/ohm/ - electronics general

previous thread >>1115120
maxed out

do any of the modern pcb programs let you just lay out a board without having to define components and make a schematic first?

>>1125247

of course. that's their main function. auto-routing from a schematic is just a frivolous extra.

Entirely off topic

But is there software for mechanical systems? I've been on a binge looking up gears and wood projects and I'd like something to play with besides a bike and Legos

Hey /ohm/

My stepper motor gets really hot, hot enough that I can't touch it for longer than 2-3 seconds. I limited the current just so the motor won't whine in static mode, full step.

If I go to microstepping I loose steps or it won't move. Not sure if this is because of too much torque or not enough current. I don't really care that much though, full step is precise enough for now. I only care about not damaging the motor with the heat.

I did surround the motor with a wooden casing, but the bottom is open and the wood only touches the top face of the motor. Maybe this causes the heat to build up?

Is there someone who can help me? Or should I post this in /3dpg/?

>>1125294
bump for answer to this question

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>>1125381
Instead of bumping your post that's in the wrong thread, why not ask your question in a more appropriate thread.
This is electrical. These are mechanical:
>>1116656
>>1124410

And since you're such an impatient little bitch, ask in both.

>>1125311

does it get hot when idling or only when stepping.

Was looking for a good electronics repair kit, thought about picking this up but I am a bit apprehensive.
https://www.amazon.com/dp/B01E4C67Q0?th=1
Anyone have reccomendations on a good tool kit?

>>1125395
idling also

I want to get the direct analog output from a barcode scanner, such that when the laser hits a black area, it outputs (for example) 3.55v, and when it hits a white area, it hits 2.5-3v

These voltages aren't required, just an example.

Do they make these? Or do I need to build my own using a laser CCD?

>>1125473
It's probably drawing current constantly.

A Google search for " idle current on stepper motor " gets LOTS of hits for overheating.
Reading some of those may point you to a solution while you're waiting here.

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>>1125527
1. Get some old barcode wand requiring you to swipe the barcode.
2. Get the signal out from the photodetector amp or the photodetector itself.

Or make your own wand based on a reflection sensor. There are special components for barcode readers like
http://www.ebay.com/itm/1PC-HBCS-1100-Encapsulation-High-Resolution-Optical-Reflective-Sensor-/272156482039
If that's too expensive, you could try using an ordinary photodiode or phototransistor and a laser pointer for illumination.

>>1125556
I'm trying to figure out the geometry of the setup. I would need a mirror of some kind, and have to figure out the math of reflection against it so the beam points into a photodiode.

I thought about the barcode wand thing, but I'd be afraid that it might be a bit too hard to tinker with it without breaking it.

>>1125527
You could set this up with an arduino

I have bad neighbours that play shitty pop music from a radio, and I want to build a jammer. Legality ignored. I know I can just amplify a MHz signal at the carrier frequency (driven LC circuit) of their radio station, and it should decrease their volume (gain?) by a factor of the relative strength of my carrier wave, assuming that's how FM works. But can I buy MHz opamps with enough power output to jam? Digikey/Mouser gives me 35 mA max output for a 3GHz GBP.

>>1125294
>>1125381
mechanical engineer here, i can't tell if you're asking about CAD/FEA or a multisim style interactive simulator. if you want the latter then your best bet is fucking garry's mod because there's nothing professional for it that i'm aware of. if you're asking about a proper dynamics simulator then you can pirate ANSYS but you'll slit your wrists long before you learn how to configure it.

>>1125606
use a very directional antenna
attach output of jammer directly to antenna
(no cables wires from jammer to antenna)
point antenna directly at their receiver

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Is the town of "Samsung" in Korea named after Samsung or is Samsung named after this town

test

>>1125721
equipment

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/diy/, I'm trying to make pic related work; for now let's say I'm using the killswitch (norm. open).
The button doesn't kill the signal, only diminishes it. I can still hear the signal coming through albeit at a lower volume.
I thought it was my amp boosting the signal but the same thing happened with a passive set of headphones.
I've also ruled out the button itself as the problem. I used jumpers to test this circuit out and they seemed okay too since obviously there was connectivity.
Another thought I had was putting a resistor before the button, but isn't the point to create the path of least resistance by shorting hot to ground?

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>>1125722
kek

>>1125723
I'd like to say that the switch doesn't seperate its contacts enough and you're hearing the signal through the stray capacitance of the switch, but that's probably wrong. Remove the button and push the wires together to see if you get the same effect. The button shown is the momentary part, what are you using to toggle between NC and NO? A complete diagram would help. If you're sinking the signal to ground to kill it, then you might run into the problem go having enough resistance between hot and ground that some of the signal still reaches the amp/headphones. Try using thicker wires and checking the connections with a multimeter for extra resistance.

>>1125636
That's what I planned on doing, but my question was about how to amplify the signal (how to drive the LC circuit), and how an FM carrier frequency works. I know each reciever must have some way of actively modulating voltage to get the same volume at 10m from the antenna or 10km from it, I'm assuming that this is done by receiving the carrier frequency and running it's amplitude through some sort of inverse voltage multiplier and using it to amplify the audio, but I don't know.

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>>1125728
I have eliminated the button altogether, same results (see pic, I'm assuming you mean short it like with the purple wire?).

>>1125729
FM radio doesn't rely on the amplitude of the signal at all. high and low levels are differentiated by fine frequency adjustments within a tight band. there's no transmitter feedback necessary in that regard. rf amplifiers can be found on digikey under the category of "rf amplifiers". you don't need the flexibility of an op amp here.

i'm not an rf expert so take it with a grain of salt.

>>1125732
Thanks for the RF amplifiers tip, wouldn't have found it without you. And I'm referring to the amplitude of the carrier frequency that stays as a sinusoidal 98.2MHz or whatever the radio station is at. Without reading this I can't see how your radio speakers don't explode when you walk close to a broadcast tower.

>>1125730
Oh those sockets are one for IN one for OUT. I guess it's for an instrument because it's mono? Anyway, your original post implied that you wanted to switch between having a momentary kill button and a momentary on button, this toggle switch isn't in the original diagram. Now that I understand your original circuit your button does short the lie to ground. There will be some slightly significant resistance in the switch or your soldering, so if you put the switch between the HOT of one and the HOT of the other, it will just break the signal instead of grounding it. This will swap the circuit to normally open though. I'm not sure how an instrument will react to this, but it won't do anything bad. If you have a SPDT switch, you could switch between shorting it to ground and sending it through.

>>1125746
radio signals couple extremely poorly no matter what, so while they vary over a broad range you're always looking at very small induced voltages (microvolts) on the receiver antenna. hopefully someone will correct me if i'm wrong.

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>>1125746
I should have clarified: Yes, I ultimately want to toggle between mom. kill and mom. on.
I was running into the signal bleeding problem before I got to the stage of implementing the toggle switch e.g. the first post was assuming there was only one, normally open button.
In regards to placing the switch between the two hots, it pic related what you're getting at? I've also done that but I've needed to have the ground break as well e.g. with a DPDT, to avoid ground hum.
What bugs me is, I got the original schematic working briefly, then it just didn't work. I was kind of hoping it would work so I could avoid buying new buttons though I suppose I'm running scarce on the ones I have now anyways.
Also, not sure what you mean by the SPDT switchign between ground shorting and sending through.

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>>1125749
As a physics student I don't think that makes sense, but I still don't know.

>>1125758
First thing's first, troubleshoot your circuit until you understand why it stopped working. Make sure you didn't break one of your appliances. Pic related displays what my circuit design is, though the short to ground might still not be a perfect idea if there's any capacitance around. Try soldering each arrangement the setup could be in without the button and switch before you have to buy them to make sure they work as intended, especially if you're far from an IRL component shop.

>>1125758

it's super weird that you're getting sound across a short circuit. presumably your source has a low impedance. you can increase it by putting a small resistor in series with the input. 10 to 100 ohms ought to silence it.

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I misclicked and ordered 15pF instead of 5pF. What is my best bet for geting the Microcontroller to "sort of run"?
>Just put in 15pF It'll be fine
>Just leave them out
>Build some wierd abortion of 3 15pF caps in series
>Try to find 2 5pF caps in random junk laying around

>>1125859
I'd go with the abortion if you have enough

>>1125859
oh for a micro 15pf will probably run fine. You will only pull the crystal to a slightly different frequency.
Otherwise do the junkbin approach.

i just got an arduino uno r3 and want to build a cnc pcb plotter, but since im a complete noob could someone spoonfeed me a decent documented budget project for it?
t-thanks

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Can anyone help me understand why this common emitter amplifier isn't working?

