/ohm/ electronics general - red, hot, and dripping solder

Reposting from the last thread

I'm trying to a build an ADB to USB adaptor, I've got a SparkFun Pro Micro which just has wires shoved in to the big curly cable coming from my SMK Apple Keyboard II. I've got VCC and GND on the Micro connected to the right pins on the ADB cable and I've got a 1K Ohm pull up resistor between VCC and the data cable which is plugged into the right place but as far as which port on the Pro Micro I'm supposed to plug it into goes I have no idea so I phoned a friend and he said port 5.
Everything's done according to
http://blog.jomon-lab.com/arduino-projects/adb-to-usb-adapter-using-arduino-keyboard-function/wire-connection
and I've flashed the arduino ok.
What am I doing wrong? When I run it, it just prints "AYYYY".
Should I be connected to pin 6 on the SparkFun? How am I supposed to know which pin to use? How can I go about debugging this? The tutorial says port D6 so I'm according to http://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Pro_Micro_v13b.pdf I should be using the fourth port from the bottom of the right hand side of my board?
I hate asking for help but I don't know a whole lot about this kinda thing and don't know where to start, help me /ohm/, you're my only hope.

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>>954644
Forgot pic

>>954644
Ayyy lmao
>If using Arduino Micro and Leonardo board, PORTD6 is DIGITAL PIN12

>>954652
But I'm using a SparkFun Pro Micro?
There is no pin 12 on the board, there's a12 but that doesn't work.

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>>954644
>>954645
Ayy senpai
>>954668
Pin 12 is digital pin 12.
You get the schematic I sent you?
Anyway, dumb question time.
I have this little shitty 150w inverter and I wanna test it on an oscilloscope to make sure it isn't too horrible, but it's got this universal plug on the front, not one for any specific country.
I'm just wondering which pin's active and which one's ground, if it even matters in an inverter.

>>954675
>Anyway, dumb question time.
There where meant to be a million empty lines before that, what happened to all them

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>>954675
Pulled the cover, turns out they made it easy for me.

>>954687
Also, if I keep it on battery and it's isolated it shouldn't matter in the least.

Is there anyway to heat something with an arduino?

>>954875
you don't even need a tarduino for that

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would be a decent logo

>>954878
probably not, but I left out that I need something to heat up when a PIR motion sensor goes off and the easiest way to control both would be to use an arduino.

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> Is there anyway to heat something with an arduino?

i got one of these for free: a 1A LiPo hand warmer with 2 heating coils. if you wanted it to be Arduino control, you'd need to use a power FET as a switch to the heating elements.

>>954898
>heating elements
where can I get one of those?

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>>954904

amazon for one. mine came from an outdoors-type store, WindRiver.

http://www.amazon.com/HotPod-Rechargeable-Pocket-Warmer-Sleeve/dp/B00I4OFGR6

you could also pull a foot of nichrome wire from a thrift-store hair driver, but you'd need something to isolate it.

>>954904
Cheap hot glue guns.

>>954917
Operating at 120V? I'll Shirley die.

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>>954921
>Shirley

>>954921
They usually are insulated enough but you should always have a ground/earth cable on the metal you attach it to, to make sure you won't shirley hurt yourself.

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Question about salvaging electronics here,
tommorow i will have an hour to get anything i can out of an old house that will be torn down, the thing is that there are still appliances like freezer, oven and so on in there.

What is the most useful thing i should look out for? Or should i just cut wire down and sell it at a metal trader?
I am fairly interested in your replies.
Things like radios and tvs will not be there, although all the lamps are still in there.

>>954934
Scrap is pretty low lately but grab all the weight in copper you can get. Also look for copper pipe. Steel and iron aren't bringing shit at least in eastern US. I only got 65 bucks for the most recent car I scrapped, and I brought it to the yard.

>>954934
if you could rip the cable out of the wall you could make like $10-15 scrap
if you could rip it all out in an hour i'd give you the money myself
appliances probably aren't worth the bother if they are still there, donate them to a charity shop. nobody will buy a second hand freezer from you plus you have to clean it and shit. not worth the hassle.
unless you want to i guess

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>>954936
>>954937
Not really looking for selling these as a whole, if have a small car and won't be able to get much in there. I ment like take them apart on the spot and get useful things for diy projects like power transformers or motors.
I never really took such things apart other than a clothesdrier so i don't really know what i will find exactly.
So it's more for the hobby than making money.

>>954566

What's a good small microcontroller with ~5 I/o pins and a cheep programmer preferably available in DIP

>>955002
lpc810

>>954939
You could look for engines. A freezer and fans could be a good place to look. If there's anything electronic in there (as in tv's microwaves and stuff you could potentially strip those of odd capacitors since those should use custom made parts.
If there's anything relatively new there could be power diodes and tiristors which can be useful.

In any case, just take everything and post profits.

>>954882
Fair enough, but you don't heat something "with" a uC. You might use a uC to turn a heater on/off, but that's just the general "interface logic to power" problem. Which is definitely something you should learn if you want to actually do anything with a uC and you don't want to be limited to plugging together pre-made shields like lego.

>>955051
Alright thanks for the advice, i am going to post results in a few hours for sure.

>>955002

The ATTiny stuff should work for you. They're available in 8-pin DIP and can be programmed with a 20 dollar programmer from sparkfun

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>>955051
>>954934
In the end i ended up not getting my hands on electronic components but i found a training wheel, complete pocket bike parts with a working motor and an automatic door opener, i also took off a satellite dish and found even more stuff.

I started ripping out cables from the wall but quickly realized that it wouldn't be worth it, i had access to about 10 flats and people just left stuff laying around.

I am fairly excited to look into the automatic door opener, the rest will be sold and the bike fixed.

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>>955206
This is the bike i was talking about, not in the best condition but that can be fixed.
Sorry if it's not really related to the thread anymore, just wanted to post the results.

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I've got a 24V load I want to drive off a 240V supply using a Switch Mode Power Supply.

However, I also want to be able to continuously vary the power to the load.

1 - what would I search for for a part that could convert 24V dc to 0-24v dc, based on a control signal? Do such things exist?

2 - alternatively, should I just use a duty-cycled solid-state relay instead? Are smps happy to feed into a duty cycled load?

>>955380
if you are driving it off 240v what are you going to use as a supply voltage? why tell us what you are not going to power it with instead of what you are?

anyway

usually smps is fixed voltage
there are smps that will run open loop for a specified draw and closed loop for variable current draw but maintaining the voltage.

>>955384
Huh? My supply is 240V AC.
Yeah, I didn't expect to find a smps that would have that feature. I'm looking for a seperate part -
A variable buck converter is what I want, I suppose - one that I can adjust through a control signal of some sort

>>955392

you still havent mentioned what the load is. if we knew, we might be able to recommend a PWM controller, or a variable regulator, a rheostat, or whatever. spill the beans, fag.

>>955380
Variable resistor between PSU and load.

>>955380
Programmable power supply or programmable regulator (the former tends to refer to AC-DC supplies, the latter to DC-DC).

The better (and more expensive) bench PSUs can be controlled via IEEE-488 (GPIB) and/or USB. This may be beyond your budget, though.

For a PSU "module" (which will be somewhat cheaper), most of them will be DC-DC, i.e. you'll also need a fixed-voltage PSU to convert 240V AC to ~30V DC.

You could build one yourself (there are lots of articles on building PSUs on "maker" sites). In this case, you should definitely build something which runs off low-voltage (<50V) DC rather than mains.

If you want to control it with a voltage (rather than digitally), you could try modifying a fixed-voltage supply by replacing the reference voltage with your control voltage. This will be easier for a DC-DC supply than AC-DC (isolating topologies tend to have a relatively fixed voltage ratio).

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Hey /ohm/, I've got a project I'm doing requiring a ~100w power supply so I just bought a cheap AC adapter capable of delivering 120w with the male size being pic related, this is my first time working with a laptop adapter for a project and I can't seem to find the female connector equivalent for it, I barely know what to search for on google.
Or should I just cut off the current connector and just buy a male/female pair and solder on instead? pls halp thnx

having trouble identifying value of SMD/SMT capacitor from laptop mobo. top reads:
470
EFK
3Y6

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>>955658
this is a similar one found on ebay, looks like this but marking is different so im not sure of value

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>>955658
Pic would help. If it's like pic related and around 10mm in diameter, it could be a 470µF 25V electrolytic capacitor, from Panasonic.

>>955662
Oh. The last line is just a lot code in Panasonic's capacitors.

>>955663
>>955664
thx m8, not even sure if it's blown, looks like the one on ebay , no electrolytic residue though. top looks flat except for those vents? read somewhere that these were meant to hold together when they swell instead of popping and spilling

can anyone help with determining a capacitor size?
mate of mine installed sequential turn signals in his car which do the sequence, but they also keep blinking like regular turn signals. which i thought could be negated by using a capacitor but i cant find any info on determining capacitor sizes.

its a led strip about 25cm long, would estimate about 10w? at 12v.

