x998px

I've been using this Raspberry Pi powered lapdock for about a month and it's working great, Then out of the blue after turning it on, nothing happens. Pressing the button on the lapdock does nothing, when normally it should reveal it's battery level. I notice the distinct smell of magic smoke. I think I just fried it.

Not sure how it happened but I think it's because power backflows through the USB ports that's used to connect the keyboard/mouse to the Pi. I think it overloaded it somehow when the Pi tried to draw too much power. How do I go about diagnosing the broken component and replacing it?

File: burnt lapdock.jpg (2MB, 3024x4032px) Image search: [Google]

2MB, 3024x4032px

>>1198302
opened it up and found the burnt parts

I have no idea what they are as any markings they once had is now melted off. Is it possible to fix this?

>>1198198
>NEED A NEW THREAD -

>>1198346

>>1198249

it's probably not helpful but that thing looks more like a solenoid than a relay. they're similar, but the purpose of a solenoid is to cause linear physical movement whereas a relay closes/opens electrical contacts.

>>1191510
Hey guys a friend of mine gave me a RC car to mess with, and I am wanting to attach rpi to it and control it via WiFi, and I already did this with one RC car, with help of a blog and explaining the pinouts,

Anyways, I googled the info on the chip, and on the board, with no results or I just didn't look at the right place

>on board, "YX-118R"
>on chip, YX RX-978S" and underneath it, it also has "4423"

If all else fails I can just hook the wires from the motor directly to the gpio holes/pins/whatever on the raspberry pi zero w, also with it using 5 AA batteries, can I also power rpi, and rpi pulls the voltage it needs? maybe just put 4 in to run at 5 volts instead.

>>1193030
Yes in a general it maters as application must always be considered. The following is an example from wikipedia:

Some types of capacitors, primarily tantalum and aluminum electrolytic capacitors, as well as some film capacitors have a specified rating value for maximum ripple current.

Tantalum electrolytic capacitors with solid manganese dioxide electrolyte are limited by ripple current and generally have the highest ESR ratings in the capacitor family. Exceeding their ripple limits can lead to shorts and burning parts. (is fire a problem in your application?)
Aluminum electrolytic capacitors, the most common type of electrolytic, suffer a shortening of life expectancy at higher ripple currents. If ripple current exceeds the rated value of the capacitor, it tends to result in explosive failure.
(does the device have a service life of X number of years?)
Ceramic capacitors generally have no ripple current limitation and have some of the lowest ESR ratings.
Film capacitors have very low ESR ratings but exceeding rated ripple current may cause degradation failures.

Wikipedia is not a bad place to start your research into electronic components.