I thought replacing Re with a current source, in this case a current mirror, was supposed to improve linearity or something but now I don't get any output.

Also, how do I calculate input impedance with a current mirror instead of emitter resistor? The Zin = β*Re formula doesn't work for that.

There was this website where you could enter in your requirements for a chip. Logic gate, transistor, etc., then you could type in the voltage requirements/range, amperage, etc. and it would return a list of parts that fit your requirements.

Does anyone know it?

>>1125961
Maybe your simulator or at least your transistor model is poop. Other than that:
- The impedance of your current source is determined mainly by the Early effect (which isn't always modeled).
- You should to reduce R1 to account the voltage losses in Q1 + the wanted output amplitude.
- You can expect very low gain, like basic G = Rc/Re suggests.

>>1125980
Any decent component maker like Texas Instruments or Murata provides a parametric search. The bigger retailers like Digi-Key, Mouser and Farnell also provide parametric searches.

>>1125961
sometimes you need to manually enter in the transistor properties

How do I get into electronics jobs like soldering/assembly/testing etc?

Seems to the same old 'Need experience to get a job and need a job to get experience'

Qualifications like IPC610 cost about £700 so fuck that.

I've applied for a local one which doesn't need experience as training will be provided but I doubt I'll get an interview let alone the job.

rosin core leaded, or separate leaded and a tub of flux?
I'm soldering a MicroUSB port on a tablet, nothing huge.

>>1126074
Rosin core and preferably extra flux. If you get flux to the connector's inside contacts, you might need to wash it with alcohol.

>>1126069
Dunno about what you exactly want, but at least the local companies here offering the mind numbing variation of the theme require very little experience or skill.

>>1126075
Is the work that mind numbing?

Looking for jobs in electronics here they all need experience and qualifications.

>>1126075
sorted, thanks pal

>>1126076
Mind numbing variety: there's a pile of machine-assembled PCBs, enclosures and preassembled cables next to you. You take one PCB and one cable and solder the cable to the PCB. Then you put the PCB to its enclosure and screw it closed.
Then you take the next PCB, cable and enclosure. Again and again, day after day.

Yeah, that kind of work does not require qualifications. It is available on major assembly houses here and they're constantly hiring.

>>1126080
Is there any job progression or is that it?

>>1126081
you can't become an engineer without a degree anymore and the notion of dumb labor positions getting moved to management is entirely wrong because you never get an opportunity to show skills outside your very narrow field of work.

>>1126083
Where do you work?

>>1126092
i'm an engineer but i don't care to specify where. one of my coworkers actually doesn't have a degree but he's effectively grandfathered in and can't easily find a job anywhere else.

>>1126097
Just when I got my hopes up about something I might like to go into ;_;

What's a good resource if I wanted to make a lifepo4 battery charging pack that could charge a 45W laptop in addition to phones and stuff?

Could other lithium ion chemistries also work? It looks like a lot of the "jumper" boxes use shitty exploding li-poly cells.

The quality stuff that's reasonably priced all looks to be 5V and less than 4A from all ports. I'd be targeting 15V and 3A, hopefully with an option for the common USB 5V/2.1A, and hopefully without costing too much.

>>1126099
A technician that does more than soldering things together is probably going to need a 2-year degree. But if you need a job anyway, just go try the mind-numbing job and see if there's any paths to advancement.

>>1125799
>>1125786
>>1125730
>>1125723
OP killswitch guy here:
I tried the resistor inseries with the input, which worked but at the cost of volume.
I noticed that when Prototyped the first setup (button across output) it worked fine with just testing cables; the problems start when an actual device is plugged into the input.
For reference, Im big into circuit bending so for testing I ran a sound effects-type toy running on two AAs to the input, as well as trying a guitar pedal at 9v. Both had the same problem with the signal still bleeding through with the killswitch engaged.
If it's an impedance problem I'm all ears to solutions since frankly I was taught very little about it.

>>1126136
Can you chat and listen to music whilst your soldering?

>>1125961
If the emitter current is constant, the collector current is constant and you will not get any gain at all in response to a signal at the base. In other words, if the emitter current is constant, the voltage at the collector will also be constant -> no amplification. In a sense it IS extremely linear.

>>1126139
tried running a mixer, path goes:

bent toy -> killswitch prototype -> mixer -> amp

What I found was kind of spoopy: even when I had broke all connections from the toy to the mixer (meaning there's just two cables unconnected, one from the toy, one going into the mixer) I could still pick up a faint signal even at relatively low volume settings on the mixer. Granted, the mixer usually didn't register these levels above -20 db. I think the alligator cables I'm using to prototype are acting as antennae since the close they are to the toy's output, the more they pick up.
At this point, the most effective option I've found is putting a SPDT between the hot leads for in and output; the first killswitch schematic is nowhere near as effective.

How hard would it be to build this

https://en.wikipedia.org/wiki/Chua's_circuit

>>1126165
Not very. Your article has a link to a real world implementation.

casual here. I recently unboxed a fluke multimeter that hasnt been used in over 10 years and it still has power, but when nothing is connected it reads sporadic and random voltages. Also, resistance reads OL at all times. Do you guys think a simple battery or fuse replacement could fix this before I waste a trip to the hardware store?

>>1126141
>Can you chat and listen to music whilst your soldering?

you pretty much have to to stay sane. i remember at one job where the assembly fuckers would beg the manager for a 1-hour cleanup job of the work area (at the end of the day) just to break the monotony.

>>1126165
There are lots of writeups out there. I even bought the parts once but never put the damn thing together, I wonder where they went.

>>1126195
Ten years? Battery.

>>1126195

definitely replace the battery

if that doesn't work then crack it open and look for damage

>>1126195

more than likely, the range switch is all oxidized so youre getting no contact. youll need to disassemble it and rub all the contact points with an eraser.

>>1126080
What's it like living in China?

>>1126150
If you're into music and electronic gizmos, try making an elektrosluch:
http://makezine.com/projects/weekend-project-sample-weird-sounds-electromagnetic-fields/
It will let you listen to audio-frequency RF floating about, and from having made one and using a 5MΩ resistor to maximise the gain, I can tell you you won't be picking up any wireless RF without at least some decent inductors. Unless your amp has a godly gain, of course.

I'd first test your circuit until it works with your headphones, then worry about any amplified small signals. If you could provide a diagram of your ghost sound setup perhaps someone here could debug it, photos also help.

>>1126224
Tbt I do a boring job at the moment but being able to chat makes a massive difference.

I've been looking at jobs more and many of the high end testing jobs don't need a degree just lots of experience, the lower end testing jobs sound quite varied too.

Maybe I'll try and get an assembly job and try and progress from there.

What's up /ohm/? You guys have set me on the right path before. I have a question about a guitar effect, im trying to build a circuit with a similar effect without knowing anything about it. The big holdup is that it uses a microcontroller which I know nothing about. Ive found some resources on them, but none focusing on audio/dsp. Im sure ill be able to find something and with a lot of reading, trial and error ill figure it out. im just trying to figure out what chip this guy used.

>It uses an 8 bit MCU which reads the input signal through the internal ADC and it outputs the signal as a square wave. It also runs some additional code to output square waves 1 & 2 octaves below your input signal.

For those that don't know music, 1 and 2 octaves lower would be a half and a quarter of the original frequency originally. So if the original pitch was 440hz the others will be 220hz and 110hz. I spent about 2 hours on google last night trying to find something but i couldnt even find any 8 bit chips.

Tl;dr
Trying to find an 8 bit audio MCU with an internal ADC capable of converting an input signal into a square wave and the ouputting the orginal frequency, as well as halving and quartering it.

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>>1126379
Might be easier to think "time" rather than "frequency" (TIME = 1/FREQUENCY)

>8 bit MCU
More bits is fine. I think speed would be more important.
>input signal through the internal ADC
Any uC with an ADC like Arduino or MSP430 would work.
>outputs the signal as a square wave
that's just digital output

I think the hardest part would be measuring the frequency.
You'd sample the ADC and store results, but not sure on the algorythm to detect the distance between cycles of a sin wave.
Probably find the peaks or zero-crossing.
Might be easier to amplify the signal to a clipped semi-square wave and just measure the on+off time through a digital pin rather than an analog one. IDK

The rest wouldn't be too bad to code I don't think.
-calculate the "on time" of the input frequency (1/F)2
-Using the timer, set up a delay, calling an interrupt every 1/4 of the input "on" time
-in the interrupt function keep a count of calls with a static or global variable
toggle the F/4 pin every interrupt
toggle the F/2 pin every other interrupt
toggle the F/1 pin every 4 interrupts

Maybe you can help me with something:
As you said, a lower octave is 1/2 the frequency.
Is there a formula to calculate note frequencies without a list?
I mean if note A6 is 1760Hz, is there a formula to calculate the frequency of B6?