>>955655
They're generally called "barrel" connectors. Those dimensions seem to be particularly uncommon, so your best bet is probably to replace the plug.

>>955676
that's not going to do what you want.

>>955685
i thought the capacitor charged up in the on state and discharges when it is off, atleast thats what i learnt at school on how to rectify ac>dc voltage
what can i do to get the desired effect?

I'm looking for a voltage output module but I don't know how to find what I'm after.

I need something that will put out 0-10V on many channels (looking for 140 but don't mind buying several) to provide control signal to some PWM relay modules. I want to control it via SPI or i2c.

Is there a specific term for these sorts of parts?

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Could anyone please help me identify what kind of signal this is? I tried NFM modulation but it just made a noisy sound.

>>955708
It is a single of a whale

Just in case you guys haven't noticed yet, Dave on EEVBlog posted a video about an Oscilloscope giveaway.
Agilent is giving away 500k worth of Oscilloscopes this month, one every day.

>>955689
Digital-to-analog converter (DAC). But they won't go up to 10V (so you'll need level shifters) and you typically only get 8 to a chip (so you'll need 18 of them).

But why do you want variable voltage? What exactly are you trying to drive?

>>955737
Well that's neat. I doubt I would ever use all the functions on one of those things, but it would certainly beat the hell out of using my shitty half-broken single-channel 50 MHz analog scope.

>>955808
Personally I'd sell the thing the instant I'd get it.
It's literally worth $14k.

The fuck would I use a scope like that for anyways.

>>955813
tripfagging probably

>>954566
Can bad capacitors make a bubbly hiss buzz noise?

Ive got this monitor that Ive been needing to replace caps in for a while, I left it take apart.
short story is I needed to see if the scree just got shattered so I put it all back together and now when it turns on its making this noise Ive never herd it make before.
could this be the caps or is something else fucked up now?

>>955784
I've found plenty that will do 10V, but as you say 8 or 16 seems to be the limit per unit. Oh well.

I have a bunch of pulse-width-modulating solid-state relay modules that accept a 0-10V analog control signal.

Maybe if I look hard enough I can find some similar things that accept digital control signals?

If a DC motor controller wants a 0-5V control signal, is the PWM output from an arduino good enough for that?

Or will it require an actual analog level?

Motor controller in question:
http://www.united-automation.com/content/X10335%20-%20DCM24-40%20%286%29.pdf

>>956009
Can the arduino put out a pwn in the correct range?
how many ma is the controller expecting? iirc arduino is limited to 5v 50ma

>>956011
It's only small, according to that datasheet it should only draw 1ma from the control input.

>>956032
I dont mess with the stuff, but if the arduino can modulate the output wihtin the acceptable parameters of the controllers input, then Id imagine you could make it work.
if you have allot of stuff running on the arduino you might see some lag, but I really dont know.

Consider an arduino. Pwm pin into a vco.

>>955976
> Maybe if I look hard enough I can find some similar things that accept digital control signals?
They're called MOSFETs.

Seriously, it sounds as if you just need to drive a bunch of FETs with PWM signals. The "modules" are presumably a FET driven by either a VCO or a sawtooth generator and a comparator.

But that just replaces the problem of 140 analog signals with 140 PWM signals.

But if you don't need a high duty cycle, you may be able to use a matrix arrangement to reduce the number of signals.

It also means that you can use almost any microcontroller, with the number of outputs per chip being the number of GPIO pins, minus two or three for the SPI or I2C interface.

>>956009
> If a DC motor controller wants a 0-5V control signal, is the PWM output from an arduino good enough for that?
You can just low-pass filter the PWM to turn it into DC. An R-C filter will probably suffice.

>>956145
>But that just replaces the problem of 140 analog signals with 140 PWM signals.

Depending on the other requirements, LED drivers could be a semi-reasonable way to produce 140 PWM outputs.

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I would like to mod a usb charger to work with apples. All schematics I found on google use two separate voltage dividers. Would pic related work? It's much easier to fit two resistors than four in limited space.

In an RC circuit, to charge a capacitor, is it better to put the resistor on the positive side "before" the capacitor or "after" on the negative side of the capacitor?

A resistor burned out on my capacitor charge circuit (despite being well within the allowed wattage) so I replaced it with one of much higher resistance and there is now no voltage difference between either leg of the capacitor and the ground. I currently have the resistor "before" the capacitor.

>>956184
It makes no difference.

>>956184
>there is now no voltage difference between either leg of the capacitor and the ground
A device that causes no potential difference between either leg is a wire, not a capacitor.

Are you sure it's only the resistor that burned out?

>>956178
apples don't need electricity to work, you can rinse them before you eat them though
>inb4 linux on an apple

>>956230
>>956184
Capacitor is fine. I just checked and it holds a charge.

>>956329
It may be that your "much higher resistance" is so high that it supplies less than the capacitor's leakage current.

How did you determine the power rating for the original resistor? It should be V^2/R, where V is the supply voltage. When the capacitor is empty, the full supply voltage will be across the resistor (i.e. the capacitor will look like a short circuit).

>>956178
I mean it probably doesn't matter, but no those are not the same. If the device tries to communicate it will drive the two wires to different voltages (and they will always be different because they're a differential pair) which means you're shorting it out.

>>956178
Yes, it is true that Apple devices, for whatever dumb fucking reason, need a 2V signal in the data line or something like that in order to recognise that they should start charging.

A resistor divider will work.

https://youtu.be/wdgiTQffiwk?t=4m22s

>>956553
The different voltage dividers across the D+/D- pins tell the device the current capacity of the charger.

If the USB SIG had stepped up and invented a charger specification before (rather than several years after) Apple needed one, I guess they could have used that instead.

See also Lightning/USB-C.

Anyone here do any rf circuit stuff?

Im looking to get into rf stuff and wondering if anyone has any suggestions

What the fuck is a "polyester" capacitor? Going through the BOM of a kit to place a Mouser order and it lists all these "polyester" capacitors whose part number Mouser can't find.

".001uF (2A102) polyester capacitor" is what the line says.

Are polymer caps commonly referred to as polyester caps in Taiwan?

More importantly, can I just sub in a ceramic cap of the same resistance? It's just a Roland 303 clone.

>>956479
IIRC it's mentioned in some usb specification that shorted data line indicates a charger. Most decent devices should be smart enough to detect that, and random china junks don't even bother checking data line anyways.

>>955655
you can get cheap jacks in two types

breadboard/pcb:
http://www.amazon.com/dp/B00KLDQ3XO/
screw terminal:
http://www.amazon.com/dp/B00R96X6HC

the latter is high quantity but i've bought a 5 pack for less than a dollar shipped before

>>955686
the capacitors in power supplies are only off for a short time so they don't have to store much energy

if you want to get rid of the blink you'll have to find the thermal switch that makes it blink and short out its two terminals with a wire

>>956618
> What the fuck is a "polyester" capacitor?
A capacitor which uses polyester film (PET, Mylar) as the dielectric material.

> Going through the BOM of a kit to place a Mouser order and it lists all these "polyester" capacitors whose part number Mouser can't find.
> ".001uF (2A102) polyester capacitor" is what the line says.
2A102 is the abbreviated value, not a part number. 2A = 100V, 102 = 10e2pf = 1nF = 0.001uF.
On Mouser, look under Passive Components - Capacitors - Film Capacitors.

> Are polymer caps commonly referred to as polyester caps in Taiwan?
No. Polymer capacitors are solid electrolytic capacitors.

Polyester capacitors are referred to as polyester, PET or Mylar. Also not to be confused with: polystyrene, polypropylene or polycarbonate.

> More importantly, can I just sub in a ceramic cap of the same resistance? It's just a Roland 303 clone.
Check the working voltage and ESR. Polyester caps tend to be cheaper than ceramic at higher voltage ratings, and typically have lower ESR (which matters for power filtering capacitors).

>>956615
It's kinda broad topic, but you might want to check the ARRL handbook. It explains the beginner level stuff pretty well.

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First year student here
so I have an alternative current generator producing very low output(micro to nano amp)
what would be a way to made it visible to a voltmeter ?
pic related, the output in amp

>>956768
A big sense resistor + high impedance voltmeter would be the most obvious choice. 1M resistor would give you 1V/uA scale.
Or you could build a transimpedance amplifier, if the resistor voltage drop is unacceptable.
Or in some situations you could replace the sense resistor with a sense capacitor and a buffer amplifier. Or turn it into an integrator. Either way, you'd end up integrating charge.

>>956768
1uA will produce 1V across a 1MΩ load. An oscilloscope or digital voltmeter will be significantly higher than that. An op-amp with the output connected to the inverting input (i.e. unity-gain buffer) can be sevaral GΩ, but you need to allow for input leakage current.

OTOH, if it's more like 1nA, then good luck measuring it. Apart from anything else, the signal is likely to be swamped by interference.

>>956768
Googling "measuring nanoamperes" gives results which appear relevant.

