/ohm/ - just in time edition

>>1087810
How to look like a super l337 hacker in 3 easy steps
Step 1. buy an analog oscilloscope
Step 2. buy a logic/spectrum analyzer
Step 3. turn both on, then turn the lights in your room off

>>1087818
step 4. make a useless led cube

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Doesn't anyone remember this company?

They were selling a neural network ASIC called the CM1K. It was a computer with no instruction set. Also they had a very interesting feature where they could be daisy chained together as long as you wanted.

I bought a usb devkit they were selling on digikey months ago because it was also very cool but they never shipped it. On digikey only one order backlogged (mine). Can't find any hobbyists on the internet who ever had one.

Should I go to trade school to become an electronics technician?

Aside from the obvious non-contact amperage readings, are there any features that a clamp meter can do that a normal DMM can't? I'm looking to pick up a <$50 cheapo just to take some quick measurements on my woodworking tools, and so far I've only been looking for autoranging, min/max, and inrush as far as features go, but if there's something else they can do, I might as well see if I can get the extra features in my price range.

>>1087820
step 5: Buy a ridiculous RGB LED matrix and throw them on your wall and program them to glitter green down like the matrix

Does anyone have a quick and safe way to open laptop batteries to harvest the juicy 18650's inside? Currently using a hammer, knife, flathead screwdriver and a lot of yelling.

>>1087884
Hair drier to soften the glue, guitar pic for separating the plastics and pressing the clips holding it together
There are kits online for opening phones that have plastic pry bars perfect for salvaging parts

>>1087825
Hey thanks, that makes sense. It's that kind of "open U"-current meter, so I assume I need to disassemble it to find out.

Anyone have experience fixing Fluke shit? I can't afford sending it back for the repair price if that is close to new price. Understand why I got it for free now

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So last time I used multisim I'm pretty sure it was a single digit version number, and I wasn't very deep into my double digits myself. Back then, I used to load bits into the word gen and dump serial/parallel "words" into small circuits like pic related, to simulate for example the data required to drive a PISO, send an i2c packet, or to trigger a change on a 74HC595. As I couldn't simulate the uC, I figured I could at least simulate the data I'm expecting it to send and receive so I can test that my periphery logic works as expected. I could generate all my clocks and a sample byte of data to make a bunch of LEDs jump in 10 lines, and it seemed to get me by.

Am I doing it wrong?

Bonus question; Has multisims "auto track layout" thing always been this shit or am I colouring its abilities with nostalgia? Muh autism demands much cleaner layouts than this, but (readability aside) does it really matter at this level?

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Has anyone here used one of the many MS2108 rebrands? It seems too good to be true for a true-RMS clamp meter with inrush, but if it actually works, why the fuck not?

>>1087881
>non-contact amperage readings
That's precisely the only reason why clamp meters were created. Can you imagine how chunky, expensive, dangerous and inconvenient a DMM for measuring at the 100s amps scales would be?
In general DMM can only handle 10~20A max.

>>1087893

ah, didnt realize it was a clamp meter (without the clamp), so the dead fuse idea is no longer appropriate. so, the odds of it being an easy 5-minute fix had dropped considerably.

Do you guys take apart electronics stuff to learn? Saw an offer for 10 old broken game boys for very cheap and was wondering if it'd be worth buying

>>1088005
i made make simple things to learn. esp pertaining to op amps and transistors

>>1088005
At the very least you could use the case.

>>1088005
I don't think you would end up learning a lot from such an integrated board, to be honest.
I think things like >>1088020 are a better alternative.

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SSD1306
blackberry keyboard
Esp12E

Going for it. Keyboard will be the hardest part because of the custom connector. In the meantime does anyone know wtf is wrong with my oled? Only a tiny sliver of the display near the top works.

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>>1087810
I was messing around with a piezo pickup/contact microphone for acoustic instruments, took it apart and what I found were these simple 30cent piezo elements glued in a plastic case.
I want to use this for my cello and maybe a classical guitar.
Can I just put one of these under a foot of my cellos bridge? I saw that the piezo material itself is very brittle, and the foot of a cello is slightly concave to fit on the convex top of the cello. Would the piezo element just be bent and break? Would it withstand the pressure in the first place? Not sure how that is done with professional pickups.
And where would I put it on a classical guitar? Just taping it to the top didn't work with the one I bought, but when I pressed down on it it sounded pretty nice.

>>1088066
get this to run linux and /g/ will want a thousand

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Could someone help me with a circuit?
I am asked to study this schematic and knowing that Vin do a sweep from 0 to 5 and talk about what it can be used for.

I have already analyzed the circuit, and I think is something like a smith trigger done with mosfet, but I don't know what the feedback is used for, maybe extra current, or stability? I am not experienced implementing digital circuits.

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>>1088145
Adding extra info, if you simplify knowing that they are typical nmos inververts, you get something like this

>>1088143
bonus points: secretly turn them into a botnet
>>1088066
at best the screen is being fed the wrong location for where to display your picture, and at worst there's a matrixing problem
That keyboard's gonna be a bitch. What's the output look like?

>>1087810
Not sure if this is okay, but I might as well ask here.
I'm currently stuck on a project for college, but that project is the basis for my diploma basically.
I'm programming atmel uC's with an AVR dragon programmer and codevision. I can read and program my atmega 168 without any issues, but my atmega 164pv just won't even connect with the programmer. I could read it once or twice but that seemed to be random since a minute later he just couldn't connect to it anymore without me changing anything. I have 2 of the uC's and tested them both, no luck but that also shows me that it's very unlikely a faulty chip.
I checked and re-checked the correct pins, it should work, the cables are also not faulty since the thing works with the 168.

I just get a generic error message that says "check hardware connections, security bit, etc." when trying to interact with the chip.
It's on a breadboard right now, and I was thinking that the larger 40-pin chip maybe doesn't connect properly on there? I have no clue what to do anymore.

>>1088148
That's essentially an SR latch, assuming the dot in the middle serves the function of an OR gate. The circuit only serves a function if Vin starts off at +5VDC and then cuts off, at which point Vout will be at 0VDC. Even if Vin returns to +5VDC, Vout will remain at 0 because of the feedback loop.

I'd say it would be something to put on a fridge circuitry to tell you if there was a power cut while you weren't at home so you'd know to check that your meat hasn't gone bad, but who knows. There's no way to reset the latch, so it certainly has limited use and comes with the rather difficult task of initial activation.

But that's all assuming Vin is at +5VDC or 0VDC, and I have no experience in how FETs behave under partial power.

Need any info on antenna design. I know jack shit about RF.

Also, on a related note is there a cheap way to build a mm-wave antenna that does not involve stripline? (Will also take any info on how to design distributed elements and how to lay them out properly on a PCB) Only needs to receive, not transmit but I've never worked with such high frequencies before and I don't know what traps I need to look out for.

>>1088140
I don't know about cellos and contact microphones, but yeah, the actual element of those piezo disks is made of thin ceramic and it cracks easily when you bend it. That doesn't necessarily kill it entirely and immediately, but still.

>>1087821
I think I saw that on Digikey but it honestly didn't seem very useful.

>>1088005
I am an EE, I took apart / take apart all sorts of shit. But generally what you learn is more about product design than electronics, since most of the crap one picks up is consumer electronics. Old HP gear, on the other hand...

>>1088317
You're going to have to be more specific. Otherwise it's
>Pozar
>Ramo, Whinnery, and Van Duzer
>ARRL Antenna Handbook
>buy CST license

>>1088145
https://en.wikipedia.org/wiki/Bus-holder

>>1088317
Microstrip is used exactly to keep things cheap and simple.
Find a microstrip antenna design for your band and implement it as is, without substituting materials etc.?

>>1088348
Okay, thanks for the info. I suppose I'd have to cast it into some resin or something that withstands the pressure and just transfers the vibrations. Too much effort probably.

>>1088284

>>1088351

Thanks, will read into that and investigate about it.