>>1125758
If your goal is to have no signal, you can get a ganged switch that will break the + and - sides of the signal with one throw.. Look up DPST switches on Digikey.

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>>1126379
how pure will the input signal be? if it's dirty and the dominant frequency doesn't stand out that much then you're entering FFT territory. if you want all frequencies downshifted then you can't do that on a squarewave output.

if your input frequency is moderately clean then you should consider a dumb solution like pic related.

>>1126379
> converting an input signal into a square wave and the ouputting the orginal frequency, as well as halving and quartering it.

>>1126427
Seems like you're really overthinking it. An algorithm to do what OP wants would be

Boolean OldState,PresentState; //use to detect transition;
unsigned char counter,// use for frequency division
ADC_high, //use to auto-level the transitionpoint
ADC_low,
ADC_value;
while(1){

//calibrate transition point
ADC_value = Read(ADC);
if(ADC_value > ADC_high)
ADC_high = ADC_value ;
else
ADC_high--; //high creeps down

if(ADC_value < ADC_low)
ADC_low = ADC_value ;
else
ADC_low++; //low creeps up


PresentState = ADC_value > ADC_low+ADC_high/2; //is the input above or below the halfway point between its max and min values

if(OldState != PresentState){ //detect transition;
OldState = PresentState;
counter++;
}

if(I_Want_Input_As_Square_Wave){
DigiitalOutputPin = PresentState;
}
if(I_Want_Input_As_Square_Wave_1Octave_Lower){
DigiitalOutputPin = counter & 2; //2=0B00000010;
}

if(I_Want_Input_As_Square_Wave_2Octave_Lower){
DigiitalOutputPin = counter&4;//4=0B00000100;
}
}

So I'm thinking about making a TV stand that will house a number of retro consoles. To reduce cord clutter, I'm thinking of integrating a DC power rail into it and I want to have a clean and efficient power signal.
Switching regulators get you an efficient conversion, but can be noisy.
Linear regulators get you very clean signals but is rather inefficient.
Question is, can I feed power from a switching regulator into a linear one to get a clean and efficient signal or should I just make a filter bank for a switching power supply?

>>1126742
>Question is, can I feed power from a switching regulator into a linear one

youd get the worst of both worlds. the switching noise would still be there, just attenuated a bit, and the heat from the linear regulatror would still be present irrespective of the source.

best bet would be all switching, coz consoles dont much care, as theyre also quite noisy internally.

anyone here have experience with altium? for some reason the designators aren't incrementing in the schematic.

>>1126742
linear postregulators will attenuate ripple pretty well as long as it's <100khz and you follow the datasheet. chinese offline smps won't generally be over 100khz but if you find one that is you're better off adding a passive filter.

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Anyone here familiar with Ti C2000 MCUs? I'm trying to find the best MCU for high performance FOC motor control. The C2000 models have the best PWM of the MCUs I have looked at and delta-sigma support which I also need. Ti claims their latest high end C2000 products can run FOC code on dedicated hardware and theoretically outperform ARM M7 for motor control but I haven't been able to find any direct comparisons. However the embedded programmers I talked to seem to hate the C2000 and claim it's too much hassle to use them. I have been looking for an ARM M7 alternative but nothing seems to have high res PWM and delta-sigma support on the same chip.

>>1126514
>Seems like you're really overthinking it.
Yea, I'd just been generating audio. Didn't occur to me that all output times are lower than the input one.

I like how you calibrated.

>>1126742

just use a computer power supply and be done with it

I have to take a class about autocad

Not really interested in mechanical faggotry though

In this class they basically just let us do whatever we want with their autodesk student licenses so I should probably start a project

what should I do?

>>1127155
model the unigraphics logo. maybe they'll take the hint and buy a program that isn't autodesk trash.

>>1126872
I'd avoid anything with a proprietary toolchain, but that's just me. If it really has the features you need then you'll have to bite the bullet.

>>1126742

Yes you can feed the output of a switching power supply into a linear power supply.

The chap over at the EEblog Youtube channel built a battery powered variable power supply with a buck boost switching converter that feeds out to a linear chip. The advantage is that the power dissipation in the linear is minimized by tracking the switching reg to just a couple of volts over the final output.

I enjoy his work very much, but I don't love the accent. :)

Serious overkill for consoles, fwiw.

I looked at some books on electronics today. They were like $250 for three of them. They weren't even printed on vellum, illuminated and bound with leather.

>>1127357
books are free, anon

>>1127358
They should be.

>>1127360
they should be and they are

>>1126379
The easiest analog way to do it would be the "U-Boat", by "valvewizard" aka Merlin. The trick guitar octave down is that it's really hard to get a clean enough signal. The 2nd harmonic is generally pretty strong with guitar so you end up having multiple zero-crossings per period of the fundamental frequency. The trick with the U-Boat is that it uses window comparators referenced to the input signal so you get better tracking of the fundamental frequency.

>>1125859
Capacitors in series drops the capacitance like resistors in parallel. 2 in series = 1/2 the capacitance.

>>1126099
An AS in Engineering (and Applied Science) can be gotten for free if it's from a CC, though it'd take two years. I was asked about a 1+ year full-time machine operator, with training, but I was already in a semester for my BS.

>>1126742
Just use a bigger capacitor you twit. Usually the "specified" capacitors get within like +/-50mv, which is way better than any old rectifier-and-caps would do (they literally cannot provide better regulation than even the cheapest switcher you can buy). Increase the filter cap by like 10x and you'd have like +/-10mv at most.

>>1126379
http://www.ece.rochester.edu/projects/laics/ilfd.html

Injection-locked divider could work.

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Beginner here
I've built a three gate RC oscillator from a 74AHC04 with the capacitor interchangeable to test random capacitors as a learning experience.

I've got an Arduino set up reading the frequency (perhaps a capacitance meter build?) but I have no clue how to solve for the capacitance.

I've googled like a mad man but I can only find ready made calculators for it or how to calculate the frequency from the resistor(s) and the capacitor but not capacitor from frequency and resistor, and I am horribad at math.

Anyone that can point me in the right direction, please?

not sure if this is the place to ask, but, is there a software that help with the layout of components in a breadboard?
something like, I make the circuit and the software puts in in the software in hte best way possible?

>>1127864

there is no formula. the frequency changes with supply voltage and from one chip to the next. if you use a chip from a diff manufacturer it, you can get a 300% difference.

so you're climbing up the wrong tree with this idea.

>>1127869

you want an efficient placement on a breadboard? well, you cant have it. breadboards are naturally inefficient. if, by chance, you meant a PCB, then the answer is a PCB with auto-router software. these are listed in 1st post of this thread.

>>1127875
I mean breadboard, I'm really bad at it placing the components and usually have to rebuild, I'll have to practice more I guess

>>1127878

yeah dude, practice makes perfection. e.g: i didnt get good at mastubation until age 5.

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>>1127864
here you go anon:

>>1127882
also the numbers were taken from a random 74ahc04 datasheet by didoes inc. not sure what model you're using, but you can change the numbers to fit.

>>1127869
For breadboarding I usually layout the components as close to the schematic as I can.

>>1127882

the numbers 1.65 and 3.85 are minimuns and maximums, respectively. note that there's no entry for a typical value, because there isnt one.

so your calculations are useless as they vary from chip to chip. you might as well figure it out it by trial and error.

>>1127900
Sigh...
Literally just said I took a random datasheet and used its numbers and he should replace it with the one he uses.
Second, using the min and max is the only way you can make some analysis to this kind of circuit. If you try to take into account how statistically the thresholds change by temperature for example it will be much easier to kill yourself.
Third, he's making a fucking circuit to test caps with a piece of shit arduino, he's not making an airborne fuel gauge so stop being a dick, this is /diy/, not /pol/.

>>1127945
let me tell you about the electric jew

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I'm creating a custom case from aluminium to house a ps4 pro with my own cooling solution.