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Has anyone ever ordered a custom PCB from Seeedstudio or similar?

Did you really get 5 or 10 PCB's for $10? I have a feeling the "per board" part was lost in translation since it seems too good to be true.

>>956723
Ahh so they are under the Film section. Thanks!

>>956793
No but i believe on tinysine you still get 10 for 10$ aslong as they are a certain size.
I left 20$ there and got some nice boards.

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I've got this funky looking motor here that I took out of a paper shredder along with some nice microswitches, anyone seen anything like this before?

First pic is the rotor. Note the brown and blue wires. I don't know what they do. Maybe speed control by way of "brake pads"?

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Here's the rotor mounted inside the stator.

>>954676
>There where meant to be a million empty lines before that, what happened to all them
4chan culls most whitespace. I think it allows for 1 or 2 empty lines in a row max. Fuck knows why, whitespace is damn near free.

>>956945
it's so people can't spam huge boxes of blank text.

>>956938
the brown and blue wires supply electricity to the rotor windings via carbon brushes known as a commutator.
in this case the rotor and stator are both electromagnets
don't ask me what this setup is called i can never remember the names.

>>956959
Thanks man, pretty nifty.

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Hypothetical scenario.

I have a 5VDC blower fan I want to run off a USB port.

The fan is rated for 150mA. The port has a current capacity of 500mA.

Do I have to do anything fancy to control the current or can I just solder the wires from the fan directly to the cable that goes into the port?

Also, what kind of pot can I use to vary the speed?

>>957161

use a multimeter to check the current

if it's above 500 ma you need a resistor.

just get a 5 watt pot with minimum resistance

what get as first multimeter?

>>957169

fluke 87

What is a simple easy project that a complete beginner could use to get in to doing this stuff?

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>>957193

stick eight consoles inside an R2D2 unit. easy.

>>957169

you dont need no stinkin' multimeter. if it says 150ma and you have a source of 500ma, you have a mountain of headroom. no need to measure anything.

>>957193
Some people start off by making an amplifier, or circuits with leds.
Something useful that is not very hard to build would be a battery tester.
Make sure you understand what the components do and do not just build stuff or it could be frustrating if something doesn't work.

>>957170
>fluke 87
ahahaha, you very funny

>>957211
A proper USB host limits dumb devices to 100ma unless they negotiate a higher demand.

Cell phone chargers aren't proper usb hosts so they don't give a fuck, but if he's using a computer it actually won't be enough.

>>957169
Depends? Do you have a Harbor Freight near you? If so, they almost always has a coupon in their flyers for a free cheapo meter with any purchase. It's one of the better products they sell, and it's pretty good for free-fiddy. I try and get one any time I can so I can loan them out.

Otherwise, I'd say go on amazon and look at meters in your price range and read the reviews.

>>957242
Such proper ports seem to be rare on computers. IIRC you shouldn't actually draw even that 100mA before the computer allows it (or after it disallows it), but I haven't seen a single PC to prevent that.
Even 500mA limiting seems to be a hit and miss.

No idea if the hand held devices are more anal with their current limits.

>>957253
> IIRC you shouldn't actually draw even that 100mA before the computer allows it (or after it disallows it),
That would create a chicken-and-egg problem. In order to even negotiate power consumption, you need some kind of circuitry, and that circuitry needs power to operate. So every device is guaranteed at least 100mA, and can request more (how much depends upon the version).

Hosts aren't required to enforce the power limits. But if you're selling devices which draw more than100mA without actually negotiating for it, you're liable if it fries someone's PC (and it would be unwise to use any of the official USB IF logos on your product).

>>957161
> Do I have to do anything fancy to control the current
Provided you're willing to ignore the bit about negotiating for over 100mA (which will work, just don't plug it into a bus-powered hub), you don't need to actively control the current.

But you might need inrush current limiting, particularly if you're planning on powering it from a PC (desktop or laptop) rather than a "charger" and you don't want to fry the PC. A NTC thermistor may suffice if you can determine the inrush current behaviour (which will require the use of an oscilloscope), otherwise you'll need an active circuit.

> Also, what kind of pot can I use to vary the speed?
You probably can't vary the speed just with a pot. 5V fans normally use "brushless DC" motors, which are actually 2-phase or 3-phase synchronous AC motors designed to be driven by a controller circuit, and the circuit will require a certain voltage to run. You *may* be able vary the speed via PWM (the controller circuit can just filter this to get 5V DC, and use the duty cycle as a control signal).

>>957261
>That would create a chicken-and-egg problem.
It wouldn't, since there's still the 500uA suspend current available. For example, FTDI's FT232R USB-UART bridge supports this by providing an output you can use to disable the rest of your device on suspend.

Well, I don't remember the details, I might be wrong on something and I can't be arsed to google the full details of the expected suspend behaviour. So, take it with a grain of salt.

>>957277
Suspend/resume are designed so that a suspended device doesn't require the ability to speak or understand USB protocol (i.e. you can power down the uC during suspend). Suspend is indicated by 3ms in the J state, resume by 20ms in the K state. This much could be handled by one 74-series chip and a couple of passives.

In theory a device is supposed to honour suspend/resume, although I have no idea whether any of those USB-powered LED reading lamps or similar actually do so. A suspended device doesn't have to "do" anything, so I should probably have qualified that "100mA guarantee" with "while functioning".

If you want to be totally legit, you can use something like a PIC18F2550 to negotiate the power consumption and handle PWM control of the fan as well (you could even allow the PC to control the fan speed). But I think the guy is trying to do this without any actual electronics involved.

>>957239

why not

you'll end up buying one anyway

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What is pin 4 supposed to be doing in this image?

The full diagram is on page 22 of this:
http://akdatabase.org/AKview/albums/userpics/10004/Pioneer%20SX3800%20Service.pdf

>>957169
A Fluke 8010a is $30-40 on ebay.

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Do you guys like my soldering station? I rest the soldering iron on steel wool after wiping off excess solder

>>957381
Could it be an antenna?

Hi fellas

I have a question. I have a couple of young nieces for whom I'd like to make a music box that plays Christmas songs (starting earlyish). I'm getting into hobby electronics and I figure this could be a cool project.

Ideally, I'd have 3-5 songs to choose from, using buttons, and a power switch, running it on a 9V or something.

What I'd like to do is use a microcontroller, and drive a speaker at different tones for different amounts of time, creating a recognizable song. I happen to have a few Arduino Pro Minis lying around, and figured I could use one of those.

However, I've heard that it's bad practice to use a square wave to drive speakers/buzzers due to harmonics, and that you should use a sinusoidal input instead.

In short, my question is how do you generate a sine wave at various frequencies using an Arduino?

>>957381
shield

>>957381
It's the signal ground on the inputs to the power amplifier stage. Pins 3 and 5 are the actual inputs, around which pin 4 should be the coaxial screen.

Note that the signal lines are labelled I and J in the PCB layout but F and G in the schematic.

>>955655
im trying to add more batterys to my psp
by wireing 3 2600 Mah 3.6v batterys in paralell to the chip inside of the original battery (required for psp to boot) will the original chip be able to handle the exra mah or should i wire one battery to the chip and the rest to the console
do you think this will this work
the recipe calls for 3.6v but will 3.7 work

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Just came into possession of 19 1N277 diodes. Checked ebay and they apparently have sold for $1.75 each and are usually listed for $3-6 each. Keep or sell? If keep, what use for?

>>957421
NEVER wire lithium ions in parallel. Just don't.

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Hi guys

I have a broken hand vacuum that i want to re-purpose. I opened it up and beside the dead batteries it seems fine.(see pic) I am planing to use the motor to make a cold smoker.

What would be the best way to power the DC motor ?
Ideally I would like it to be battery powered the problem is that I do not have the original adapter.
I went online and looked around and i soon realized that the regular AA/C/D cells were not were nowhere near powerful enough to supply the current needed. the only thing i could find where some specialist drone batteries but i have no idea how to charge those. what would you guys suggest?


I am sorry for failing this hard, this is my first time working with electronics.

>>957461
>specialist drone batteries
You mean lipo cells?

get a lipo charger and plug them in. buy quality cells that have overcharge and undercharge protection.

>>957444
are you retarded? you can equalize the voltage by just charging them to within 0.05+/-V then connecting them with a 10ohm resistor and leaving them for an hour. this way you get perfectly balanced cells.

>>957464
That's assuming they discharge identically, which they won't.

And what the hell do you think will happen when the device tries to charge them?

>>957461
>>957462

Lipos are pretty expensive.
Since this is not something you will be using every day i would suggest a cheaper solution. Replace the original batteries and find the correct adapter.

>>957464
>>957468
thanks for the input i think i'm going to do it anyways

>>957469
> i would suggest a cheaper solution. Replace the original batteries and find the correct adapter.

that's not a cheaper solution. for hand-held devices the cost of a replacement battery is almost equal to the cost of a new device. an actual cheaper solution is to find a 5V @ 5A power supply, such as the one from a dead computer. no more toxic batteries needed. the dude can use 3.3V instead if he doesnt need full power.