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>>1087810
Does /diy/ have recommendations for a "all-in-one" station? I currently have a Aoyue 937 at home which is great but it's just a soldering iron. Last year I've practically learned how to make PCB's myself and actually solder SMD but I used tools at school to do so(manual pick and place machine, professional oven)

I'm currently eyeing pic related(Aoyue 2703a+) but it's 300+ euro.

if anyone is interested in homemade stuff, i just made a video about homemade foil capacitors
https://www.youtube.com/watch?v=7vntVIb3lg8
worth a watch i say

>trying to remove an IC from a board
>Cutters to blunt to cut off the legs
>getting frustrated using wick+desoldering pump
>decided to use heat gun
>on for about a minute very close to the chip
trying to melt the solder that's stuck to the leads
>turn it off
>shit is smoking
>fug
>surrounding chips are hot to the touch
>still couldn't remove that i needed too chip anyway
>later saw that 2 nearby electrolytic caps had bulged, which i believe may have caused the smoke
>test points have burn marks

How much heat can plastic IC's take?
none of the solder melted so im hoping that none of them got hot enough to fuck the chips entirely, and these arent common IC's either which is a huge pain in the ass if i need replacements.
tldr reassure me that i havent fucked up :)

>>1088005
The way i've learned about electronics has mostly been through looking through old service manuals and schematics for amplifiers or synths or whatever, or just attempting to repair something and learning through that

>>1088428
Test it and if it doesn't work, you probably fucked up. If it works, but stops working soon, you probably fucked up.

>caps had bulged
>burn marks
Scratch that, you fucked up. Maybe just not too much.

Just how hard would it be to make something that detects the direction of a noise

would it be as simple as measuring the delay between two mics with ADCs

if I used an FPGA would it be fast enough?

>>1088509

For the general case you need 3 mics for a 2D plane, 4 in 3D, but as long as the sound source is far away relative to the distance between the mics you can determine the direction from 2 yes.

Sound data streams are small, you can do this on a microcontroller.

>>1088005
If you're looking for parts, you prolly won't get many out of those

>>1088509
The hard part is the feature detection, i.e. determining that a sound on one microphone at t1 is the same sound as on the other microphone at t2.

Provided that you can do that, it's just a matter of solving equations. Given two points in the plane P1 and P2, The set of all points P where |P-P1|-|P-P2]=k is a hyperbola. In 3D, that gives you a hyperboloid; you need to add a third microphone to determine the angle about the line joining the two microphones (i.e. the elevation if the microphones are at the same height, the azimuth (heading) if they're one above the other).

If the sound is far from the microphones relative to the distance between them, the hyperbola can be approximated by its asymptotes (i.e. the difference in distance is just the distance between microphones times the sine of the angle).

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/ohm/,
I purchased an arduino when radio shack was kill. How do I turn it into a robot servant?

>>1088548
get a cheap ac drill and a triac speed controller off ebay

drill a hole in the base of a dildo and hot glue it in place

get an arduino compatible voice recognition shield that does "on" and "off" and use that to control the dildo

Anyone know of any /ohm/ related black Friday sales online? I'm not looking for anything specifically, just don't want to miss sales.

>>1088428
>How much heat can plastic IC's take?
It depends on the part. Some are rated for very high temperatures in military or industrial applications. You'd have to read the datasheet.

>>1088657

> black friday

that's just hype made to take your money. It's one of the most cancerous things on the planet.

Especially for electronics tools, you ought to just not be cheap when you need something. Otherwise, just don't bother.

>>1088575
I decided to do it myself .I have the rumble motors of my 360 controller. I need to fabricate a dildo.

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How do I use this ST viper37 as a simple non isolated buck converter? The lower powered models all have examples for non-isolated circuit but not this model. I'm not familiar with optocoupler feedback configurations like this. I need the bigger mosfet on this model so smaller models like he viper06 are no good.
http://www.st.com/content/st_com/en/products/power-management/ac-dc-converters/high-voltage-converters/viperplus/viper37.html

>>1088799
> How do I use this ST viper37 as a simple non isolated buck converter?
You don't. It's designed for use in flyback converters. The FET source is hard-wired to ground.

If you want a high-current buck converter, use an appropriate IC with an external p-channel FET.

Apart from anything else, Rds[on]=4.5 ohms is far too high for a buck converter (but not a problem for an offline switcher where the primary is a few hundred volts but low current).

So it's clear to me what 2/3-way solenoid valves do.
But what the hell does a one way solenoid valve?

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>>1088898
>You don't. It's designed for use in flyback converters. The FET source is hard-wired to ground.
>If you want a high-current buck converter, use an appropriate IC with an external p-channel FET.
>Apart from anything else, Rds[on]=4.5 ohms is far too high for a buck converter (but not a problem for an offline switcher where the primary is a few hundred volts but low current).
They do it with the lower power models, they still have the same topology, I just can't figure out how feedback pin on the viper37 functions in comparison to the viper26.

I just want the viper for high voltage conversion, I will use it to drop to 36V 1A then use secondary converters for low voltage high current rails.

>>1088898

Not the guy who asked the question.

>You don't. It's designed for use in flyback converters. The FET source is hard-wired to ground.

It is on the other vipers too, then again I can make heads nor tails of their buck configuration in their sheet.

>>1088692
>price determines quality
I'll happily pay less for the same shit as everyone else, even if it somehow gives me cancer.

>>1088799
- You could go with an opto even if you used it as a buck regulator. Yes, it's cumbersome and costly, but it's straightforward and it works.
- You could replace the opto's NPN side with a PNP and then use another transistor and that zener/resistor contraption (or just resistors) across the output to drive the PNP's base.
- Or you could just use that flyback regulator as a flyback regulator, which would remove the level shifting problem. In that case an NPN transistor and a zener would handle the (nonisolated) feedback.
- Or you could consider using another flyback regulator, with a more convenient feedback pin. If you drop the requirement for it being a buck regulator, the smaller Viper family regulators can provide much more power.

>>1088901
It's inverted, i.e. increasing output voltage lowers the voltage on the FB pin, switching the converter off.

With an isolated setup, the threshold sensing occurs on the output side. Their circuits use a zener in series with the optocoupler input. Exceeding the zener voltage turns on the optocoupler, lowering the FB pin and switching the converter off.

You could do the same without isolation, just using a zener and resistor into the base of an NPN transistor. It's a bit more complex if you want a stable control loop, i.e. a stable in-range output voltage resulting in stable PWM oscillation. Insufficient gain or too much latency will result in voltage overshoot. Too much gain will result in the circuit alternating between full-on and full-off.

/ohm/ pls help
I'm learning about capacitors and one thing is confusing me. In pic related, according to the book, Vout is Vf+Vc where C is the capacitor. Why is this the case? When C is charging, why does that voltage get added to the output voltage?

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>>1089176
and i fucking forgot to post the picture

>>1089176
>>1089177
pls halp

>>1088899
I'd imagine it just kinda acts like a latch? Got a pn or pic?

>>1088755
The weights on vg controller rumble motors are designed to beat against firm plastic to make it vibrate, so you'd probably need to make a hollow resin -thing you want to make that isn't against board rules at all- and have the motors inside it.

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I want to build a computer, almost from scratch. I want to buy an 8 bit processor, get a few kb of ram, and connect it all to a board of switches and LEDs to do binary I/O like an altair 8800. I don't have a lot of experience with electrical engineering, and I've designed digital logic circuits like an ALU (simple compared to other digital logic circuits) before but never actually made them (no parts). I can find 8080s online, but I can't find memory which I can connect to an 8080. Is there a way to get old memory like this, or am I better off trying to buy a newer processor? I'm trying to stay in the 8 bit family to keep things simple.

>>1089177
That's a basic RC low-pass filter. When the cap is charged, Vout = Vc = Vf

>>1089191
Think I'm looking for "IC memory". I'll have to read more into architecture and digital logic and also figure out what chips are compatible with what microprocessors

>>1089223

what you want is an EEPROM I think

> nobody tell him you can buy a complete computer with 1kb flash for 20 cents

>>1089233
You mean like a single chip computer, right? I've been browsing and found a few (mitsubishi 7480/81 family is one I saw). Can you recommend some more resources like that

>>1089237

when it has the memory and processor on the chip it is called a microcontroller

They also have a lot of other bells and whistles (ADC, PWM, interrupts, watchdogs, even DACs now)

You can buy an LPC810 (which is an ARM) kit for less than 10 bucks from adafruit but that can be confusing since it has no debugger

the obvious choice is buy one of the AVR atmega328p boards, probably the most user friendly is the Atmel Xplained Mini, lots of resources for AVR programming online since the Tarduino is so popular

if you want a good debugger you should consider one of the PICs and a Pickit 3 ripoff, but IMO those are pretty confusing

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>>1089239
Thanks a lot! I'll definitely look into that.