The main board has extensive emi shielding but they made an opening for the wifi card and it also has external aerials that extend around inside the plastic shell. Will it harm the wireless performance if all of this is enclosed within an aluminium case?

The case will be roughly 30cm x 30cm x 10cm from 12 gague (~2mm thick) aluminium

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>>1127960
There's 3 aerials (2x wifi and BT) and they terminate in these little metal pieces. If I screw these into the case will it allow them to pick up signals from outside, or maybe if I solder the ends of the aerials directly onto the case?
Or would having 3 aerials all coupled onto the case cause them to interfere with each other?

Sorry for all the questions, I know nothing about wireless tech.

>>1127962
Dont contact the Antenna to anything else,
you will detune them and get worse performance, and worstcase the wont work anymore at all

>>1127960

a metal enclosure acts like a faraday cage and will kill, or seriously harm, any radio signal trying to get in or out. touching the antennas to metal is out of the question, as the other dude said. the best solution is to disconnect the internal antennas and add external ones. you can get an old router for $4 at the thrift store and salvage the antenna, connector, and internal cable. hopefully the PCB connector matches.

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>>1127945

your calculations are worthless, and there's no point defending them. if you wanted to make a meaningful contribution, you should've at least steered the noob towards a 555 oscillator coz the RC calculations are standard across various manufacturer's and at various voltages and temps.

Why does this IC have such strange supply voltages?

http://electro-music.com/forum/phpbb-files/mm5871_228.pdf

VGG: min -33v max .3v
VDD: min -18v max .3v

"input voltage" is a different category: min -18v max .3v

>>1128031
because its a weird analog/digital combo made with p-mosfets in the 70's-80's?

>>1128034

How do I go about making a powersupply for it?

>>1128036
use a MC34063 in an inverting configuration to get the voltages you need

>>1127963
>>1127998
thanks for the advice, I actually have a couple of old routers laying around somewhere.

And it's okay for the nic itself to be inside the case? They seemed to make a point of having it outside the emi shielding (my first pic)

>>1128036
Depends on what voltages you have available and what you consider convenient. One option would be to use, say, 30V transformer + rectifier and then zener regulators to produce the two negative voltages. That would be period-correct. A more modern option would be to use an inverting switcher for -27V and maybe a linear regulator for the -14V power. This assumes you have some low voltage positive supply available and that you have some use for the positive voltage, too.

Considering how fucking simple that IC is (it won't produce drum sounds itself)... Have you considered producing the patterns by something bit more modern?

>>1128041

No I have this chip and I want to use it just for the sake of using it

Is the voltage drop of a diode-connected BJT less than that of a silicon diode? What about MOSFETs?

>>1128229
Use a Schottky diode instead, Anon.

>>1128229
Silicon BJT = silicon diode drop. MOSFETs work in a totally different way.

>>1128376

The body diode in a standard MOSFET is a silicon diode.

>>1128229
BJT: slightly, since you get the transistor action in addition to the basic diode action.
MOSFET: if you can drive the gate properly, you'll get an active or synchronous rectifier, which will have low voltage drop. If you just connect the gate to the drain, generally not, at least not with normal fets.

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Hey guys I just bought an ebay special soldering iron and was just wondering what the fuck this thing is?

>>1128409

the heating element

>>1128409
That doesn't look bad, how much?

>>1128372
i'm not trying to get a "better" diode, I just need a range of voltage drops. I laready have silicon, schottky, germanium, and IR LEDs

>>1128435
Sounds like you're trying to make rules of thumb of something which is basically one huge "it depends".

>>1128438
I know "voltage drop" is only a simplification of the fact that diodes have distinct I-V curves. I'm trying to make a diode clipping circuit that acts as a compressor or expander by selecting different types of diodes with a CD4066 depending on the input level. Schottky and germanium diodes begin to clip at about the same level, then I have a gap between those and regular Si, and an even bigger gap between that and an IR LED. I'm trying to find devices to fill in the gaps.

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>>1128602
Use whatever diodes are convenient and bias their other ends suitably. Amplify signal before clipping, if needed. You can also use ideal diodes if needed. This method allows continuous adjustment of the clipping level.
Or just use some of the well known, tested circuits for compression/expansion.

To answer your actual question: different diodes have different characteristics even if they're made of same material. For example, BAY135 and BAV199 have higher voltage drops than 1N4148, even though they are all small signal silicon diodes.

>>1126872
I've worked with them before, but it was mainly for ADC capability. CCS isn't a horrible environment to work with, and the micro had a decent set of features. Nothing really stood out to me either way

>>1128422

Was around $50 australia funbux maybe $53?

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Would this work in real life?

Teacher asked us in a test to step down 35V to 5V without using IC linear regulators, voltage divider wouldn't do the trick since it had to be a regulated output, and this was the best I could come up with, I've never thought of an opamp like this, it was simulated OK but realistically though, could this much heat and general inefficiency destroy an opamp?

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>>1128693

What kind of current are you looking to get out of it? Most opamps can only source/sink a few tens of mA, max.

Make the opamp drive a transistor instead, you need more current. That offloads the heavy lifting onto a device that can handle it (with heatsinking as necessary, of course).

Also, your regulator doesn't meet requirements. It's simply acting as an amplifier for a voltage divider. Therefore, it is unregulated. You need to use something that holds a (relatively) stable voltage drop, regardless of how much current is going through it. A bandgap reference, zener diode, or even just several regular diodes in series would do.

ALSO, come the fuck on, man. Literally the first result for "opamp voltage regulator".

>>1128435
fet/igbt diodes range from .7 to 4, i'm sure there are some with less
bjts are universally .7 up to 1 at load
standard diodes are seldom outside .7-1.1
schottkies go as low as .35
LEDs vary by color, at ~1.8 for red to ~3.3 for blue and i forget what green is

diode clipping circuits are oldschool masturbatory bullshit. use op amps or literally anything else.

Where would I find good soldering practice kits, other than RadioShack, in a deadbeat suburb with age-old strips being the majority of non-residential buildings? Northern Virginia, US

I can give a specific city/town but I would really prefer not to. Just general chains or w/e would be helpful

>>1128736
i assume there's a reason, but why not just get one on amazon? you can probably get a butane at home depot but i haven't seen any bench irons there. maybe harbor freight?

>>1128737
sorry just realized you said practice kits. even my local electronics shop doesn't have those.

>>1128738
Yeah lmao, I have an iron. Haven't heard of one run with butane but I guess I'm looking for practice kits so I don't really know anything, other than ~425°C is very hot...

Thanks anyways, I figured I'd probably be choosing from the 8 different kits in RS if I didn't want to shell out extra cash for S+H.

I have acquired the led strip from a fluorescent replacement tube and want to use it as under-cabinet lighting. Trouble is its a plug and play, meaning its meant to work with a ballast and expects ~3 times mains voltage and a rather high frequency. Is it plausible to modify the circuit by replacing caps and adding a step-up converter so that it can be plugged into a wall? If so, how would one go about working out the layout of a pcb to start changing shit?

>>1125636
> very directional FM antenna
That's gonna be large.

>>1125247
I like SprintLayout for this.

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>>1125247
You might find https://github.com/boldport/pcbmode interesting.

>>1128867
No it wouldn't, you can make yagis out of tape measures

>>1128707
>oldschool masturbatory bullshit.
e x a c t l y . The circuit is a direct tube screamer ripoff except that the diodes are switched with a CD4066, and the extra circuity to control the switching. And yes, it uses op amps, but the diodes still provide the clipping voltages in the feedback loop. pic related is a preliminary sketch; I will be elaborating on the control circuitry. Possibly adding in an LFO if there's enough room on a board that will fit inside a little box.

Hipsters dig that oldschool masturbatory bullshit, though. And hipsters will buy that shit up.

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Who /ESP6266/ here?

I just recently started playing around with one and it's pretty exciting.

>>1128818
figure out how the LEDs are wired (# of series / parallel combinations)

i'd cut the traces into something more manageable ( like a few parallel strings of 12V )

>>1129136
There's a dude on YouTube I watch who uses these all the time. I just bought some the other day for my home automation project. Gonna start with opening/closing my windows through my phone.

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>>1129128
forgot to attach

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I need to make a power supply that will provide constant current to pic related.

What do I do?

>>1129159
How are you doing it?
I started developing in C using the manufacturer's SDK, but got discouraged because of sparse/wrong documentation and went to NodeMCU.
Or are you using it with an arduino?