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>>957461
>I went online and looked around and i soon realized that the regular AA/C/D cells were not were nowhere near powerful enough to supply the current needed.
IDGI. The diagram shows that was what was there originally, and (presumably) they must have worked fine.

http://www.farnell.com/datasheets/13542.pdf <-- these NiMH D cells can happily output ten amps for an hour.

>>957461
"Industrial" NiCd/NiMH cells can handle that current. Packs used for emergency lighting (4x C or D cells with shrink wrap and wires) are probably the easiest to obtain.

Consumer-grade cells tend to have built-in current-limiting to prevent fires in the event of a short circuit (NiCd D cells can put out 100A when shorted, which can easily happen if you just drop them in a box/draw/etc of largely-metal junk).

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>>957404
It's not "bad practice", it's just that the sound isn't very good.

If you output a 1kHz square wave to a speaker, you'll still hear 1kHz, but with a lot of higher-frequency components mixed in, albeit at lower amplitudes, since any square wave is a sum of several sines, see pic.

>>957621
Though presumably you can cut them out with an RC filter, just like the greeting cards do?

>>957625
RC filters don't work for *all* frequencies.

They should work for a short range of frequencies tho.

Doing something like http://www.learningaboutelectronics.com/Articles/Square-to-sine-wave-converter-circuit.php may work if you're only going to be using frequencies around 10 KHz.

>>957737
Or you could do a low pass filter with cutoff at 2kHz and avoid the whole situation

/diy/ im struggling on something stupid. Im trying to make a rail splitter circuit with TLE2426 with 12V supply. Its powering a quad opamp of which total current being outputted from the op amp is less than 1mA. However when I test this circuit on multisim the op amps get all distorted and I cant even do a simple op amp circuit. When I use a BUF601 it works but I don't want to use a BUF because they are so expensive. I tried a rail splitter circuit with an op amp as well and got the same results as TLE. I don't understand why BUF would work when my circuit needs barely any current. Thanks /diy/

>>957404

you can make a table of sine values and put it on an external SD card, for which i think you need a separate add-on board. then, read from the card and output to 8 outputs with a weighted resistor network to create a simple digital-to-analog converter.

this, however will sound like shit. sine waves are crap. you need polyphony (multiple tones) to make sound interesting. so a better idea is to convert WAV files of the songs into 8-bit data, and save those on the SD card. at 16,000 samples a second, you can fit a ton of songs on a 2G card.

>>957820

we'd like to see the drawing so we can laugh at whatever newbie mistakes you've made.

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>>957762
What if you're trying to deliberately play a note at above 2kHz?

Sure, it may be possible to have the system play only mids and lows with a simple RC filter approach, but you'll be damned if you also want decent high-pitched sound.

It may be possible to have different speakers and each has a different low-pass RC filter that cuts off at different frequencies, but that's just increasing system complexity.

>Irrelevant text here, I just want to thank /ohm/ for existing since we can actually have discussion here that's more meaningful than the "what do I buy and where" cancer that /g/ has become over the past couple years.

>>957404
> In short, my question is how do you generate a sine wave at various frequencies using an Arduino?
First: does the Arduino have a digital-to-analog converter (DAC)? If not, you aren't going to get an actual sine wave out of it.

If you don't have a DAC, then you need to either use pulse-width modulation (PWM) or delta-sigma modulation. Either of these needs to be followed by a low-pass filter.

Then, you need a digital oscillator. The simplest of such is
[code]
t = cos_a * x + sin_a * y;
y = cos_a * y - sin_a * x;
x = t;
k = 1/hypot(x, y);
x *= k; y *= k;
[/code]
where sin_a and cos_a are the sine and cosine of a=2*pi*frequency/sample_rate. The above would normally be implemented using fixed-point arithmetic rather than floating-point.

The last two lines form an automatic gain control to ensure that the signal amplitude remains constant. hypot() can be an approximation based upon the fact that the result will always be close to 1.

Alternatively, you could just use square waves and tolerate the distortion, like most cheap bleeping gadgets do.

>>957869
I would go with the different speakers set up because it'd probably sound better desu senpai

>>957869
No need for multiple speakers, just multiple filters.

But even an Arduino can do reasonable delta-sigma conversion in software at well above audio frequencies. It's not going to be CD quality, but it will be better than square wave or PWM.

>>957589
>>957584

hm, ok that seems like a good idea.
Can i put them in a regular D cell charger to charge them?

So, I've been working on a YouTube series to try and teach electronics from an engineering perspective to absolute beginners. Would you all mind if I shilled it here?

Would love some feedback and corrections if I get anything wrong. My first series is going to be over electromagnetics.

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I have a bunch of hard disks, a bunch of the same model of enclosures, and a 2P6T switch.
Is pic related a good way to wire the switch so I can just put it all in a box and use the switch to select a disk?

>>958029
no
just plug them all in

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I'm very new to this.
Can someone tell me why a 2position switch has 6 connectors?

Can't find anything with the serial (ARCOLECTRIC T1460VA, T125 series)
and am kinda confused by the 10(3)A.
As I said I'm new to this. Where can I educate myself besides the OP copypasta? Have to work a lot so I ask specific stuff.

>>958035
Why?
And I only have 2 power plugs, I'm tired of switching em around.

>>958037
http://www.learningaboutelectronics.com/Articles/Toggle-switch-wiring.php

>>958039
thank you. I searched for something similar earlier but ran out of time soon.

>>958029
You'll need a 4P6T switch (SATA uses 4 signal wires; switching the power and leaving the signal wires connected won't work and may damage the drive or controller), and the host controller needs to be capable of hot-plug. And the switch will need to have the appropriate characteristics (i.e. not too much parasitic capacitance or inductance, and not too much crosstalk between connections).

Or you could use tri-state buffers. But all things considered, it's probably easier to just get a controller card that can handle 6 drives.

>>958042
Sorry, my initial post wasn't clear. I have several enclosures which can all run off the same 12V wall wart, which has just 2 power wires.

>>957992
> Can i put them in a regular D cell charger to charge them?
Separate cells, yes.

For a battery pack ... it's probably easier to just cannibalise the pack for the high-current cells (they are just standard C/D cells inside the wrap). They're designed to be charged in-situ, so standalone chargers aren't particularly common.

Since bike dynamos can drive a 3W incandescent bulb, can I use one with a big cap and a 5V regulator to charge shit?

>>958043
Actually, I overlooked the part about enclosures; my reply assumed bare drives.

For USB/eSATA enclosures, you can just switch the power. For 2-wire power, a 1P6T switch would be fine (you only need to switch the positive line, the ground can be left connected).

Just ensure that the current rating on the switch is sufficient.

>>958050
I have 2 2P6T switches lying around, that's why I mentioned that one. I'll doublecheck the current rating, thanks!

>>958045
You could, but if you're going to the trouble of doing that, you may as well start with something that puts out more power. Almost any permanent-magnet motor, DC or AC, can be used as a generator.

Charging batteries is more complex. You typically want constant current rather than constant voltage. You could just use it to power a separate charger, but then any power capacity beyond what the charger draws is wasted.

"Energy harvesting" basically revolves around getting the maximum power out of whatever energy source you're using then converting it to whatever form is useful.

>>958054
Oh, one other thing: multi-throw switches come in two main types: break-before-make and make-before-break. With the former, the common connection is connected *at most* one other terminal (when changing position, the existing connection will be broken before the new one is made, resulting in a period with no connection). With the latter, it's *at least* one other terminal (the new connection is made before the previous one is broken, resulting in a period with two connections).

If you have the second type, the current rating needs to be enough for two drives to handle the change-over. Unless you consistently power off the whole thing before changing drives (which is probably a good idea anyhow, so that switching from drive 1 to drive 6 doesn't briefly power up drives 2 through 4 in turn; they might not like it if you do too much of that).

>>958059
There is no amp indication on the switch. But it looks robust, I have similarly build switches that are rated for mains current. This one will at most see 12V/1.5A
I was indeed planning to turn off the power before switching, that's why the extra switch is in that drawing I posted, to prevent any funny stuff.
Thanks for your input!

>>958056

I have a few motors from printers, rated at 24V though.

CC vs CV wouldn't depend on battery chemistry? I would probably use Ni-Mhs as they aren't pissy, or a very small SLA from a flashlight. This would then go to the charger.

>>957830
here it is, the circuit is just a active bandpass filter with a gain of 200 centered at 10Hz. Like I said bufcirucit gives no distorted waveformbut the TLE does. I got circuit schematics from Audiotangetsoft.net

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>>958069
>>957830
fuck sorry here is the image

>>958009
>My first series is going to be over electromagnetics
Always start with ohm's law.

If current is uniform across an entire circuit, and charge is invariable, and electric potential energy is due to similar charges being in close proximity to one another, then why isn't potential energy equal at all points on the circuit?

>>958245
Because different segments of the circuit have different resistances, and the voltage drop across them is directly proportional to the respective resistance.