I'm looking at EEPROM memory, and I'm checking out this data sheet and trying to interpret it:

http://www.jameco.com/Jameco/Products/ProdDS/74843.pdf

The chip has 15 address bits but is 256k memory. 256k of memory would require like 18 bits to address. Is each pin a single bit for the address, or how does this work?

>>1089243

I've never worked with an eeprom but it looks like you read/write 1 byte at a time through 8 pins, I/O 0-7. it has 15 memory address pins which suggests that it's 256k bits of memory (not bytes)

my understanding is you put memory address in on one of the 14 pins and select a mode, then wait for it to complete and get a complete signal, then it will output the byte you select on the IO pins. when you write, you do the same but you need to also input the new byte on the IO pins

>>1089251
>256k bits

That makes a lot more sense (2^15 = ~32,000)

I have a pretty rudimentary understanding of memory and CPUs from my computer organization and architecture class, so it looks like I've got a lot more to study before I can actualize any of this stuff. Thanks a lot for your help!

>>1089252
Memories are generally sold based on their size in bits. The number of address lines depends on the actual organization, so that 8b wide memories have 3 address lines less than you'd expect, 32b wide memories 5 less and so on.

>>1089252

looks like a very simple chip to use. you connect the 15 address lines, and 8 data lines directly to the related pins on the CPU. and you're left with only 3 pins you have to deal with.
OE - drive it low to read data out
WE - drive it low to write data in
CE - drive it low to turn on the chip

so to write data, you drive WE and CE low for 1 cycle; to read you drive OE and CE low for one cycle.
as i recall the 8080 has WE and OE outputs so you just connect them there directly.

as for CE, you can connect it to A15 on the CPU. this will select the chip whenever you read or write to an address between 0 and 32767. i dont recall whether the 8080 expects the ROM to be in the low end or high end of the memory map, so you may need to invert A15 first to put it at the top of the memory map.

personally I would avoid the 8080 in favor of the 6800 or 6502 family, coz everything about the 8080 is backwards and weird. my guess is Intel learned about the 6800, and then decided they didnt wanna be sued for copying so they purposely turned/flipped things upside down. so, an instruction to put 12 into the A register is straight-forward on the 6800, LDA #12 - load accumulator A with the number 12, but it becomes twisted in the 8080, MOVI AX,12 - move immediately into AX the number 12.

>>1089206
yes but when the cap is charging Vout = Vc+Vf, i dont understand why this is the case, why isn't it just Vout=Vf?

>>1089404
> when the cap is charging Vout = Vc+Vf
No. Vout=Vc, always. Vout IS Vc; they're just different labels for the same voltage.

The only sum is Vf=Vc+Vr

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Would this work? The idea is you use this to test ethernet cables by running current through them and seeing which LED doesnt light up. if they arent all lit, the cable is bad.

>>1089423
what are you planning to use as current return path? not all cables have shielding.

different idea: use a decimal counter to multiplex the leds. with some diodes you can use inactive wires as return path. if you wire it correctly, it not only shows you continuity, but also whether the wires are in the right order.
i have a schematic for this somewhere, can't find it at the moment though

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>>1089434
the power source is a battery, it still needs a return?

if so, I can just use pins 4,5,7,8 to return it since they arent used in a Cat5e setup.

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>>1089443
>>1089434
found the schematic

>>1089444
would >>1089443 work though? full disclosure, I just picked up a soldering kit today and all I have at my disposal is some christmas lights, female rj45 and a portable battery.

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>>1089447
you're shorting +5V and GND right at the beginning.

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>>1089449
shitty diagram sorry, the cables would be separate. power would go to 1,2,3,6 since those are the ones data flows through. 4,5,7,8 would be the return.

>>1089457
you can do that, yes.

>>1089459
awesome thanks for the input, will show results later on.

>>1089191
In my school, we built simple computer using an Atmel AT89S52, (which is actually a microcontroller but putting a certain pin to ground "forces" it's self to read external memory using 2 of it's ports ), an HY6264 RAM, an AT28C64B EEPROM (both 8-bit 64Kbit memory 13-bit address) and a few other 74xx TTL logic multiplexers, buffers, etc. We also built a "control deck" for our computer where we could write/read 8-bit instructions/data directly to RAM or ROM using a 16-bit address (used the 3 most significant bits for addressing different "modules", 000 for ROM and 111 for RAM, thanks to the TTL multiplexer), RUN/STOP switch and a reset button.

If you guys are interested I can dig up the schematic and post it here.

>>1087810

I have one of these radar guns

http://www.edparadis.com/radar/

How do I detect if it is outputting a 10ghz signal? all I have is a tds360 scope with a 200 mhz bandwidth, so I guess I need to build a receiver.

>>1089578
9.9 MHz oscillator and a modulator.

>>1089578
Spectrum analyzer would be the standard answer, but in this case there's no real need to detect the actual microwave output to see if the microwave side is working. Measure the signal from the detector (well, after preamplifiers) and see whether you get the expected doppler frequency when there's a wheel spinning at a known speed in front of the radar.

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Hey /ohm/, since it's black friday I thought I could finally get started learning some of this electronics stuff before my actual engineering class in the spring. I'm planning on buying a solder and the book by Mims in the recommended section of the OP but I wanna make sure I really have everything. Are there any other useful tools or parts before I get started learning this? Don't have too many electronics stores where I live, and I'd hate to start reading only to realize I can't actually start working on projects.

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just a pic related.

>>1089643
Assorted electronic components kits can be useful, you should buy those from eBay or aliexpress. Just a pile of various resistors, LEDs, some common transistors and capacitors, diodes. Also prototyping boards.
Might be worth getting something like an arduino starter kit, they usually contain some assorted resistors, cables, buzzers, LEDs, some simple displays.

For soldering iron, try to find a cheap Hakko 900M compatible soldering station, they're usually sold around $50. The tips are cheap and very easy to find, again I usually buy from eBay. If you know you're going to be working with electronic circuits, it's well worth buying a station instead of a shitty handheld with inaccurate temperature control. Also a copper sponge from eBay to clean the tip, most cheaper irons don't come with one.

>>1089863
Thanks for the suggestions! I've actually already picked out this starter soldering set. Comes with multiple tips and a stand for something like twenty bucks now. I'll take a look at that hakko though just to see if it's a better deal.

>>1089708
>Remember when HP were good?

Just bought an FPGA (ElbertV2) and I'm going to learn how to program it when it comes in tomorrow. I have a fair amount of experience with analog circuits, and some with digital circuits using ICs, but this will be my first time with an FPGA.

End goal is to make an up / down counter which will feed into another circuit running a convolution algorithm via FFT and the convolution theorem.

What are you working on /ohm/?

>>1090099
finishing my mailbox alert system... the transmitter part is up and running, now its a matter of learning esp8266 and Blynk to get it on my phone

Can I use the voltage on a piezo element to reasonably accurately get the frequency of some sound played right next to the piezo element? I.e: it I play a 2400hz sound wave next to this element, would the output be around 2400hz?

>>1090124
yes

>>1090147
Perfect! I've got an idea for a 300 baud modem using a piezo element and Arduino based on a project I worked on before:

http://www.github.com/collinoswalt/modem

>>1090124
> would the output be around 2400hz?
If the sound source is moving, there'll be a change in frequency due to the Doppler effect.

Inaccuracies in the piezo element will introduce distortion, but they won't change the frequency even slightly.

>>1090189
piezos are fairly accurate. frequency sensitivity is more of an issue.

>>1090189
Since it's a 300 baud telephone modem, it's meant to stay stationary, or at least stationary relative to the piezo. the modem itself could get bumped, but that bumping could add noise. An acceptable issue since this is meant to emulate a real life telephone modem

>>1090190
I know it won't be perfectly accurate. My margin-of-error algorithm tolerates a 50% margin of error (half the samples required to form a complete wave)

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What's a good little display with decent refresh rate and not too high current draw? I'm making a kitchen scale, and I want it to be able to tell me the current measurement with minimal lag. I tried a standard 16x2 LCD, but it's way too slow. I also ordered one of those Nokia 5110 screens on aliexpress, and I will try that when it arrives some time in 2017.

Maybe a simple 7 segment is better?