>>1129227
I'm basically just doing what this guy did.

https://youtu.be/pWo-ErpVZC4

>>1128701
Are you retarded? It was an assignment for a class to change voltage. He's literally not using it for anything, nor will he ever construct it. An op-amp is literally what the teacher was asking for, unless you'd expect him to have a switched mode supply memorized.

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im making a ridiculous led light. its powered by 125vac being rectified to 175vdc across 6 100 watt led cobs in series with 3 rows of 6 in parallel. i need a way to deplete the capacitors when i turn the light off because while the cobs can drain the capacitors down to like 100 volts, after that it drops below their forward current and does not drain the caps anymore and i dont want all of that power being stored for no reason. i need a good way to slowly drain the caps when the power is shut off that doesnt interfere with the lights while its on nor involves a snap discharge or anything like that, i want to actually make this into a usable light on a stand so i want to avoid having a loud explosion every time i turn the light off.

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>>1129269
simple diagram of the circuit, its literally just wall to bridge to switch to lights

>>1129220
If you're trying to do ac to dc conversion, look into a full bridge rectifier. To modify the output voltage, use a transformer.

>>1129269
>>1129272
No series resistors in the strands???

Also, put a 1Meg or similar high resistance resistor in parallel to the caps.

>>1129269
just put a high val/watt resistor across the array so idle dissipation is low

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>>1129269
>>1129272

You could add a resistor of a mega ohm or so across the caps. This will discharge them after about an hour and not waste enough energy to worry about during normal operation. That's how CRT monitors and pre-LED camera flashes protected repairmen from shocks.

If you want fast discharge that doesn't waste power turn the unit off and on with an SPDT switch like pic related. The "off" position can be used to connect the caps to a discharge resistor.

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>>1129220
If you want constant current at a constant voltage, your circuit should only draw that constant current when provided with the correct voltage(s). Except in the case of non-Ohmic resistors, which LEDs happen to be. They'll still increase their current when you increase the voltage across them, but the current increase will be much greater than an Ohmic resistor would have, as they have a hyperbolic curve rather than a liner one. Long story short, you need something to limit current, or else have a very precise voltage source that can account for temperature changes in the LEDs. It's not that big a deal if you don't do this, I've got a 3V coin cell powering a 3V LED and it works fine, but in extreme conditions your LEDs might not last as long. If your LED chip (assuming you don't own a massive 32V LED) already has resistors in there, you're in luck. If not, have fun searching for an online tool to let you calculate the correct resistor to put in series with your LED bank. The correct voltage drop and current drain across an LED is pretty much determined solely by its colour, so it shouldn't be too hard to find the resistor value, multiply it by the amount of LEDs in series (probably), see what power value it needs to be through P = I^2*R = 0.995^2*R, and buy it.

In contrast, the fan is fuck easy to run, just put the right voltage across it and it will be fine. You can experiment with putting potentiometers (variable resistors) going to both the fan and the LED bank to dim them assuming they can handle the power (max power through a pot is when its resistance is equal to that of what it's in series with). Chances are, it won't work with the LED bank, but they're pretty iffy with pots anyway, what with the nonlinear effective resistance curve and all that.

Cont.

>>1129297
You can buy transformers with a 110>12V easily, and probably 110>32V easily too, but you might have to search around to get a multi-tap/multi-secondary transformer with the right coils. Also ask someone else if you'll get the rectified DC value as the peak-to-peak/peak value of the 32/16VAC, because that would be bad. Test all your voltages with a multimeter before you plug your stuff into them, both the AC and DC sides. Buying a prewound transformer is by bar the better option; winding your own is a hell of a task. I'm 1/4 of my way through a 200ft roll of magnet wire on my quest to produce radio pollution by transmitting audio as RF, and I'm not making much progress. If you really want to remove the hassle you could buy a small 12V power brick and somehow buy a 32V power brick, but that removes all the fun. I can only guess that you're making a soldering station lamp; I also made one of those but with a 240VAC fan and light bulb I salvaged out of a microwave, certainly made it easier, though I'll be the first to admit I wired the hot to the outer case of the bulb and not the inner pin. I made my own foot pedal out of plywood and a microswitch from the microwave door, which helped. Good luck in spending under $40 getting parts, by the way.

>>1129235

According to that post, it's an assignment to get a REGULATED output from an unregulated input, and, given that he's explicitly asking if it will work in real life, it's a reasonable assumption to assume he's supposed to actually breadboard it. He also asked if there would be issues with heat, which is going to be dependent on how much current it's passing; hence, "how much power do you need out of it?"

Somehow, I don't think I'm the retarded one here.

>>1129302

replying to troll haters is definitely a retarded thing to do.

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Hi guys can you tell me wich answer is corect ? The question is : In wich one the transzistor is polarized corectly ?

>>1129394
why in romania transistor sideways?

>>1129394
they can all be considered to be polarized correctly depending on what behavior you want

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Hello. I bought a good PSU for someone's computer, but I'm not sure if the nobreak this person uses is at least as good as the PSU. So, I'm not sure if I should plug the PSU directly on the wall socker, of on the nobreak.

What to do?

>>1129417
What do you think the matter is?

>>1129419
I need to know the UPS (nobreak) quality, but I don't know how.

>>1129421
hook it up to an oscilloscope and plot the load characteristics

>>1129422
I don't have an oscilloscope.

>>1129410
Than what's the general polarisation

>>1129426
consult your textbook

there is no general polarization

there are 4 modes a transistor can be in: reverse active, forward active, saturation, and cut-off

>>1129424
perfect time to get one then, make sure that it can handle whatever the mains voltage is where you're living

I'm curious why you think that the UPS being "worse quality" than the PSU is a concern since they do two very different things.

>>1129428
>perfect time to get one then
Too expensive.

>>1129428
>I'm curious why you think that the UPS being "worse quality" than the PSU is a concern since they do two very different things
Bad quality UPS power regulation would harm the PSU power regulation. Like a mechanical stabilizers do harm the PSU.

>>1129428
A)

1) The arrow shows the direction of a pn junction, therefore this is a pnp BJT

2) In order to use it as an amplifier, it must be in the "linear" region, which for silicon doped transistors is around 0,75 V between base and emissor.

3) Since this is a pnp, the Vbe voltage must be positive from emissor to base. (which eliminates b and c)

>>1129430
what if I don't want to use it as an amplifier?

>Vbe voltage must be positive from emissor to base
Vbe is Vb - Ve
Veb is Ve - Vb

>>1129394
If this is from some introductory book and one of the first questions, I'd say it just has a typo in it and none of the options applies.

>>1129445
I would find iB, iC, and iE for each and then explain how each configuration is valid.

>>1129394
It's 1. These anons are retarded, in answer 2 and 3 the transistor is off.

>>1129451
Off is a valid transistor configuration.

>>1129453
Which is why I said you're retarded.

>>1129275
no there didnt seem to be a need when i was testing it. what should i put in there?
>>1129276
>>1129277
how high of a wattage? it usually pulls 175v at 5a or so

I just asked this in the qtddtot, but here might be better. Is it feasible to shine a laser through an OLED screen to laser project a shape or text being displayed on said screen?

>>1129526
No. It would work to a certain extent with LCD panels, but there's a reason this projection through LCD thing isn't really used anymore.

>>1125294
try out COMSOL. I never learned how to use it but it might fit your needs

>>1129529
Would it work for simple shapes, though? I figure with a strong enough laser, I'm not trying to get multiple hues or anything.

>>1129534
comsol is mainly for fluid flow, thermodynamics, and heat transfer simulation. Not sure that is what they want

>>1129672
OLEDs? They aren't shutter-like, so no. LCDs can be made to work.
>>1125294
This isn't anything "serious", but you might find it useful nonetheless:
http://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

Is there any point in getting insulated screwdrivers or is that just for electricians?

>>1129475
>>>1129275 (You)
> no there didnt seem to be a need when i was testing it. what should i put in there?

Choose an operating point according to your datasheet. It consists of a voltage V_LED per LED and the associated current I_LED. As they are connected in series, the current within one strand is constant. Now add up the voltages of the LEDs and subtract it from the voltage V_SUP of your power supply. The value of your resistor is
R = ( V_SUP - n*V_LED) / I_LED
For the dissipated power see the following section. The problem with LEDs is that their current varies hugely with the voltage across them, which you will see in the V-I-diagram of your datasheet. The resistor limits the current. Also you could argue that you could put one resistor in series with all the strands opposed to putting one in every strand. But this is a bad idea due to variations between the actual V-I-curves of the LEDs.