If every segment had the same resistance, then yes every part would have the same voltage drop.

Source(s): Ohm's law.

>>958251
I know, but I'm just saying that if there's the same number of electrons shoved into the same amount of space on either side of the resistor, shouldn't the potential energy remain the same?

>>958253
>>>/sci/
I don't think any engineer really cares about electrons.

If we did, then we wouldn't be dealing with conventional current flow.

As long as our mathematics and measurements add up (no pun intended), we are satisfied.

>>958240
Well, it'll lead into that. This kind of explains where ohm's law comes from.

https://youtu.be/lPDOrFuQD3g?t=37m28s

At 37:28 he's confused by a logarithmic plot, wtf. I thought he was an engineer. Surely he's seen a log scale before. Man, he's really gone down hill lately.

>>958330

To be fair I don't even get log scales although i've seen them millions of times

>>957386
does it actually save you up to 50 dollars a year in energy cost?

>>957386
Don't use steel wool, it'll fuck up your tip. Use those brass things instead.

Whats a good fpga trainer board i can get to learn verilog/vhdl?

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>>958295
Ohm's law and Kerchov's laws are basically essential for electronics. With just those any newb can start understanding deriving how many other things work. They're very simple to explain too.

Ohm's law is a single equation you can manipulate to figure out different things. Kerchov's current law is "Everything that goes in must be equal to everything that comes out", and the voltage law is literally "the sum of voltage drops between any two points is equal to the potential difference between them".

>>958330
I think he's more annoyed (not confused) by the fact that it starts with fucking 0Hz and that the gap between 0Hz and 1 Hz is taking up half the screen. Most semi-log graphs (pic related) start with 1, because who the fuck cares what's going on at 0.5Hz.

>>958345
They make sense once you start dabbling into anything involving AC signals like RF and audio.

captcha 420

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http://www.sound.westhost.com/articles/class-g.htm

>>958376
>Kerchov

>>958065
> I have a few motors from printers, rated at 24V though.
Hmm; printers typically use stepper motors for the vertical feed, and sometimes for the head movement, those won't work as a generator.

> CC vs CV wouldn't depend on battery chemistry?
No. They all want roughly constant current.

> I would probably use Ni-Mhs as they aren't pissy,
NiMH can be trickle-charged at C/10 (i.e. their capacity in Ah or mAh divided by 10 hours, so it takes ten hours to fully charge an empty cell). At C/10, they won't be damaged by overcharging.

You can charge them faster than that (up to C/3) but you need to detect when they're fully charged and stop charging (or switch to trickle charging). Cells which charge at C/1 have a microchip which talks to the charger, and need a specific charger.

The main issue with just using an off-the-shelf charger (or a passive trickle charger) is that it will want a fixed voltage and draw roughly fixed current. If the voltage (under load) is too low, it won't operate, and any excess power will just be discarded.

A more advanced solution would extract as much power as is available and dump as much of it as possible into the cells. Typically, that involves a constant-current switching regulator whose current is controlled by a combination of maximum power-point tracking (MPPT) (to extract the maximum power) and battery monitoring. Which isn't rocket science, but it's not just wiring stuff together.

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>>958429
I like to pretend he's Russian

>>958376
>Ohm's law
I like that one, especially when you use complex numbers to work with AC networks. That's the best one for the newbies! :D
Anyway, yes, that stuff is essential.
>>958009
>electromagnetics
If it's a basic introduction about electric/electromagetic fields and the work they do, plus how a conductor works, then it's ok, but don't make it too over-complicated.

>>954914
>Heating element directly on lipo
I'm sure that's safe and good for longevity

>>956938
You know what a stator is but not a commutator? At least you're curious. Keep learning! Basically the blue and brown wires touch those copper pads one at a time as they spin by, supplying current to one section of coil. That section of coil creates a magnetic field that pushes off another magnetic field, rotating the coil until the brush contacts the next copper pad, electrifying that coil. It's like a switch.

>>958376
>he can't spell kirchoff

>>958594
kek

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I need to generate two reasonably stable reference voltages for an application. The higher voltage (3300 mV) is used as a reference for A/D converter, while the lower voltage (2250 mV) will reference an instrumentation amplifier.
I assembled this circuit on a breadboard and it seems to work well. Is there anything that could be improved?

>>956938
So I just opened my drill to clean all the swarf out of it, and the commutator looked like that. Staining was evenly distributed, like in the picture. No grooving or apparent wear. Brushes had about two-thirds left on them. But when I was using it in a dark cellar, sparking was visible at high load. No unusual smells. Is it okay?

I'm guessing it's better to leave it alone than clean it for no reason?

>>958376
>current law is "Everything that goes in must be equal to everything that comes out"
1+1=2
>voltage law is literally "the sum of voltage drops between any two points is equal to the potential difference between them".
2=1+1

I know it must have been groundbreaking at some point, but really?

>>958672
>reference voltage
if the current demand is low you can replace it with a 2 channel dac with laser trimmed voltage source but you have to program it.
have you calculated temperature dependence?

>>958679
Plot twist: you can combine the two laws and derive that the sum of power in a circuit = 0

>>958679
well i didn't see you coming up with it

I'm converting my old tube radio to a guitar amp. There is an external speaker output and I want to use that to connect it to a guitar speaker cabinet. Now I want to remove the internal speakers because those will break when attached to a guitar. But the thing is that you can never turn on/use a tube amp without a speaker attached to it. So is it possible to replace the internal speakers with resistors of the same resistance?

>>958732
Don't tear apart a still functioning tube radio man, that'd be like that San Fransisco "artist" who destroyed a WW2 1911 to make it into the last piece for his sculpture. Just get some 12AX7 tubes or something.

Could you just route the internal speaker's wires to your external speakers?

>>958735
>implying a San Francisco artist wouldn't do that

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I posted this a long time ago but I didn't get any reply, I need a retriggerable one-shot circuit (or similar) to filter out the noise made by a 433MHz reciever to obtain a clean HIGH or LOW signal. The idea is to let the noise retrigger the circuit providing an stable signal at the output, as soon as the noise drops to 0 the circuit should change state.
TL;DR:
Reciever-> Noise ->Circuit-> Output LOW
Reciever-> No Noise ->Circuit-> Output HIGH

I can't use 555s since the voltage I'll be working with is 5 volts and I don't have CMOS ones, ideally the circuit must consist of discrete components and consume a low amount of energy.

>>958723
Guess I must not have been alive in the time of Electror, Cat of Electricity.

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Are these worth picking up? I'm not ready to drop >$100 on an old bench scope, but I'd like to have a go at reverse engineering displays.

>>958876
low pass filter. if you want better performance, you need active components. use the sallen-key topology. for better performance, use a dsp.

also, dat 1054. don't forget your license hacks.

>>958885
if you're not ready to drop $100 on a scope, you're not ready to reverse engineer displays. protip, with an analog scope, you can get really good performance in x-y mode to make it a display. grab a video sync seperator, some transistors, and some capacitors, and you're on your way to reading composite in on your scope.

>>958885
I have a DSO138.

I bought it mostly just to have fun assembling it. I haven't used it for anything at all, actually.

Usability is pretty crap, spend good money on a bench scope.

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>>958904
Speaking of having fun assembling it, does anyone know of any projects I could do that involves lots of soldering?

I do enjoy doing soldering.

>>958920

LED matrix/cube.

I thought about building a 32x32 matrix, but I'm not overly fond of soldering and I figured I'd just put that on the backburner until I finished my pick-and-place machine.

>>958735
That's the point. I want to keep the as original as possible. So no new speakers. I want to make a switch that switches between the resistors and the internal speakers if that's possible

>>958962
Anyone?

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>>959007

yeah, one input + 1 DPDT switch = 2 outputs.

all the grounds just connect together. if that's a problem, then you'd need to switch the grounds as well, so you'd need a 4PDT switch.

Hello /ohm/, a few questions

It's hard to find liquid flux where I live, paste form is much more abundant. How to use it, though? I stuck it in a syringe but it doesn't seem to do anything - though I clean all my surfaces before soldering, use flux core solder and I have no problems, and I don't yet do SMD. Is flux even needed in that regard? I assume it'd be useful if I were to solder a new cable to an old, oxidized one, but is that it?

Also, my laptop fan broke some time ago so I bought a replacement, but the broken one fried the controlling circuit. I bypassed it by - feel free to laugh - soldering a USB plug to the fan (it's a 5V fan), breaking a hole in the plastic enclosure of the laptop and connecting it to a free USB port.
I want a more elegant solution, so I'm thinking a DPDT switch to either connect it as it is now, without a resistor for maximum speed and the second throw would be connected through a resistor for more casual use (it's loud as shit now). Can anyone think of a different idea? I don't want to buy a 1W pot for that, and there's no space for a PWM circuit.

>>959243
What about ghetto rigging a Thermistor somewhere near the heatsink and using that as a voltage divider for the fan?