Which companies make good clamp meters? Right now I'm eyeing UNI-T or Fluke(Half price employee discount friend, woo!), are there any others worth considering? I'm not looking for anything in particular at the moment, I just know I want a clamp meter, and I want to check out my options and see what's out there before deciding.

newb here. Im trying to control a dc motor connected to a battery with a potentiometer and failing hard. I tried googling and stuff but im being a dumbass. Can someone explain how to do this simply? thanks

>>1090450
The resistance of the potentiometer needs to be comparable to that of the motor. If you put a 10k pot in series with a 100-ohm motor, as soon as the wiper moves away from one end, you'll get almost no current.

Second, you need to use the pot as a variable resistor (one end connected to the wiper) rather than as a potentiometer. In order for a potentiometer to work effectively as a voltage divider, its resistance needs to be much less than that of the load.

hey /ohm/, i recently made an approximate differentiator circuit for a class. During the testing we were comparing the input signal to the output signal by measuring the input signal on channel 1 of an oscilloscope and the output signal on channel 2. One of the questions is "why is it preferable to invert channel 2" and im drawing a blank. Anyone have any ideas why you'd want to invert the output?

>spend hundreds on components and measurement gear
>did a few projects
>learnt a few things
>starting to get bored of it all now

Anyone else experiencing burn out?

>>1088066
>>1088143
install gentoo

>>1090475
pls halp

>>1090475
out = - d(in)/dt

usually differntiators invert the output so it can help to compare signals if you invert the channel to correct it

>>1090498
thank you my man

>>1090478
you probably picked too easy projects

go for something ambitious and get stuck in, soon enough you might find yourself obsessed and it's much more satisfying.

>>1087877
Yeah ptobably

>>1090464
If i turn the pot all the way it should still work even if the resistance of the pot is too right?

>>1090537
Like he said, actual working range will be really narrow. Another problem is that 10k pot is designed to handle much lower current than a similar 100 ohm pot.

>>1090464
>>1090546
ok thanks

What is the typical through hole size on a PCB?

To make a long story short I want to make a few PCBs for guitar effect pedals, and I dont know what size micro bit I need to buy.

>>1090514
This
I still ahven't finished my linear power supply that i was going to build out of old computer power supply
>want diy voltage and current readout
>want better current limiting circuit (how?)
>want a tracking switching preregulator (how?)
welp

>>1088284
Assuming the partial power supplied to the FET is above the threshold voltage, it will still turn on, but the current output at the drain will be less than the saturation current. More voltage in = more current out (up to a certain point)

>>1090360
7 segment is probably way faster, yeah.
its just leds.

>>1090708
0.5mm is tiny and breaks easily, 1mm is kinda big for the most components. My usual go-to is 0.8mm, but it isn't that critical.

>>1090820
Oh, and in case it wasn't obvious, you're likely to need some bigger drill bits as well for stuff with thicker wires. For example, 0.8 + 1.3 + 2mm. If you have vias, you might want a 0.5mm drill bit for those.

This might be more /g/ territory, but does anyone have any suggestions for getting started with programming firmware? I was thinking about programming a controller for a keyboard. This a good project to get started or is that too complex for someone who has never written firmware?

>>1090966

simplest path is to learn PIC programming. go through the PIC catalog to find a chip that meets your requirements in
- supply voltage
- current consumption
- sleep modes
- number of IO pins
- cost
- RAM and EPROM size
- speed
- optionally: interrupts, analog inputs, PWM outputs

>>1090974
Thanks friend, I'll look into it.

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How does the node voltage equations behave here if I want to know Vab, which will be V2

My main concern is that Dependent voltage source in the middle. I know that its value will be: 160 (V2/40) = 4v2

Its just, I fail to visualize how to construct the node voltage equation.

how often do you breadboard circuits?

What are common faults I can look for when a device doesn't turn on?
Already checked caps, the power switch and power itself

>it's the controller for my electric drum kit, it worked fine a year ago, I just assembled it and it doesn't turn on anymore. Obv way too complex to debug if I don't find the fault in some visual way

>>1090363
do you need to measure DC? AC at something other than 50/60hz?
do you want to measure current in a multicore cable without seperating the conductors?
is a scale of "nothin'/somethin'/HOLY SHIT!" accurate enough?

>>1091022
almost never

>>1091027
Check voltages coming out of the power supply, take a close look at the board and see if there's any hairline fractures in the pcb

>>1091021
v1/60+(v1-(v2+160iΔ))/20=4
v2/80+V2/40=(v1-(v2+160iΔ))/20
iΔ=v2/40
Substitute for iΔ gives 2 equations in v1,v2.

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I want to get into making simple SOC's. Basically I want to buy individual parts like a microcontroller, ROM, RAM, timer, etc and connect them up on a board and load some code into it and run it.
But I don't know where to start. Can I just buy the parts and fiddle with them until they work or is there something I should read first?
I know boolean logic and computer architecture, but I've never played with actual parts before, I've only done stuff with virtual machines and logisim, and I don't know much about electronics.

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Can anyone explain to me how do i work with problems containing op-amps?

pic related: asks for vI depending on v1 and v2, taking into account that all resistances are known and the op-amps are ideal

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>>1091317
>Can I just buy the parts and fiddle with them until they work
Is this your idea of trolling or something?

Sure, you can make a board with a processor, memories, peripherals and shit. If you stick to the technology of the eighties, it isn't even that complicated. It still requires quite a lot of work to get it working and doing something actually useful. You need to drop that half-assed attitude to succeed.

>>1091325
my apologies if that offended you, but I have no idea how easy/hard it actually is. Which is why I wanted some advice on where to start learning and actually doing stuff.

>>1091321
Typically you assume the both opamp inputs are at the same voltage and work backwards from that to calculate the output.
For example, R1 in your pic has v1 volts across it, causing some current to flow. This current then goes to R2 and R5.

>>1091321

Write out the equations to determine the minus input voltages from the opamp output voltages.

Assume the minus inputs on the opamps are identical to the plus inputs (so V1 and V2).

Solve for the output voltages.

>>1091327
Well, it's not easy enough for random fiddling to produce any results.
You could start by googling "homebrew computer" to see what stuff people have built, how and how much time they have spent on it. That should give you at least a starting point.

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Does anyone know how i could implement a master volume control for an audio mixer?

The circuit to the left is similar to what i have going on; 2 channels with gain control for volume, exude the output pot. Can i implement a single pot which can control the 2 outputs simultaneously?

>>1091321
Whenever the non-inverting input is held at a fixed voltage and you have feedback between the output and inverting input, you assert that the voltage at the inverting input matches that at the non-inverting input (because negative feedback will attempt to ensure that this is so).

That equation indirectly describes the behaviour of the op-amp. When you assume that the op-amp has infinite gain, the equation Vout=gain*(Vp-Vm) becomes Vp=Vm.

You can actually solve the system for the finite-gain case, but what you end up with is just the infinite-gain solution made more complex by the addition of factors which typically look like 1/(gain+1) or gain/(gain+1) (which tend to zero and one respectively as gain increases).

>>1091403
A stereo volume control is just a dual-gang pot, i.e. two pots with a common spindle.

>>1091317
The terms "microcontroller" and "SoC" (system on chip) both refer to a microprocessor which has RAM, ROM (typically flash) and some I/O built into the chip.

The difference is that "SoC" generally refers to a PC-level system: 32-bit CPU, megabytes or even gigabytes of RAM/ROM, and high-level I/O such as video, bluetooth, etc. These are used in smartphones, tablets, set-top boxes, etc.

Microcontrollers start at 8-bit systems with 16 bytes of RAM, 128 words of flash, and a timer and go up from there.

You can get development boards with the microcontroller/SoC plus connectors, voltage regulator (if needed), clock crystal (if needed) etc, possibly with some circuitry to support programming them directly from a USB or serial port without needing a dedicated programmer.

I made a differentiator op amp circuit and an integrator op amp circuit. With the differentiator as the frequency increased the outputted wave form came to closer represent the input wave form and with the integrator the same thing happened as the frequency decreased and i don't know why

File: opamp34.gif (9KB, 520x204px) Image search: [Google]

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does the capacitor only exist here to serve as a low-pass filter?

>>1091510
The capacitor is a high-pass filter. But because it's in the negative feedback loop, it reduces the gain as frequency increases (the closed-loop gain is inversely proportional to the feedback fraction).

>>1091413
But dual gang pots have stray capacitance

>>1091521
>it reduces the gain as frequency increases
so in this set up it's a low pass filter you cunt.