>>1129475
>>>1129276
>>>1129277
>how high of a wattage? it usually pulls 175v at 5a or so

It does not depend on the current of the complete circuit, as your bleeding resistor will be in parallel. The following formulas apply:
V = R * I
P = V * I
You know the voltage and you choose a resistor of 1MR, which will dissipate
P = V * V/R = V^2 / R = 175V^2 / 1000000R = 31mW
so a 1/4W or even 1/8W Resistor is plenty. You could use 2 times 500kR to increase the airgap.

>>1126742
You're not going to have any issues with noise anyway. Everything that needs that DC power is going to be doing digital calculations.

Soldering virgin here. I'm putting a circuit I breadboarded onto this protoboard
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=217105288&uq=636225084921640533

The top side (no traces) is pretty cluttered, so I'd like to put my patch wires on the underside, meaning that they're electrically connected on the entrance side of the hole rather than the exit. How bad is this compared to putting them through the hole like my components?

Any other general tips?

Thanks.

>>1129994
broken link

soldering jumpers in upside down works fine but it's cheating

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i want to add some voltmeters and ammeters to my generator. its set up in a 2 pole hot system where the 240v plug uses 2 hots and the neutral and each set of 120v plugs each use one of the hot poles and the neutral. measuring the 120v plugs is easy enough, just do each pole to neutral. for the 240v side, do i just hook the two hot leads to the meter? and for the ammeter can i run the neutral through it so i wont need separate ones?

>>1130057
ammeter won't work like that.
it won't measure 240v loads.
also, if you think about it it won't measure correctly if you have an appliance on each phase, when the voltage reverses so does the current, so the phases are opposite so when one side is 'pushing' current the other side is 'pulling' current, some of the current will go directly from one phase to the other on each cycle and won't pass through the common neutral at all. you need to keep them separate until they are measured (or just put them on the hots).
the problem then is that you cannot separate the neutrals on the 240v socket and if you put them on the hots you will be counting the current twice!! whoops. so you might need a few more meters i guess...

>>1130060
damn guess the easiest thing to do would be a pair of 120v voltmeter and ammeter setups and just add them manually for the 240v output

>>1130138
but for just 120v the voltmeters depecited are correct and the ammeters i should do the same thing just across each hot lead instead of the neutral correct?

What's a /diy/ approved soldering station?

>>1130331
BUILD YOUR OWN

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my quick monday evening project was to build a induction heater. i was even able to heat a piece of chili with it bit above room temperature.

would not stick my finger in when its running.

>>1130493
looks good
reminded me of the one at work
the coil was copper tubing with coolant running through it

>would not stick my finger in when its running
.
The coil on that one was big enough to stick a hand through - but I didn't.
I was assured it was safe unless you had a ring or watch or maybe a metal 'splinter' you'd forgotten.

What would happen if I tied a 5V supply to the output of a digital logic IC? E.g. http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=217103685&uq=636226026372307366

Nothing, right?

Is it possible to run two different types of LEDs (3,2 V and 2V) on the same power supply by using different resistors? Its probably going to be around 70 to 100 LEDs total and i am pretty clueless on how much of them i can connect in series (the opposite of parallel). I am aware that i have to split them into strings of around 6-8.

Any helpful input? Yes its going to be a growlight. No i dont want to grow weed with it.

>>1130632
It depends on what the supplied voltage is. If it's over 4 or 5 volts you should be fine.

>>1130633
Normally those things are powered with 12V transformators. Do i need a higher voltage the more often i split the power line on the different LED series?

Like 12V -> 4 times 3V
and 48V ->16 times 3v?

>>1130632
you can use one resistor value if you split the colors evenly in each string.

>>1130645
you could do up to 2 blues and 2 reds per string.

>>1130645
Not quite. LEDs are nonlinear components. If the voltage across one varies by a little bit, the current will vary by a lot and possibly blow up your LEDs. The way to get around that is to have a current limiting resistor in series. The rule of thumb is something like 20% of your voltage at the least should be across the resistor, so 80% of the voltage should be across the series LEDs.

Don't build it without a current limiting resistor or you'll fry your shit.

>>1130646
So its possible to put LEDs with different Voltage in a string?

>>1130646
>you could do up to 2 blues and 2 reds per string.
Is that meant for the 12V trafo scenario?

>>1130648
yes. you could fit another red or blue in there depending on how big the cap on the other end of the transformer is (12vac -> 17vdc at no load, less with load)

if you use leds rated for a fair bit more current than you're actually putting through them then you don't need to worry so much about forward voltage variation.

>>1130649
what is considered a fair bit more? Mine are meant for 3.2 and a max of 3.5.

So you are recommending 4 LEDs (2x2V and 2x3.2V) per string?

>>1130647
I am aware of the current limiting function of the resistor.
I assume that it reduces the Voltage on the LEDs as well, or else you couldnt power 3V LEDs with a 12V power supply, right?

No i ask myself if i need higher voltage power supplies if i run a greater number of LEDs with it to make sure the 3V are met everywhere? Or is it just the total Ampere, that my power supply can give out, that matter?

>>1130343
build my own temperature control? Nah. I'd rather have something professional grade to diy with.

>>1130652
You can drive any number of LEDs in parallel if your power supply can provide enough current. The higher the voltage, the more you can drive in each series.

It sounds to me like you should really look over some of the basics of electrical circuits. Check out the links in the OP, or Physics for Scientists and Engineers by Serway and Jewett.

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How's my first met at soldering look? I feel good about the closest three pins, and less good about the next three. I made sure to heat the junction and hold the solder on the other side of the pin, but I didn't get the nice solder mound I was expecting on the middle three pins.

>>1130737
Attempt*, not met. Closest as in thumb side (right)

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>>1130737

>>1130331
>>1130665
https://www.amazon.com/gp/product/B01AMC0L2M/ i have this one and honestly the only complaint i can think of is that the iron's cord could be a foot or 2 longer for my usage. other than that its been solid for me. its gone up 5 bucks since i bought it though.

>>1130740
Thanks. I'll fix them tomorrow.

Anyone vaping here? Got a question about ohm's law.

My 18650 battery is rated at 20A. I want to hit 0.15 resistance on my coils but it will exceed the 20A limit and go up to 24.5A.

I know this is dangerous stuff and will wear down the battery. But I wanna know if there is something else I can do to get that flavor aside from lowering resistance? Or is going a bit above the rating relatively safe?

>>1130743

I have that same one (different brand). I tend to agree. Its only real issue is that the cord/air hose aren't long enough. That's easy enough to remedy, though.That being said, mine DOES have an issue that may or may not be endemic to the entire line.

Specifically, the soldering tip (and presumably case) is hot.

As in, electrically hot. I noticed once, using it outside on the concrete in bare feet for some odd repair, that I got a slight buzz when touching the solder and tip to the joint. Haven't opened it up to investigate further but it could be a problem.

https://www.jaycar.com.au/0-to-30vdc-0-to-5a-regulated-power-supply/p/MP3840

Does this look good/shit?

>>1130672
Oh shit, i just realized you referred to current and i read Voltage. It was 3 am here.

So 15 strings with 350 mA would get me 5,25 A,w hich is a bit much for a 12V DC power supply.

Is it corect that i could use series of 8 LEDs if i used a 24V DC power supply?
If the current for each string was 350mA that would get me 2,625 A total.

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Wanting to make a 3-minute timer with mm:ss countdown and a buzzer when the countown ends.

>https://electronicsclub.info/p_timer.htm
Found this but it lacks a display :c

Complete absolute noob here when it comes to practical electronics, despite being 2nd year in electronics college. Only thing I've ever soldered was a 2-LED flip-flop.
Can I learn by doing or is this too much for a first project?

>>1130853
Looks fine for hobby work, but your overpaying and arm and a leg from jaycar, look at a few of the Chinese options, they can be just as good.

Do you have any suggestions for things I should buy to get into this hobby? Is there a beginners kit that you would recommend? I have the beginner books, but not much is going to stick unless I'm actually doing this stuff with my hands, you know?

>>1130623
>What would happen if I tied a 5V supply to the output of a digital logic IC?
As soon as the output is set to low level it's screwed. You can connect the pin via a series resistor to the supply. But idk the purpose.

>>1130933

Yeah I was just hoping to pick it up asap instead of waiting for postage

is it just me or are avrs less featured and more expensive than pics through the entire price range? what am i missing?

>>1130952

Charles platt make electronics second edition

>>1130859
you won't get 3a out of a trashy linear transformer but you can get a cheap 12vdc out switcher that'll provide the current you need.