>>959256

I'm not looking for actual usability. The laptop works like shit after it's been overheated, hangs up on most applications. However, I like pressing buttons, so buttons are my preferred solution.

Hi /ohm/,

Staring a personal project that involves bluetooth and looking for a good microcontroller. Doesn't need very many extra peripherals since I can par it up with other stuff but having trouble finding a good one.

I've used the TI CC2540 BT micro in my last job, but it required expensive software to code for it so hoping for something that still has support but I can program it for free.

Anybody have any suggestions?

>>959243
Flux for smd just keeps the solder where is supposed to be instead of shorting things out. Get some rosin core solder to clean as you solder and forget the flux.

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>>958050
>>958059
>>958062
Seems to work, the drives spin normally and no magic smoke.
Now all I need is a usb hub and build a box around it.

>>959243
https://www.youtube.com/watch?v=vIT4ra6Mo0s

Flux is difficult to find for me as well, but it's really only essential if you're working with difficult joints or SMD.

Otherwise, the flux in your flux-core solder will be sufficient for hobby work.

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>>959353
>Mini USB
JUST

GOD I FUCKING HATE MINI USB

>>959359

Anon that's not mini USB, that's your standard USB B

>>959364
immediately after posting I typed up a followup clarifying that I meant type B, but that I do also hate Mini, but it appears it did not get sent.

>>959359
>>959367
I hate mini too, but why the hate for B?

>>959369
Because fucking nothing uses it, it's completely worthless when type A exists, and the pin card, the thing in the middle of it with the pins on it, is too easy to break due to there being a million miles of clearance on either side.

>>959370
I see a lot more broken A and micro connectors at work. Never seen a broken B now that I think about it.

Hey guys
I need just a 24V DC simple on/off solid-state switch relay module

All the ones I see are specced for AC - but is there any reason why they can't also be used for DC? They're either just mosfet or phototriac based.

I'm not familiar with triacs honestly - if they're on DC, will it be possible to open them?

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I need your help /ohm/.

I need to source pic relateds, in small bulk. They're piezo microphone elements (not piezo contact mics!). They're made (or used to be made) by Kobitone, and companies like Astatic before them. Mouser doesn't carry them anymore, and the one guy I know who hoarded a whole stock of them has sold out and closed shop.

Even alibaba has yielded nothing. Where do you guys buy your components? I need to know where to look and my current livelihood depends on it D:

Examples:
>Kobitone 25LM022
>Kobitone 25LM024

I have 140 thermistors that I need to read
But I don't want to pay for 140 analog inputs
I need to multiplex the voltage across them into one analogue input, right?
How do I find something that will do that for me?

>>958895
Thanks, I tried using a simple low pass in combination with a transistor and it worked well until I discovered garage remotes trigger the thing accidentally, I bought a couple of LM567s (bandpass filter IC) the plan being to send a pulsed signal with the transmitter to be picked up by the sensor and accepted by that IC, the noise should automatically be rejected. Now I have the LM567 all wired up and the output doesn't wants to go high (it's normal state) even without an input signal, I guess I'll figure this out.

>also, dat 1054. don't forget your license hacks.
I didn't, thanks to our lord and saviour, Dave.

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>>959382
Is that not just one of these with a metal plate over it?

If they're not manufactured anymore and nobody has a big stock of them, drop them and pick something else.

>Noob questions incoming

Can anyone explain why I'd ever use an Arduino over a microcontroller IC?

>>959404

because tarduino is easier than using a real microcontroller

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>>959396
no it's not one of those. what you have is a moving coil dynamic speaker, which could potentially be used as a microphone were it more sensitive. the thing i need is a light diaphragm (like your little mylar speaker cone) but it vibrates against a ceramic piezo element (usually with a little rod between the two so it "pokes" the piezo). they have a very distinct sound that certain people love, even though the technology is obsolete.

if i switch it to something else the whole concept is kaput, sadly. pic relates - my salt & pepper mics (lo-fi old-timiey rochelle salt crystal mic - salt, carbon granule mic - pepper)

i might have to look into making my own crystal elements from scratch D:

>>959404
No need for an in-place programmer

And some small amounts of supporting components

https://www.arduino.cc/en/Tutorial/ArduinoToBreadboard

>>954566
I have 2 questions :
1) I have a simple circuit with a 5V battery input and a switch. I would like to add a LED to this arrangement so that when the circuit is ''on'' the LED glows. Ofcourse i dont want to compromise the 5V input to the main circuit. Do i attach it in parallel or how ?? Help me please

2) What is the best temperature for soldering basic components like LEDs and resistors.

Thanks in advance.

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>>959567
>Do i attach it in parallel or how

you wire it like so, after the power switch. for the resistor, it depends on the color of the LED, but 330-ohms should work for any color.

> What is the best temperature for soldering basic components like LEDs and resistors.

the temperature that your soldering iron puts out. trust the the manufacturer to know what he's doing. you wouldnt ask the same question about a toaster, would you. just dont use unleaded solder, it is an exercise in frustration.

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>>959570
I have one of those soldering stations where you can set the soldering temperature. Never used those before. I had a standard soldering iron which worked wonders but doesnt anymore.

So something like pic related ??

>>959376
> I'm not familiar with triacs honestly - if they're on DC, will it be possible to open them?
Sure. It's closing them that's the hard part. A triac turns off when the current through it falls to zero. For AC, that happens every half-cycle.

MOSFETs should work fine with DC (although one designed for mains AC will be suboptimal, as Rds[on] typically increases with Vds[max]).

And you typically don't even need a "module", a bare MOSFET is fine provided that the control voltage is relative to one side of the switch and within range (i.e. enough to turn it on but not exceeding Vgs[max]).

>>959567
>What is the best temperature for soldering basic components like LEDs and resistors.
The one that melts solder within 2 seconds on whatever joint you happen to be working on at that time.

>>959572
>>959576
Can anyone green light this design so i can start working ??

Alright will mess around with it.

>>959577

green light. go!

>>959580
Thanks ! Its a long build, so i will bug you guys a lot in the coming days )) But if I can help any other anon out, I will.

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>>959393
I suspect that your best bet is a matrix. I.e. 18 logic outputs, 8 analog inputs or 16 logic outputs, 9 analog inputs), with a thermistor across each row-column junction.

8-channel ADCs are fairly common, and you can program a PIC as a 10-channel ADC with SPI or I2C interface (or buy a pre-programmed one). Use 3-to-8 or 4-to-16 decoders for the logic side.

>>959573
Yeah, conceded. This is a large setup for research tests in a wind tunnel, though, not just a hobby build. I'm not an electrical engineer so I don't have the time or wisdom to put together things like choke circuits or other supporting hardware. That's why I'm trying to stick to prebuilt hardware that should be hard to fuck up.

>>959393
Well use a multiplexer circuit, timed in a way to send the data of say 8 of them at one time. The timing will be CRUCIAL to ensure it works well.

Yeah you can get an arduino, with a 4 to 1 or 8 to 1 decoders / demultiplexers and set them up accordingly.

It is possible. Good luck.

>>959587
>go to google
>type "24V dc solid state relay"
>behold the options

>>957161
Ignore these faggots, just plug it in straight to your 5V power source, these other replies follow norms too much.
>use multimeter
>oscilloscope
He just wants to plug a fan to a 5V power source..

>>957161
1k resistor in series with 10k pot for maximum keks

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Can this AM transmitter (picture related) have its power output amplified significantly, provided that one adds a linear amplifier?

Also, how to replace the condenser mic in this circuit with an audio jack?

>>959632
>Can this AM transmitter (picture related) have its power output amplified significantly, provided that one adds a linear amplifier?

Yes, you might need some filters too. Or AC linkage on the amp. Use a high quality audio amp maybe.


>Also, how to replace the condenser mic in this circuit with an audio jack?

Wish I could help you with it. Common sense says that if the mic and the audio jack are going to make the same sort of signal, you can just solder it in.

>>959651
>Wish I could help you with it. Common sense says that if the mic and the audio jack are going to make the same sort of signal, you can just solder it in.

Is it really that simple, though?

>>959611
> Ignore these faggots, just plug it in straight to your 5V power source, these other replies follow norms too much.
Ignore this faggot unless you want to replace your mobo. The USB spec makes it pretty damn clear that it's the device's responsibility to limit inrush current, not the port's responsibility to tolerate it.

> He just wants to plug a fan to a 5V power source..
He wants to plug it into a USB port. Not only are they far more fragile than a typical PSU, a mobo is a lot more expensive to replace than a wall wart.

He also wants to vary the speed with a pot, which isn't likely to happen.

>>959665

Electronics arent really super complicated brother. If you get a similar waveform from a mic as you get from an audio jack - replace them.

There will be filters on there, if your waveforms dont match - it will not work.

If they match - it will work.

>>959667
Motor drivers that accept a control input of 0-5V via pot aren't hard to find

>>957161
Well I wouldnt really mess with a PC USB port like that. Get a powered USB hub - the one with the power adapter - then you can fuck around with it all you want.