>>1091602
Well if you literally mean just the capacitor then that's the function it fucking serves in literally every circuit. It's pretty much the reason you use capacitors at all is as a high pass filter.
So clearly the explanation of function was of the circuit rather than just the fucking capacitor shit brain.

https://www.youtube.com/watch?v=hkgu8wofYyM

>>1091631
breddy gud

>>1091631
Noice, but how do you make it display a linear sine wave?

>>1091744
>sin
>linear

why is /diy/ so mathematically illiterate?

>>1091775
a lot of diyers here do not pursue EE degree

>>1089223

I think you're looking for SRAM.

>>1087877
Are there jobs in your country for that skill set? If you live in North America your better off getting an EE degree.

Signed "a disenchanted electronic technician"

>>1088273
My first thought is transient noise. You may need to add some decoupling capacitors on your bread board.

>>1091775
Not all, but most of the people posting in /diy/ are tinkers not engineers.
No offense to anyone.

>>1087901
I got one of those. I like it but I can't speak for the accuracy or quality or whatever.

>>1087901
>>1091973
If you want me to check anything on it let me know. I can run some basic tests and such.

https://www.youtube.com/user/stangibilisco/videos

Big fan of
Stan Gibilisco does electronics, astronomy and amateur radio videos.

>>1091775
By linear I meant a sine wave displayed in a cartesian system of co-ordinates, not in polar or however you'd describe the funky figure-8s. The oscillations of the mirror are definitely almost sinusoidal in nature, but what mathematical description of their function could represent them in cartesian co-ordinates, or what mathematical description of their mystery system of co-ordinates, remains unseen to me and the aim of my question.

Also, "linear" can refer to anything "Arranged in or extending along a straight or nearly straight line", which could easily describe (the limit of) a sine wave.

>>1087810
Can anyone help me verify if this circuit would work? I only have experience working with residential wiring, so small electronics is a bit above my head. The speaker is rated at 8 ohms and 7 watts, and the power supply is going to be a either a 9 volt battery or 8 AA batteries wired in series. I was hoping to use this amp: uxcell® Super Mini PAM8403 2*3W D Class Digital Amplifier Board 2.5-5V
Would this work?

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>>1092159
Fuck. Circuit would look something like pic related.

>>1092159
As the board description says, it's meant to be powered from 5V. The data sheet for the PAM8403 IC gives the abs. max. supply voltage as 6.0V, recommended supply voltage 2.5-5.5V.

At 5V, it can supply 3W (per channel) into 4 ohms, so it will be half of that into 8 ohms.

>>1092167
So should I run a resistor into the circuit before the switch to cut down the voltage to 5V, then wire it into the speaker? Sorry if this is obvious, I just lack any really understanding of this stuff outside of basic Ohm's and Watt's law.

>>1092170
If you don't have a 5V supply, you'll need a regulator. A resistor won't work because the current draw won't be constant.

4.5V (3x1.5V primary cells) or 4.8V (4x1.2V secondary cells) would work. 6V (4x1.5V or 5x1.2V) would be pushing it.

The other simple option is a 5V USB "charger". Those are cheap and can run from a wide range of voltages. They tend to use switching regulators so if you run them from 9V or 12V, the current draw will be reduced proportionally (whereas a linear regulator simply discards excess voltage as heat, so the batteries will only last half as long).

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>>1092185
So if I wired 3x1.5V cells together, I would not need anything else to get this design to work? As in, I could just wire it straight to the switch-amp-speaker and be good to go? I really do appreciate the help, the small electronics math is a bit more confusing then wiring outlets and switches for a house. Have a smug anime girl for your trouble.

>>1092192
Yep, but measure the battery max voltage anyways, just to make sure. Rechargeables especially can be charged to over their normal cell potential, like how 12V car batteries are often over 13. They shouldn't peak past 5.5V, but you never know with chinkshit batteries.

As the other anon said, a 5V power supply is a cheap and reliable if you don't care about portability, and you could also take the two wires from a USB cable if it's meant to run off a computer. What's this for anyways?

>>1092208
I was going to try to get into smaller electronics after doing some residential wiring and learning a little bit about electricity in general, and I figured building a little portable speaker would be a cool way to get started. I found an old, old speaker in my basement that was wired for RCA, so I looked up some designs and figured it would be cool to wire the speaker for 3.5mm aux and make an old school portable speaker.

>>1092148
That's loose usage of linear. Nobody with first year level science education thinks like that. stop.

>>1092214
Nice project idea, I've been meaning to build one of those myself, but I haven't been fortunate enough to come across unwanted speakers.
>tfw I want to attach speakers to my bicycle
>tfw I want to blast eurobeats while weaving cars at 14ms^-1

>>1091041
Yes, no, is that something that you can find for under a couple hundred after 50% Fluke discount, I'm not designing shit for NASA or Intel but I also want it accurate enough that I won't have to replace it for being too shit for a while.

>>1092242
I won't help you with your assisted suicide project anon

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What kind of grease should I re-grease this with? Do I need special electrical grease?

It's a rotating vacuum hose connector with electrical contacts that were previously greased but I had to wipe it off to get a good enough grip to disassemble the thing. It seemed like it was just petroleum jelly or something. . .

>>1092264
Dielectric grease might work. I think it's unlikely the grease actually makes the contact, probably just there to help with the spinnin'. but I'm 4 beers deep so...

I need a highly programmable wifi-connected socket powermeter+switch. Have you guys seen any off the shelf stuff for this? More specifically, I need to program it to turn off the wall socket if it's both late at night and power consumption has been near zero for the last 10 minutes.

Assuming I have to build it myself, are there cheap chips that are made to do ac power monitoring? Or will I have to build a current sensor + voltage sensor and measure the phase difference myself?

>>1092310
power monitor ics exist but the ones i know need obnoxious external circuitry and use current transformers instead of simple resistors for measurement. they're also all smd. i doubt you could find one on a breakout board.

you can build your own all through hole with a latching relay, a difamp, 10-15 passives/zeners, a dip8 attiny or pic, and an esp8266. if the esp's adc is plexed you can probably skip the pic.

handling the latching/transmitting power peaks will be challenging with a capacitive power supply though.

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I'm thinking about recreating this circuit on a breadboard, but a number of these components don't have values, they simply say "NU".

Does anyone have any idea what this means?

(Its the korg monotron- the schematic is free online!).

Is anyone familiar with electrical connections that can rotate freely?
I'm mounting a mechanical part that has a servo on it onto the shaft of a motor. I want this part to be able to rotate freely but the cables of the servo motor would get entangled around the shaft.
I know about slip ring connectors but with the ones i find on eBay i don't see how they can help me in my setup.

>>1092436

probably means Not Used.

>>1092437

slip rings is the only answer. if you dont see how they can help, you need to look closer. there's a pic here >>1092264
gaze upon it and think about it until you attain enlightenment

>>1092437
>>1092467
Speaking of slip rings from ebay:
I can only find reasonably priced ones that are rated for up to 500rpm.
What happens at much higher rpm? Will it not be able to dissipate all the heat from friction and get too hot? Could I push it higher with active cooling then?

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Mad scientist here,
At work were getting rid of a couple xerox vendamat 7vg magnetic card readers. I really want to do something with them but I cant find a single bit of info on them. Anyone know how something like this might work? The connector is most likely proprietary, and theres an 8 pin din plug on the back that probably is also. Ill take one apart and post pics when i get home

>>1092520
brushed motors run past 500rpm. contact life decreases with increasing frequency though so there's probably not much commercial demand for slip rings at higher speeds. i'd imagine in the few professional applications where you *need* power transfer across a rotating joint that inductive coupling would be preferred. there's a million ways to get small signals across.

none of these solutions are very suitable for diy though so your only practical options are slip rings or reconsidering your design.

Hey guys, do any of you work as industrial electricians? Working with plc's and such?

I can see an industry that's screaming that it needs qualified technicians, and I'm thinking about trying to enter it. How did you get started? What qualifications did you get? What is your planned career trajectory?

>>1092555
>contact life decreases with increasing frequency
Simply because it's more rotations in the same time?
Or would also total number of rotations until breakdown decrease?

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>>1092578
the answer to anything involving moving parts and fatigue life is "it's complicated", so i can't answer that definitively though pic related shows a similar circumstance where higher rpm decreases cycles to failure.

regardless contact life in hours will be at least inversely proportionate to frequency

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>>1092467
>>1092520
>>1092437 here.