350ma is a lot for a single string, what leds are you using? you'd be dissipating a lot in your limiting resistor.

>>1131092
Dunno if your observations are correct or not, but price has traditionally been one of PIC's main selling points. They're also made in higher volumes than AVRs, so no surprises there either.

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my ebay ic2 lcd's arrived and one of them was missing the led jumper.

Would I ever need to use those pins externally or am I right to solder them together?

>>1130861
Shouldn't be too bad. I've never used a display but that's the only really hard part. Timing can be done with a crystal, RC, LC, or clock generator, and demultiplexers to divide. Buzzer can use a 555 or any other oscillator. Maybe the same one you use for timing if you pick a good frequency.

>>1131184
a missing jumper on LED? i can't tell if that's to enable the backlight or just the shitty indicator led it's next to.

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>>1130740
Here's today progress. What do you think?

>>1131255
good joints. what's the circuit?

>>1131184
>>1131247
It is for the backlight, the library has backlight control but if you remove the jumper, the backlight will never turn on.

Can safely just solder it together

>>1131317
if you're not running off a battery there's no reason not to

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>>1131317

dont solder the pins themselves so they can be used later. you can solder the connection points on the bottom of the PCB. or use some fine wire to wrap the pins and join them.
as for those jumpers, you can find 'em by the dozen inside old computers.

>>1131342
Wirewrappin like it's 1989

>>1131353
I heard wire wrapping is a stronger connection than solder both electrically and mechanically.

>>1131353
This kind of connection was used in Apollo space program.

>>1131342
You can unsolder wire from pins too tho.

>>1131322

Dumb question but if I was using battery power wouldn't I just use that to power the arduino and get power from there? When would I need to 'externally' power the lcd?

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anything i can do with this husk of an mouse
i have the usb dongle for it
(microsoft wireless mouse 1850)

>>1131414
i missed alot of text for the smaller IC, it reads
NRF A
31512C
1532FF

>>1131414

No, not really. Mice are some of the most highly-integrated pieces of consumer electronics that exist. That optical sensor chip contains everything the mouse needs, in terms of computation. Everything else is just miscellaneous low-value passives, switches, and the mouse wheel encoder. Since you have a wireless mouse, you have one more chip, which is just the radio.

You're probably going to be doing anything with any of this stuff. Even if you knew how, it would almost certainly be a better use of time to just start from scratch.

Honestly, it's better to just leave the mouse as-is and use it for unconventional purposes.

If it's broke, nab the switches and toss the rest.

>>1131420
yeah i figured.
the mousewheel broke but im going to 3d print a new one once i visit my friend. maybe attach a battery management circuit and a small Li-ion battery.

cheers

>>1131357
Mechanical strength (when connecting a wire to a pin) is one of its advantages. Whether it outweights the disadvantages is another matter.
>>1131380
Yeah, that was in the sixties.

Hey fellas, hobbyist beginner here.

I've started reading some of the books in the OP, but I'm a bit of a practical learner and read theories quickly lose its effect on me unless put to some use.

With that in mind, I've looked into buying a breadboard and some few components to play around as progress, but I'm unsure on what other components I can purchase at a local store in order to get started. Appreciated.

>>1131262
Low pass filters and peak detects a microphone signal to control LEDs in time to music. I'll pot the schematic when I get home.

>>1130493
is that one of those ebay units?

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>>1131262
>>1131456
It works reasonably well. I learned a couple things that I'd change if I was redesigning it from scratch:
1. Cutoff frequency should be much higher - probably just below vocal threshold. I wanted to have it be in time to rhythm, but I didn't realize that rhythm would often cover most of the audio spectrum, such as drum hits, which are a short, almost white sound.
2. Use bigger resistors on the LPF and smaller caps.
3. R12 is a workaround. C5 was charging and would stop the circuit from working for some reason, but would slowly discharge and start working again when I probed it with my scope. Not sure what the cause is, or what a better fix would be.
4. Using an audio jack input would have been easier than the mic, since it's going to be sitting next to the DJ the whole time.

How likely is it that I busted a linear regulator by overheating it while soldering? It's a 10V nominal output, 12V input, and it's outputting a stable 11.11V with the necessary caps in place.

Is that what you'd expect a blown out linear regulator to do?

I've got a couple of these and want to replace the LEDs with something brighter. Is there a good way to pop these housings open then reseal them without damaging anything?

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>>1131856
>forgot pic

>>1131857
It's probably either got plastic catches that'll snap or an adhesive. Either way, you'll have to glue it back together.

>>1131864
Do you think heat would help them come apart? I had another LED in a plastic housing that I found was glued together, and it cracked when I pulled it apart instead of separating the glue.

Is there a way to speed up or slow down the tempo of an audio signal without changing the pitch that DOES NOT involve using DSP?

I can't code my way out of a paper bag, let alone write complex digital audio processing algorithms for an MCU/FPGA. I need to know if there are any analog methods that will work.

Basically looking to add various effects options to an equalizer I'm designing. I'd like various things like speed up/slow down tempo, reverb, distortion effects, etc.

>>1131910
Change the tempo? So play it at 0.5x or 2x speed with the same notes? You can't do that live (for obvious reasons), so you'd need some sort of memory to store the audio input temporarily, or have the audio stored in a memory card in the first place. That's all very digital. If you want something completely analogue, I guess you could play a record on a turntable with speed control, but the pitch will change. Pretty sure it's digital or nothing.

>>1131910
>Is there a way to speed up or slow down the tempo of an audio signal without changing the pitch that DOES NOT involve using DSP?

Sure, if you can figure out a way to implement an analogue Fourier transform, store the audio to be processed, analyze it and apply the transform, then play the result.

Which is going to be way harder than just figuring out how to do it with a microcontroller. It's certainly doable, it's just...why would you go through all the trouble?

And, as has been pointed out, I'm not sure why you'd want that on any sort of equipment for live performance. Obviously, you can't process llive audio faster than real time, and I can't imagine why you'd want to play it back slower.

I want to do some little RasPi projects, but having trouble finding displays that fit what I'm looking for. Do they need to be specifically for RasPi, or can I just take any display and make it work? Mostly just don't know where to go next on that search train, any key words to look for?

>>1131865
Get an extra one and smash it open to see how it works.

>>1131443
>but I'm unsure on what other components I can purchase at a local store in order to get started

Don't even bother. Unless you have a local supplier that SPECIFICALLY deals in discreet components, you're going to be paying truly absurd markups for your parts. A an example, Radio Shack was, fairly recently, selling generic red/green LEDs in 2-packs for $1.00. You can get the same ones for less than $0.01 each off eBay or similar.

I default to eBay for non-critical parts, and DigiKey for stuff I need to be legit.

>>1131787

I'd expect it to not work at all, really. Is this an adjustable regulator? Might be crap/out of spec resistors making an odd ratio for the feedback network.

So I noticed you posted a list of books. Where would I acquire these?

>>1131974

torrents, dummy. everything that exists in digital form can be downloaded from torrents.

>>1131975
But I don't have virus protection...

How much would it cost to run 150W 24/7 each year in the UK? or how do I work it out, only information I have is it draws 150W maximum

>>1131980

look at your electricity bill. it should say something along the lines of 6 cents per kWh, or whatever. then use grade-school math to figure out the rest.

I have a 4 pin fan here, with a fan controller that only has 2 pin, can i connect the 4 pin fan to the 2 pin connector with just the gnd and +12vdc? The controller is 5V as it connects by usb.

>>1132082
yeah probably, the other two is going to be tachometer and maybe pwm

>>1132088
From what i can find on google, the green one is sense, what is that? The other is control but this one i know for sure that it can be out, it's what happens when we put a 4 pin on a 3 pin connector.

Hi, /ohm/.
After following the directions in the attached link, I stumbled upon the sending the data from the rpi to the launchpad. I'm not sure, or better said, I don't know if I require another piece of software on the rpi end, llike putty for raspbian.
Your help would be appreciated.

>>1132264
forgot link
http://mitchtech.net/raspberry-pi-msp430-spi/

I'm a retard and barely know what I'm talking about, but please humor me.
Who the fuck decided to make a light emitting diode? Like why a diode? Why not any other basic electrical component? Is it's ability to be a diode just a byproduct of the way it gives off light or something? Or did someone actually think tacking a light on a diode was just a neat idea?

>>1132274
If you'd bothered to Google "light emitting diode" you would have found it was a discovery not a decision.