It would be a good idea to run it off of the mobo directly or from the SMPS.

How to wire circuits without having to rely on PCBs? What's the most accessible and common method among the beginners?

>>959353
Followup question:
Is the 5V power from the usb cable used for anything vital, or can I just leave it out? Cuz then I can just make a usb-to-5xusb data cable, since there will only be one in use at any time, no?
Or, use the other half of the switch for the 5V, but then it's getting messy.

Very basic question - I have a 60 tin / 40 lead solder wire - do i need to use ''flux'' ?? And how do you use soldering flux anyway ??

>>959674
Yeah, but he's talking about a self-contained fan assembly with 2 wires. Some of those can be driven with PWM, but you typically can't just vary the supply voltage with a pot.

>>959680
breadboard

>>959681
Whether you can leave the 5V line disconnected depends upon the device. E.g. if the USB connection is opto-coupled, it definitely won't work.

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So I just started reading make electronics by Platt and ordered the required components from china (dx.com).So I tried to short the battery via a 3A fuse, but it didn't blow. I even added 4 batteries in series and there was smoke coming out and things got really hot but the fuse didn't blow. So what the hell, did the chinks sell me 30A a fuses or something?

>>959691
>opto-coupled
You lost me. Could you give an example?

>>959721
> did the chinks sell me 30A a fuses or something?
It looks that way.

If a "3 amp" fuse blows with less than 3 amps through it, people are going to notice. But the other way around is far less obvious; how many people test their fuses?

>>959721
>buying anything from china

Generally, when choosing a resistor for very low-power uses, should one aim for ones with the lowest power dissipation?

>>959745
just use 1 meg helipots for everything, what are you, some kind of pussy?

>>959737
Some USB devices use opto-isolators on the USB connection to maintain galvanic isolation between the USB device and the PC. Although, this is more common on devices which have connectors other than the USB connector and the PSU.

In that situation, the power from the USB port is required to power the host (PC) side of the opto-isolators when the host is receiving data from the device (when it's sending, the isolators are passive, driven by the signal lines).

Another issue is that the drive may use the 5V line to detect when it's connected to the PC. If the 5V line isn't connected, it may not even enable its USB interface, even if it could physically operate without that line.

>>959745
Generally, you choose the cheapest component which satisfies all of your requirements (voltage rating, power dissipation, tolerance, temperature coefficient).

For DIY, you typically have the added requirement that the component is large enough to see without a microscope and can be positioned and soldered by hand (the absolute cheapest low-power resistors are likely to be 0201 surface-mount, which is 0.6mm x 0.3mm).

Rated power dissipation is the maximum power which a component can dissipate without failing (so all other factors being equal, higher is better). The actual power dissipation depends upon the circuit.

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Hey /ohm/ my horn isn't working in my toyota pickup. I used a multimeter and it seems every step of the way I am getting power; tested switch (also tried a different switch), relay, horn (hard wired to battery), fuse is same as hazards so thats working.... I think I'm going to give up and just rewire the horn to it's own circuit to pass inspection. Excuse my shitty MS Paint drawing but is this an acceptable circuit to wire into the truck?
captcha: pickup trucks

>tldr; can I wire this circuit to my truck without it setting on fire?

>>959765
It'll be safer to use a relay if that button is not designed to handle that much current.

Hey /ohm/, slight repost from yesterday. I'm working on a personal project that requires bluetooth. Thinking about using a nRF51 from Segger. Has anyone worked with it, if so is it easy to code for it? Any other micro suggestions? only need a few gpio pins and 2 pwm for perphs.

>>959777
>spending $40 + shipping on a microcontroller with bluetooth when you could get an arduino clone and a bluetooth module for $7, shipping included

>>959778
Well I'm also looking at a few stand alone BT modules, but can't find any that cheap. I'm good for microcontrollers, but I figured a complete dev kit with the nRF51 would be the easiest to work with.

>>959787
Search HM 10 on aliexpress.

>>959822
Mentioned this yesterday but forgot for this thread.
I've used the Ti cc2540 in my last job, I loved it, but required proprietary software to develop for it.

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Can someone take a look at my circuit and tell me if there are any problems with it?

>>959864
why did you draw such a simple circuit in such a complicated fashion?

>>959870
It was not my intention to make it look complicated.

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>>954566
Would this work?

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What kind of component is this? Seems to be some kind of temperature sensor maybe

Is it possible to make a current regulator? The lights dim and my computer shuts off when the A/C kicks on, so I want to stop the current to the A/C from spiking up.

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>>959913

>>959915
I don't think inductors work as current regulators when it comes to mains AC.

>>959918

They block AC while allowing DC to pass through.

Excuse my terrible explanation of this.

Would there be anything wrong with a setup like this?
Hurr and Durr both take 12 volts. Would there be anything wrong if the solar panel and the DC source were operating at the same time? What about if it was just one of them?

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>>959963
And of course I forgot the picture.

>>959964
>>959963

Power sources in parallel like you have right there won't add their voltages together so you should be fine.

It's only if you hook the power sources up in series that they will add voltages together.

Just search 'series vs parallel batteries' to learn more

Anyone know of a good youtube tutorial type video of using transistors as amplifiers?

Also, general uses of transistors would be nice as well.


Im trying to get better at understanding how/why transistors are used in circuits like powe4 supplies, radios, etc

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>>959765

if you're getting power all the way to the horn, then either the horn is bad, or it's not grounded.
you replacement circuit is fine.

>>959680
perfboard is the most accessible way of making permanent circuits. it's like a PCB but with wires instead of traces. see pic for extreme example.

>>959632
you can do it but you'll probably end up breaking the law. the ARRL handbook has tons of designs for wideband RF amps.

>>959864
your circuit is no good. you need to use the output wire to turn on an NPN transistor, which will dump the 18V into the bulb. putting 18V into the PIR will likely kill it.

>>959963
what happens when it's dark? the batteries dump their charge back into the solar panel. you really need to use a solar controller board unless you know what you're doing.

>>959979
http://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bipolar-junction-transistors-bjt/

Anyone buy electronic project boxes off of ebay? Been thinking about buying some, and just curious where you guys buy yours.

>http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR1.TRC0.A0.H0.Xproject+cases.TRS0&_nkw=project+cases&_sacat=0

>>960016
>not 3d printing custom cases that fit your project perfectly

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>>960016
>>960018
Oh, and Serpac will send you a free enclosure once in a while if you ask politely.

>>960018
You're doing it backwards. Always start with a case then design PCBs to fit it perfectly.

>>960018
>tfw too poor to own 3d printer.

>>959918
They work pretty much like resistors, except that they don't dissipate power (their impedance is imaginary, so voltage and current are 90 degrees out of phase).

You could use one to limit inrush current but that will also reduce the operating current to some extent, and might just stop the A/C from working altogether.

>>959963
> Would there be anything wrong with a setup like this?
Yeah, half the time the solar cell will be fed power and used as a heater.

Solar cells are normally connected to some form of switching regulator to match their output to the load.

>>959976
> Power sources in parallel like you have right there won't add their voltages together
Indeed. The source with the higher voltage will end up feeding power into the source with the lower voltage.

Which is why you don't normally connect voltage sources in parallel.

>>960002
Im an EE student, so i know how transistors work. I just want to know why they are used

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Are there any good online guides for building a tesla coil?

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>>960112
If it's your first Tesla coil build.
Try making a mini Slayer Exciter. Safer, simpler, smaller, cheaper.
Than If you get that working and feel like more build a full fledge Tesla coil

>>959905
Yes indeed, it looks like an NTC temperature sensor.

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Based eBay business sent me package of 10x BC557 Transistors that was short of one unit,
They are happy enough to send me another free 10 pack for my troubles,
Really kind of them, appreciate when business got yo back

>>960089
>Im an EE student, so i know how transistors work. I just want to know why they are used

because they perform useful functions, which make them the basis of pretty much every electronic gadget you can think of. start with a classic 6-transistor radio for example: they amplify, oscillate, mix, decode, then amplify some more so you can hear the music. every op-amp is made of transistors. every digital chip from a simple gate to an i5 CPU is all transistors. same for memories. long story short: if you want to actively manipulate electronic signals, 99% of the time you use transistors.

So I was building an amplifier circuit for a analog sensor that outputs between 0.02 V to 2.00 V.

However, the circuit i built isnt working. The output / pre-amp output is giving me a steady rise from 0V to 2V DC - without anything connected. The circuit has some resistors and a few capacitors and a LM324 IC. Whatever could be the problem ??

What should I be looking for ?? I am new to troubleshooting.

>>960148
>without anything connected
So you leave all the inputs floating and the output slowly rises from 0 to 2V and then stays there?
Without seeing your circuit, I'd say it's normal. Connect the sensors, real or dummy, first.