I found this slip ring which is a through bore one and it seems to be the one I need.
Problem is its $25 a piece and i need several, it seems ill have to drop the idea.
Im not mounting it on a high speed dc motor, just a nema 17.

>>1092605
Will the wires need to rotate more than 360 degrees?

>>1092642
Yes.
More so, it could spin at least two full turns before the wiring gets tight around the axis, but then it will have to unwind it self.

File: 50-cent spinning light toy.jpg (37KB, 500x500px) Image search: [Google]

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>>1092646

you might consider making your own. i've see diy PCB designs for this. cant be too hard, after all i see these spinning light toys at the thrift store for 50 cents all the time, still working after being abused by kids for years.

>>1092530
are you the same Mad Scientist who made the underwater hamster habitat?

>>1092578
> Simply because it's more rotations in the same time?
> Or would also total number of rotations until breakdown decrease?
The latter. Apart from more rotations in the same time, the surfaces are moving faster. So both more impacts and faster impacts.

>>1092265
Thanks, that's what my research has pointed me to as well. Off to the store to get some. . .

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I've been thinking about making a digital clock using BCD counters, 7segments display decoders and so on, just for the experience really.
Now, I was thinking about how to get a 10Hz (or 1Hz) to run it, obviously if I just slap an astable 555 in there to generate such clock I probably wouldn't get a decent one straight away. However, what if I deliberately set it to a higher frequency as precisely as I can, say 120Hz, and after that divide it using a binary ripple counter, theoretically I should get a fairly good clock reference in the end, no? After all the error would be divided as well, right? (I'm assuming the error "swing" is similar in both these frequency ranges, but I don't know if that's correct).

>>1092674
No, wouldn't they drown?

>>1092729
ah definitely not you then kek
no he had video of it and everything. this was from years ago before diy was a board

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>>1092726
I've thought of doing the same with a cool VFD 4-digit 7-segment display, but I would need many many ripple-counters / T flip-flops to the point at which buying a dedicated clock circuit becomes far more economical. Another prohibiting feature was that all four sections of that VFD tube were wired together, so displaying a "2" on one digit displays it on all of them. Displaying different digits was achieved through toggling through the 4 grids and the different numbers at high speed, which is a pain. Also Nixies look better than VFDs.

>>1092726
Resistors and such drift with temperature.
A 1% drift is still 1% no matter how divided down it is.
I'd imagine you need a crystal oscillator for that kind of accuracy.

>>1092736
Wow, that display is absolutely lovely.
>Displaying different digits was achieved through toggling through the 4 grids and the different numbers at high speed
Oh, multiplexing, yeah? Can't really imagine doing something like that without a microcontroller, but that would take the novelty aspect away, wouldn't it.
>Also Nixies look better than VFDs.
Yeah, Nixies are awesome.

>>1092742
I see. Thanks for the reply, anon.

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>>1092726
Errors don't divide that way. With an RC oscillator a lot of your error comes from changes in temperature. If it's going 1% too fast at 120Hz it's still 1% too fast when you divide that down to 1Hz.

The best thing to do is use a crystal oscillator and divide that down to 1Hz. 4060 is a binary counter for clock division and oscillator you can hook a crystal to all in one chip.

You can divide by an arbitrary number of you can't find a convenient crystal. Say you need to divide by 100. In binary that's 1100100, so AND together bits 3,6, and 7 and run that to the 4060's reset. It will count up to 100 crystal oscillations then reset itself.

You could also try getting the 120Hz of the AC lines. Power companies keep that stable because most clocks run that way.

>>1092753
I guess I will go with this circuit then, thanks anon.

>>1092726
Crystal oscillator. Clocks normally use a 32768 Hz crystal, so a 15-stage binary counter will divide it down to 1 Hz.

The other option is to run it from an AC wall-wart and use the 50/60 Hz mains frequency as a time base. The mains frequency isn't perfectly accurate, but the variations are supposed to cancel out (i.e. if it's 60.1 Hz for a couple of hours, they'll slow it down to 59.9 Hz for a couple of hours to compensate). That's how electric wall clocks keep time.

>>1092744
>doing something like that without a microcontroller
While they went out of fashion years ago, there are dedicated ICs which take 50/60Hz in or have connections for a crystal and then drive a 4 or 6 digit multiplexed display.
One of those chips was MM5309, but it's now out of production. You can still get it (or some of the related chips) from ebay.

Not that it is that difficult to do display multiplexing with 7400 series chips, but the result will be big and clumsy.

>>1092242
Yeah, I was really fortunate to find them. I was cleaning out my father's workshop and found them hooked up to an RCA car stereo converter. The radio has a belt melted into it, so I am working on that, but in the meantime I figured I would put the speakers to good use.

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>>1092859

Question from electronics noob here. Replaced 3 bad caps on the inverter for my monitor. Now after 30 minutes of work lcd backlight turns itself off while monitor still functions (enters standby, for example). I assume there is an overheating issue somewhere but I can't figure out why it worked fine with previous bad caps just until I changed them.
Anyway, when backlight turns off on 22v power rail my multimeter reads 28v, and when it's working properly (for 20-30 minutes after some time of inactivity) it reads 22.
What should I look for? Any advice would be greatly appreciated.

>>1092530

magnetic strip cards are very simple

you can view the digital data written on them with fine iron filings

they probably are very similar to a cassette player or VCR and you could probably make one nowadays with a micro controller ADC

Does anybody know were to find some disassembled 8080 assembly so I can test my 8080 assembly interpreter?

>>1091587
yeah, and?
the output of your opamp will charge and discharge those few picofarads so fast it will have no effect on the sound

How do I learn to read circuit schematic properly?
I cant get over it that a schematic isnt the physical representation of an actual circuit layout.

>>1093373
Why does it bother you? The actual layout doesn't affect the circuit's behaviour at all (until you get into high frequency stuff, that is). Just look at the schematic and note which components are connected, and which of their respective pins are connected. Schematics are made this way because its literally the simplest way to depict the circuit, mate.

>>1093378
>Why does it bother you?
Because then I have to design my own layout.

>>1093393
Which is preferable if you plan to diy the board yourself on a perfboard or whatever.

>>1093393
Any worthwhile PCB design program has the ability to ensure that the layout matches the schematic.

>>1093321
it's possible your caps have too much esr when warmed up. that would produce increased ripple in the supply output that could peak at 28v as the controller tries to compensate. the supply might be running at 100-400khz so you'll need a scope to check this.

>>1093378
>>1093395
>>1093400
I find something like pic related much MUCH easier to read.

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>>1093430
and ofcourse I forgot the pic

>>1093432
no idea how you do that though, schematics are the simplest most elegant way to show circuitry, this is just a ratsnest and you have no idea what pins are what etc

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>>1093435
I do refer to the circuit schematic to see what is what, but in terms of connections and shit I find this one easier.
The pic i posted was a headphone amplifier. and the schematic is a fucking dick to read because its made only for one channel.

>>1093437
so? you just take everything twice

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>>1093439
as you can see in >>1093432 theres a single tube. and THAT is what confused the fuck out of me when I was trying to make a schematic of two channels combined.

Stuc kat pic related.

>>1093089
What is that PCB under the breadboard?

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What's your opinion about using this transistor (type BD 136) for controlling standard 60..120 mm, 12 VDC computer fans from microcontroller output pins?

>>1093460
if the fan is 4 pin, it already can be switched through an internal mosfet

>>1093460
you can't drive a pnp at 12v from a uc input, they're not 12v rated and will need another external npn to manage the pulldown resistor for the pnp. juse use an npn. preferably one with higher gain, but whatever.

>>1093407
Well, for some bizarre reason it started to work all by itself. Thanks for the info anyway!

>>1093489
electrolytics are fabled to have a burn in period if not used for a few months, that might have been it.

i think it's electrolytics that experience that phenomenon at least, could be ceramics.

>>1088066
What are you doing for a dev environment with your esp board? I've been using the arduino-esp8266 for mine, since it was easy as hell to setup. BUT, I'm having issues getting at the depths of the wifi chip, and at getting the finer grained control of the PWM outputs.

>>1093500
Does the ESP8266 even have hardware pwm?
It's really lacking in I/O

>>1093505
For some reason I thought it did, so I just tried to look it up again ,and came up with software-only, no hardware PWM. I'm very confused now.