>>959979
>using transistors as amplifiers
Basically, assuming you're taking about a simple power amplifier, you have a large power supply and use the output transistors to let some of the higher-voltage DC out based on the input signal. More complicated designs have switching modes, or do a "push-pull" splitting between output transistors to keep them cooler, or any of a handful of other general topological layouts. Researching amplifier classes (A,B,AB,D,etc) might help.

>>960155
It only takes one o/p signal from the sensor. That is all there is in terms of sensors. If you dont plug anything in (I am using male / female couplers), the voltage on the output (which is the amplified output) goes on increasing from 0 to 2.00 V with increments of 0.01 per second.

>>960170
The funny thing is, however, if you do plug in the sensor - the trend of the output does not change at all. The output signal from the sensor itself doesnot get amplified.

>>960171
You said you're new to troubleshooting, but even then... 3 posts and no schematic and no pics of the actual implementation. How do you expect us to know what kind of circuit you really have and what you might have done wrong?

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>>960176
I cant post a picture because i dont have a camera Anon.

The circuit matches the schematic though. So its a faulty component if i am not wrong. Need help with that.

>>960180
The circuit in your picture is designed so that its output voltage is normally about 2.5V and that it'll take some time to reach that voltage after start. You can't expect it to amplify properly before reaching steady state.
If it doesn't amplify properly even after that, one obvious thing to do would be to feed the circuit from a signal generator or some other trustworthy signal source and checking the outputs of the opamps to see where the signal gets lost.

>So its a faulty component
It's much more likely that it's a design or construction error.
For example, your schematic specifies 1 milliohm resistors. If you follow the schematic blindly, the end result won't work.

>>960186
I am only learning right now. I know that this is not a perfect design. The capacitor / resistor sets act as filters here.

I am learning about all this, and over time, the design will change. Right now i want somethign that works so that i can understand how it works and how to make it better.

Do you have any idea what is the amplification factor of this circuit ??

>>960191
I think I need to check this under a scope and i just read the instruction manual to this - it says that if you dont ground it when you solder the sensor - you burn it out. And I think I did just that )))

Also thanks a BUNCH, it actually started working after reaching 2.5 V. I was giving up on this )

>>960191
The first opamp stage has a gain of 1+1M/10k and the seconds stage -1M/8.2k. In total, around -12000.

>>960200
Nice.

>>960202
>12000.
No way my multimeter could pick that up ))

Will keep you posted of the developments on this !

>>960219

if you're working with the raw output of a PIR sensor, then you can use an audio amplifier to test its function (instead of an oscilloscope) coz the output is in the audio range. you should be able to detect movement when the swooshing sound varies as you walk in front of the sensor.
amplified computer speakers should work.

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I have a 5 mm green LED that I'd like to use as a light sensor (photodiode). I measured the voltage on the terminals with a multimeter. The multimeter has input impedance of 11 MΩ. The output voltage is fairly linear up to 10000 lux, where it generates about 1.5 V.

What kind of amplifier circuit should I use to amplify and buffer this very weak signal? Can I use an ordinary op-amp such as LM2902 for this?

How to know what kind of wire I'm supposed to use for connections when wiring a circuit?
Let's say the circuit is powered by a 9V battery - what wire would be the most appropriate, then?

>>960281
Current is a more important factor.
http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

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>>960276

depends what you're doing. if you're trying to send signals across a room, then you need a high gain amp using either transistors or op-amps. you can look for circuits used in remote control receivers. these are usually finicky because of the high gains.
if you just wanna detect certain light levels, then a 339 comparator with a little bit of hysteresis should do the job.

>>960281
the best wire for electronics wiring is 24-gauge solid copper wire. it's the best coz it's what's used for house telephone lines and ethernet wiring. as such, you can often find long lengths of it in the dumpster when they build houses, or when an office changes hands. one haul from an office building lasted me over 10 years' worth of projects.

>>960287
>>960291

Let's say it's a standard 9 volt 550 mAh alkaline battery. What kind of wire would be the best to use with it for small projects?

>>960301
My favorite is stranded wire I salvage from computers at work, the kind they use for the front panel leds & buttons. If I need something a bit more sturdy I go for the PSU. Something thinner: magnet wire.

>>960281
If you are experimenting with extra low voltage then usually equipment wire is used. Because of resistive heating the size of the conductor depends on the current while the insulation thickness depends on the voltage.

The kind of wire used depends on the application. Single core wire is rigid and maintains its shape when bent which is useful for making connections on breadboards, stripboards and pcbs. Multicore wire is much more flexible and useful for connecting between boards or from boards to controls or inputs/outputs for flexibility.

Typically 1/0.6 single core (a single core of 0.6mm diameter) or 7/0.2 (7 stands of 0.2mm diameter) multi core will handle almost any normal battery project. By normal battery I mean not LiPo cells for some fucking quadcopter.

>>960291
Dumpsters are a great source of wire if you like not knowing its rated current carrying capability and prefer damaged insulation.

>>960301
mAh is not a current.

>>960306
Magnet wire is neither magnetic or attracted to magnets. It's just only real defining feature is its insulation which is a very thin layer of enamel which is why you can call it enamel coated wire because that's its name.

>>960291
24 gauge solid wire is terrible, and literally it is not legal to wire up in homes because of it's terrible current capacity (3.5A). Literally I've never seen anything more than 18 in common appliances, even lamps.

>>959632
Condenser mics require a 5V bias, they use a capacitor as an integrated pre-amp. The cap in front of the mic is to block that bias voltage. If you put in a normal audio input, it will work, but then you have to match levels. A microphone outputs shit for power, it's next to nothing. Inputting anything higher than like 10mV or less could be outside the range of the amplifier. A "Line in" jack is meant for up to around 1V, and any output from a normal audio source would be far more than 10mV.

>>960383
Small correction: A normal condenser doesn't have a pre-amp built in, an electret condenser does. Both of them need the bias anyway.

>>956940
>>956938
>>958677
You can buy a commutator cleaning stick. They won't help with extreme sparking cause by gauges or burnt brushes, but they polish just fine. Literally this stuff is in every vacuum cleaner, and many other motors powered by AC.

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>>958885
I have a DSO 112. It's good for examining things, but is 1) single channel and 2) uses a serial-USB to encode data, so you need weird software to decode the usb connection. It actually really pisses me off because I can't seem to find data on decoding the USB signal, which it advertises in theory do a live mode with. Battery is good to, and is detachable if you wanted to just fix the supply.

Pic is the output from my USB sound card, showing the fastest transition rate. Also shows the gathering data.

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>>954566
>need microphone array for evidence purposes
>have unknown assortment of answering machine mics
>what do

>>960454
>answering machine
>microphone
?

>>960456
they have microphones so you can record your greeting.

>>960458
Are they electrets or passive? Electrets need to be powered to work.

How will you arrange them? In a sphere?

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>>960459
I dont know, they look like this. The pic is titled electret.
I probably have stuff sitting around that could make all of this work. I dont know if microphones like this typically are the exact same thing or if the specs vary allot

>>960463
are they electrets?
>i don't know, they look like this
>electret_condenser_microphone_capsules.jpg
higher diameter electrets are more sensitive than lower diameter ones, so if you want to pick up quiet shit ditch the tiny ones.

>>960464
>they look like this. The pic is titled electret.
You didn't have an opportunity to make me sound stupid because I already pointed out the pic said electret. Just because its in the same package doesn't mean its the same thing.
I said I don't know because I don't know if this package is unique to these types of mics. Just look at transistors, just because it looks like 'A' doesn't mean its not 'P'.

Theyre all the the same size, Should I assume voltage is the same on all of them?
Should I use an inline amp or will a recording device be able to adapt to having more than one mic?

>>960471
>Theyre all the the same size, Should I assume voltage is the same on all of them?
yes

>Should I use an inline amp or will a recording device be able to adapt to having more than one mic?
if you have them hooked up the way your image suggests, you'll only have two wires total, which equals one input. i believe everything they "hear" will be averaged out by the time it reaches the recorder. It would be mono though. If that's okay with you, you could wire them directly to a 3.5mm plug AFAIK

>>960478
Yea, mono is fine.
Are you saying this wont increase the amount of sounds I can pick up?
I planned to wire them up to a 3.5 mm jack and just record on the pc.

>>960479
>Are you saying this wont increase the amount of sounds I can pick up?
depends on how they're laid out. if you have them arranged in a sphere, that would be mono, but it would pick up sound in all directions.

>>960480
Id lay them out facing the same direction. I have 5 right now, I'm sure I have another 5 laying around somewhere else.
My idea is to have a plate of mics so that I can record sounds that are normally loud to a human but don't get picked up on a normal microphone.

>>959976
>>960002
>>960065
>>960068
Is there a simple way to make an automatic cutoff that will disconnect the solar panel when its output is less than that of the battery, or would I be better off buying one? This should only drain about 2 amps, so it doesn't have to be all that robust.

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quick question anyone know how to check capacitors? already looked into it and found out about esr meters
>pic related
but from there on everything just looks so old its like some abandoned corner of the web or chinese
any suggestions on a good esr meter or a better method to test if a caps failing or not.