What's the easiest way to generate an audio-level signal? I was thinking of using a 555 to make a square wave, but I'd have to get a beefier voltage inverter to get it two-sided around 0V. Is there a chip that'll do it for me, for example?

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>>1093509

>>1093511
GOOD point

>>1093511
I seem to lack the capacitance to understand your answer.

>>1093509
http://electronics.stackexchange.com/questions/133993/how-to-make-lc-tank-circuits-oscillate-continuously
And put a speaker on the output and mess with the resistance values. It's what I'm going to use to measure the inductance of a hand-wound coil, so tell me if it works.

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>>1093517
I'm going to go with something like this. I'm sending it to a 3.5mm barrel connector and then to an actual audio amplifier so I have to attenuate the signal but I'm not too worried about that.

>>1093521
About that signal attenuation - I'm planning on using an inverting op-amp with low gain to get the 5V square wave signal to around 20mV peak to peak. Does it make any real difference if the coupling capacitor is before or after the op-amp? I'm guessing before is better since there's no reason to add impedance after the amplifier, but it won't be a huge difference. Can anyone confirm?

>>1093450
Just a power supply, logic probes, sine generators and things. It's an educational board with breadboard from my university

>>1093536
100 uF at 10 kHz is 0.16 ohms, hardly a significant impedance contribution

>>1093545
Oh, I see. What a cute little thing, wish I could have one of those.

>>1093548
http://www.elexp.com/ProductDetails.aspx?item_no=32VPTADBRD&CatId=

I'm guessing you can buy it from here?

Or maybe check Ebay, students will sell them there occasionally. Usually called an "Andy board"

>>1093536
Why use opamp in the attenuator? You could just use a 2k2 + 10R voltage divider. Sure, it would have ~10R output impedance, but that shouldn't be a problem if you're driving an external amplifier.
The DC removal capacitor before the divider can be pretty small. 3.9u would set the -3dB frequency below 20Hz.

>>1093554
http://harbingerproaudio.com/wp-content/uploads/2014/03/Manuals/Harbinger_HA80_Manual.pdf

The amplifier's impedance is listed as 8 ohms. I was assuming that's the input impedance, so the current through that 8Ω would screw up the voltage divider.

But now I'm doing a little more research and that 8Ω might be the output impedance, since I think speakers are generally 8Ω so that would maximize power on the load. I looked up a $25k amplifier's specs and it's got like 10kΩ input impedance. So maybe the one I have also has a really high input impedance and didn't bother listing it?

Please let me know if that's right; I really don't want to go through the trouble of setting up an op-amp and voltage inverter, or figuring out single-sided supply.

>>1093556
Amplifiers typically have high input impedance and low output impedance.

>>1093558
Yep, 10kΩ impedance on aux in. Simple voltage divider coming right up.

Thanks. You've saved the city.

>>1093553
Unfortunately I'm from Brazil, so importing something like this would probably be very costly and bothersome because of taxes, mailing, customs and whatnot. Thanks for the info and links though, I truly appreciate it.

I found a copy of the Make: Electronics book recommended in the OP at a local thrift store recently, and I was wondering if there was a list of all the stuff that is needed for all of the "lessons" in it. I don't want to wait for stuff to come in, so I'd rather order it in one go. I also might already have some of the stuff.

Hello, I'm building my first electronics project and I have a few questions. The project is a motion activated cat litter box ventilation system.

The grand scheme is to have my arduino activate a relay which switches on a fan when it a motion detector detects a cat in the enclosure. The fan will blow through a dryer sheet or something

Right now I'm in the planning phase. I have an old laptop ac/dc converter that says its output is 18V and 2.2A. I know that I can divide this voltage into 12v (for the fan) and 6v (for the arduino). I also need to reduce the current to 0.2 amps. Therefore I need a 100ohm and 50ohm resistor in series, correct? Then the two pieces would go in parallel with their respective resistors?

I found two resistors like this but I think they were too small and when I made the circuit, they started to smell and get too hot. So I think I need higher rated resistors. Do I base that rating off of the specs of the ac/dc converter? Does the converter act as a current and voltage source?

Pic related is a back of the napkin sketch of the circuit

Any help is appreciated. I just want my cats' shit to stink a little less when I get home from class and learn a thing or two in the process.

Thanks

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>>1093625
Image

>>1093625
>>1093627
I honestly cannot tell if this is some kind of elaborate baiting or if you're just that innocent, but I will bite anyway.

You shouldn't use voltage dividers for that purpose, never. Use a LM7812 and LM7809 for the voltages you need.
I don't know if that's what you meant by that image, but an Arduino cannot switch a relay directly, you will need a transistor for that (you could also just forget about the relay and use the transistor itself to switch the fan, a BC337 would do).
You don't need to limit the current to the fan, the specs just mean that at 12V it draws 200mA.

As >>1093639 said.
12v/100 ohms = 120 mA
P=I^2*R= (0.12^2)*100=1.44 watts
Bad idea.

Try looking at some community projects where they interface with Relays. Or use a transistor as a switch. Use a voltage regulator for 18V-5V for the arduino

>>1093639
>>1093643
Thanks guys, I'm not trolling, I just didn't know where to start

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Can anyone give me a hand with this mosfet circuit?

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>>1093694

there was just a discussion above about how schematics are a million times better than component layouts, and you show up with this monstrosity.
kindly redraw this as a proper schematic. rats' nests not welcome here.

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>>1093694

oh, it's a vape circuit. looks like they doubled up or triple up on all the FETs to make it easier for the batteries to explode in your pocket.

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What's the deal with the DC offset on this circuit? Voltage is measured at R7, the load. Shouldn't C4 be removing the DC component?

The low bits are an 800Hz square wave, and the high parts are a 500Hz square wave. Why is the frequency changing the DC offset of the signal so much? Is it because the changing impedance of the capacitor is messing up the voltage divider?

If it can't be fixed, what effect will the DC offset have on the sound of the signal? R7 is an audio amplifier.

I assume I could use an op-amp with <1 gain instead of the voltage divider, but I'd like to avoid it for simplicity's sake.

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>>1093719
Screenshotted the wrong window.

>>1093720

so the simulator throws an 11mV disparity at you, which may or may not be real. on the larger scale of things, how important is that, compared to the fact that it's 2016 and you're listening to 555 audio, like it was 1970?

>>1093720
An audio amplifier is probably AC coupled to begin with so I doubt it will matter much

>>1093723
What's the alternative? This is part of a circuit which I want to keep close to $5 so microcontrollers are out.

I don't know enough about audio to know how big of a deal the offsets are.

>>1093725
Oh, good. If it's not, what's the worst that'll happen? Bad sound? Blown speakers? House burns down?

>>1093728
>what's the worst that'll happen?
You'll waste my time more.
Build it pussy

>>1093726
>how big of a deal the offsets are.

you couldnt tell the difference by ear even if there was a $1M reward for doing it.

>>1093730
Thanks.

>>1093729
Eat my jorts.

For the sake of learning, I'd appreciate if anyone can tell me why the offset is there.

>>1093735
Transients from your big ass capacitor friendo.
Change the 100 uF to 10 or 1 uF and it will be more centered around 0 volts. and as >>1093730
said. You'll never notice

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guys tell me if im stupid or solder an smd resistor on an xtal is normal

>>1093719
>Shouldn't C4 be removing the DC component?
Yes, but it does not mean that the resulting waveform's positive and negative peak values will be the same. For example, a +2V/-1V square wave at 1/3 duty cycle has no DC component.
One of the nuisances of the 555 is that it requires special pampering to produce symmetric square wave.

>>1093785
wtf????
they soldered a resistor to an xtal case?
a case soldered to ground is OK, but that?

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>Hard wiring dash cams
I want to hard wire it to a 12v line, probably the cigarette lighter. The camera runs on 5v.
What should I use to convert it?
Or should I just wire the cigarette plug it comes with into the back side of the cigarette lighter port?

>>1093824
Dash cams usually run on 12V, but if it really needs 5V, you can just get a cheap BUCK step-down converter from eBay, they cost like $1
http://www.ebay.com/itm/DC-DC-LM2596-power-Supply-Buck-Converter-step-down-module-GM-/262136732989
If the cam comes with a cigarette plug, it should very much be 12V though

You can use the fuse box for 12V that is active only when ignition is one, but it's just down to whichever is more easy to wire

>>1093838
Thanks m8
>0-40v in
>0-40v out
Don't know why I haven't been using these for everything

>>1093853
Just keep in mind the amp/watt rating, and that this specific type only steps down, of course there are stepup and also ones that can do either stepup or stepdown, and ones that have current limiters and whatnot. They're also not super efficient, the efficiency ratings the ebay sellers give are usually best case scenarios or straight up bullshit. But they are definitely useful.

>>1093854
>>1093853
You should buy one that isn't generalized (i.e. its fixed for a constant output at 5 volts, and a small input range between 10 and 15 volts)

Those tend to be much more efficient since they're calibrated for that specific voltage range

How do you gain the intuition for electronics? As in to be able to look at a schematic and just imagine the flow of current. And being able to compose your own schematics due to having a feel for what components do.

I got a book - Electronics From The Ground Up by Ronald Quan - thinking it would help but it's shit.

It just throws schematics at you and just basically says "this works, take my word for it and build it" without giving you any insight.

It's literally Giving A Man A Fish: The Book. Waste of fucking money.

It's also got this obsession with building circuits just by stringing components together by their legs. It doesn't just mention it once or twice, as a curiosity - it doesn't fucking shut up about it.

I'm not doing that shit. I've got breadboards and protoboard and a soldering iron. I'm not going to sit there daisychaining some fucking metallic spaghetti junction.

>>1093785

they may be trying to hide the crystal's frequency from view to make duplication harder.

>>1093888

but it's literally just a board wrapped around an FTDI chip

it was likely made for that exact application and they probably just made the circuit exactly as it appears in the datasheet

plus, how hard can it be to measure a crystal's frequency with basic tools

>>1093887
You gain intuition by analyzing circuits and also by building and testing circuits, that's how you get to the point of "oh, from that previous circuit I know that this and that can be achieved using this kind of configuration, so maybe I will try that and combine it with that to do this" and "oh, I've seen something similar before, this is is probably serving that purpose".
Instead of just building the circuit, try to analyze why/how it is working, and how are all the parts of the circuit interacting which each other (generally you can simplify things in blocks).

>>1093719
What makes you think there /is/ an offset? You can't see the duty cycle in that mess. Bear in mind that the DC offset is the average (integral divided by period), not the difference between minimum and maximum.

Ctrl-left-click on the graph label (V(n011)) will pop up a dialog displaying the average and RMS values.

>>1093896
I see what you mean but I want to try and understand each component in isolation first - its fundamentals.

I understand capacitors in that respect, and so how they work in conjunction with other things, but transistors and the like just don't seem to make sense at all.

>>1093911
Resistors, capacitors and inductors are all linear and have two terminals. The current and voltage can be described by a simple first-order differential equation.

Transistors have 3 terminals and are decidedly non-linear. Unless you're writing a generic circuit simulator, you tend to rely upon approximations (e.g. for an NPN BJT: Vbe=0.65V, Ic=beta*Ib). Sometimes you need more complex approximations but design mostly revolves around setting up the conditions so that the the simple approximations work (e.g. biasing).

>>1093911
Then google is your friend, just search for pages dedicated to the topic or question you have in mind. Either that or search for more specific books/studying material.

>>1093918
I was gonna get The Art Of Electronics but cheaped out and got that other book. Big mistake probably.

I don't know why electronics is so hard for me. I picked up coding easily so I thought I'd have the right kind of mindset.

I've done some simple things with electronics, like made circuits with 555s and even Arduino stuff but most of it bamboozles me.

>>1093925
>The Art Of Electronics
Been wanting one of those for a long time too.
>I've done some simple things with electronics, like made circuits with 555s and even Arduino stuff
I'm of the opinion that buying an Arduino as a beginner isn't a very good thing to do, at least not if your objective is to learn electronics. I mean, it's really useful and convenient but you end up jumping a lot of "steps".
> but most of it bamboozles me.
That's normal in the beginning.

>>1093925
If you want a better understanding of the passive components, check out Physics for Scientists and Engineers by Serway and Jewett.

http://gen.lib.rus.ec/book/index.php?md5=8CDC793B6B0D83729E67E79FB48E7632

That's the book I learned from in high school, and what really got me into the field.

>>1093893
This,
If I had to hazard a guess, it was cheap way to alter the frequency for what ever reason.

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>>1093466
Thanks for your reply. Pic related, would this kind of arrangement work?

>>1093978
Yes.

Although if you're driving it with PWM, you should also have a pull-up resistor from the base of Q2 to its emitter (BJTs turn off faster if you actively drive Vbe to zero rather than just cutting off the base current).

If it's just an on/off switch, it doesn't matter.

>>1093838
How is DC stepped down? I know transformers only work on AC.

>>1093927
>you end up jumping a lot of "steps".
Ain't that the truth. The temptation to write code to do something a few components can do is strong. I wrote an object that smooths the input from the analogue pins, instead of making a filter.

>>1093946
How bizarre, this page is blocked by my service provider.

>>1094001
Power electronics. Imagine you have a DC voltage at 5 volts and you have a circuit that is cutting on and off very quickly. You get a bunch of +5v, 0v pulses, you filter and smooth out these pulses a bunch of times and then you get a DC voltage again but at something maybe like 3.3 volts

>>1094004
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwj719PcsdvQAhWHg1QKHevCC-UQFgghMAE&url=http%3A%2F%2Fgearju.com%2F225768904560%2FData%2FPhysics%2FSerway%2520-%2520Physics%2520for%2520Scientists%2C%25207th%2520Ed%2520-%2520GearTeam.pdf&usg=AFQjCNGaTlpNYLnbJBuEontMJDPDENfU1A&sig2=NQ2h5KHxqn1kkwRHrcVvdQ

>>1094006
Clever shit.

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>Little things that piss you off
Farads are fucking huge, working with things in the micro and pico range is tedious

>>1094358
adding 1E-9 to everything in matlab sucks, but if you didn't know you can type units into the chrome url bar and it'll solve for you right there. add a "to uF" or "to MHz" at the end of the equation for output conversion. i use it for all my unitized algebra.

>>1094003
>I wrote an object that smooths the input from the analogue pins, instead of making a filter.
Hahaha, really?
Never heard of something like that before, how do you do it? Averaging samples from defined intervals, I suppose?

>>1094396
alternatively: use your brain idiot.

>>1094534
keep a running queue of samples, each time a sampleis added fft to convert into frequency domain, remove bins associated with undesirable frequencies, convert back.

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I need d2 in the picture. but i don't know how to select forward and reverse voltage on digikey. can someone give me a partnumber or aliexpress link?

>>1094537
Hah an FFT and IFFT? How about a lowpass filter

>>1094564
Yes that is the traditional way but as they say when all you have have is a dsp everything looks like a frequency domain problem

>>1094536
epic!

solve 300V/(4.44*31mm^2*150mT*450khz) in your head, freshman trash

>>1094568
The more usual way is direct convolution with a FIR or IIR filter.

FFTs may be used (via overlap-add or overlap-save) if the convolution kernel is particularly large and you don't need low latency.

>>1094534
Real author of >>1094003 reporting.

Was just a circular buffer implemented in an array that returned the average of the buffer every poll. Rather than recompute the average every time, it just subtracted the average of the difference, every "frame".

>>1087810

new thread

>>1094602
>>1094602
>>1094602
>>1094602
>>1094602

>>1094588
But that wouldn't have been as unnecessarily complicated for the purposes of the joke, to clarify I made it up as a joke because I was bored. I wasn't the anon who posted about it to begin with.

>>1094358
just work with units of pico farads = 1 or picofarads = 1E-3 or something instead of Farads = 1

>>1092148
Yeah because trigonometry, a linear change in input amplitude won't give linear translation of the laser dot.

>>1093511
How on earth can Take That help?

hi ohm/
I have a question about AC and power factor in normal households.
As im studying EL on my own, i don't really have a teacher on the subject.
I'm writing an assignment, calculating the power need, input and circuits for an apartment
My book is says;
finding the right amount of fuses needed, calculate the total power consumption with the power factor.
but my book doesn't tell me where to find the PF.

I get that PF depends on if its an ohm resistance in a circuit, or a inductive resistance.
but what type is there in households and where would i find the PF?

every example in my book is from some sort of ACengine with the PF already given.

thanks in advance for any help!