Try it yourself, Wikipedia explains the history quite well.

>>1132274
incandescent lightbulbs are light emitting resistors

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Hey /ohm/, I'm a bit limited on test equipment right now (not even a multimeter at present!) so i have a back to basics question.

I just want to make a simple LC tank circuit, but I can't make it work!

Ive tried connecting everything in parallel, but I don't think I've actually made it resonate. I should be able to see the voltage sloshing back and forth using two LEDs in parallel with the LC tank... Right?

I have the components in pic related. The caps pictured are 470 uF. I don't actually know what value the inductors are lol. I also have an assortment of resistors and lots of alligator clips, and other basic odds and ends.

>>1132324
A bell or organ pipe doesn't vibrate by itself, does it? Neither does a tank, it still needs to be driven. Or at least "whacked" but your Q is going to determine how quickly it dies out. And unless you build a 30 Hz or lower tank good luck seeing it in action.

A little late to the blog here, but I just wanted to vent about autodesk. Fuck them for buying eagle and turning into a monthly subscription model product. They also revoked the educational license I am using and stuck me with the free model and an option to get it back with an awful max board size.

What an awful company that cares only about profits and corporate software bundles and not about people actually doing things with their software. Now I have to teach myself KiCad and transfer over all my projects and libraries. Fun.
/blog

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>>1132342
Pic is what I'd like to accomplish. The action of connecting/ disconnecting the battery with a switch or button should start oscillation, no?

Right now I'm thinking my inductors may not be inductive enough :p

>>1132472
Yeah, but the oscillation will last a fraction of a second.

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So I'm trying to get a harddrive motor to spin (3 phase brushless dc motor). I've already distinguished the neutral terminal from the 3 other phase terminals.

Pic related is my circuit to control the motor. I'm using a microcontroller to generate the pwm signal. I wired everything up on a breadboard and put power to it. Motor doesn't move and my external power supply (that is supplying the 10VDC) is showing very high current and low voltage output.

Any ideas what I may be doing wrong here?

>>1132491
Your mosfets require 0V/10V drive signal. If you feed them with logic level signal, your P fets will conduct always. Alternatively, you could lower the mosfet supply voltage so that it's equal to your logic supply.

I just watched a video of Alex Jones saying the Internet of things was a globalist plot

I can kind of see that... Infact he's probably right

>>1132491
There is no neutral on brushless motors. If its got a 4th wire, its probably for the hall effect sensor. The motor doesnt spin because your pwm could be at a wrong frequency, or the windings are shorted.

>>1132648
Or youre using the 4th wire to spin the motor lol

>>1132472
>The action of connecting/ disconnecting the battery with a switch or button should start oscillation
This is how perpetual motion machines work.

>>1132472
Use an OPAMP (a transistor would also probably work) to continually drive the circuit, and if you can't see the oscillations of the LC circuit, amplify it to a speaker and hear them!

>>1132560
My mistake, I only used N-FETs when I breadboarded. That could have been the problem. Though, I don't know what you mean that my P-FETs would always be conducting. I'm basing this off an H-Bridge in the sense that when I drive my gate voltage high, the P-FET starts pumping out the 10V and the N-FET turns off, and visa versa.

I don't know what purpose would lowering the mosfet supply voltage would serve. I'm trying to use the mosfet arrangement to amplify the PWM signal so that the motor will get enough juice. Otherwise I'd just hook up the pwm signals straight to the motor terminals and call it a day.

>>1132648
>>1132651
I did a resistance check for each terminal. The 4th wire had a resistance of 0.3 ohms when tested with every other terminal, whereas the other 3 terminals tested with eachother showed a resistance of ~0.6 ohms. To me, that looks like the behavior of a neutral winding. Is there someway to confirm the 4th terminal is a hall effect sensor?

I did set the PWM to an arbitrary frequency. How would I find out what frequency I should be tuning my pwn at if this is the problem?

>>1132662
Yeah I tried swapping the N-FETs back to the P-FETs like I drew in my schematic. Still the same results. I do feel like something is shorting out due to the high current draw from the 10V power supply.

>>1132662
>To me, that looks like the behavior of a neutral winding
There is no neutral winding in a brushless dc motor, wtf. The speed controller uses all three phase windings one by one to send pulses of current to, there is a permanent magnet to take care of the rest. For motors where precise rpms matter, will have a hall effect sensor. Youre probably being confused by 3 phase ac induction motors where the stator has windings as well, but those are nothing like a modern hdd brushless dc motor. All windings should have same resistance reading. Use the ones with .6 ohms and motor will work. Do not connect the 4th wire to anything.

>>1132678
That's what I HAVE been doing... I've been using the 3 terminals that are rated at 0.6 to connect to node A B and C of the mosfet controller and leaving the 4th terminal of the motor disconnected. Still doesn't quite solve my problem; I don't know how I'm "shorting" out the 10V power supply.

Should I be looking to use the 4th terminal as feedback somehow to tune my 3 phase pwm signals? If I just arbitrarily ramp up my pwm frequency, would that be enough to get it running?

>>1132679
you can cold start bldcs by doing that but they won't run great. typically you have 3 hall sensors to provide feedback or you just alternate measuring the emf on the idle winding. maybe hdd motors just have a single hall or a full fledged tachometer in them.

do the frequency ramp idea and watch the fourth winding on your scope.

>>1132703
>>1132679
lol it turns out they're cheap fucks that couldn't afford 3 resistors. the 4th winding is a center tap to provide a reference for emf sensing. you can ignore it unless you want to break out some comparators and make a real drive circuit.

>>1132703
>>1132705
Yeah that's what I was trying to explain what I determined the 4th terminal as a "neutral". I guess I started to doubt myself.

As for backemf, I was intending to use it in a feedback loop to better control the motor, but I'm leaving that on the back burner as I'm just trying to get the motor to spin right now.

>watch the fourth winding on your scope.

If I had a scope I would. Probably what is making this whole thing more difficult.

>>1132709
get a scope senpai, you might have undiagnosed driver issues.

>>1132712
A good one is so expensive though (granted, I haven't really done too much research into it) and I don't have much money to throw around.

>>1132715
just go pull a $2k dso out of the nearest dumpster. that's what everyone does.

>>1132717
Yeah I did that (got one from a university physics lab garage sale) and the thing just gives me erratic readings.

So like, either I fix the thing or I go get another one from somewhere else.

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>USB battery pack auto turn off
I have a usb battery pack that only has a momentary switch, you press it and it turns on, looks for a load then if there isn't one it turns off.

This means I can't power low power things like book lights or 360 controllers.

If I made an inline usb cable that bridged the + and - leads with a resistor would that make it think there's a larger load and stay on?

Parallel to draw more amps and not change the voltage, right?

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i had an autistic fit after reading some anon's 555 timer post and i made a 100 hour timer out of dip16 4000 series logic.

it's missing debouncing caps and the xo isn't shown because no simulato. i still want to add a timer for a buzzer. needs some work to optimize the gate ics.

I am designing an audio filter and rather than have two separate filters for the L and R channels I want to do basically feed the signals into an analog multiplexer (like the CD4016) and alternate between them at a frequency much higher than audio frequencies (100+kHz) then demux them afterwords to send to the L and R outputs.

My main concerns are switching noise and harmonic distortion. I can low pass filter with a cutoff a little over 20kHz to take care of the switching noise but distortion is a major issue. If the clock frequency is exactly 100kHz the harmonics in the audio frequency range are generally below -50dBv however even the slightest drift from that frequency will increase the amplitude of the harmonics dramatically.

I doesn't actually sound that bad, it makes the sound sound a slight bit "sharper" square-wavy-er but it is noticeable.

Basically as it stands now I would need a very stable oscillator at least 0.01% or better to make this viable and minimize distortion.

Wondering if there is a better way or if I'm overlooking something stupid.

>>1132721

yes, obviously.

>>1132846
0.01% is easy, just divide down a crystal osc. Your weird interleaving thing is nuts though.

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>>1132860
The goal was simply to minimize the number of components. This is a state variable filter for just ONE audio channel. I would need to duplicate nearly all of it for stereo and I don't really have enough breadboard real estate for that.

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>>1132717
I might as well ask;

I have never gone dumpster diving let alone dumpster diving for electronic test equipment... How the hell are you fuckers getting $2000 scopes out of dumpsters?????? Where the fuck am I even supposed to start looking? (I live in hongcouver btw if that will help).

>>1132869
what a fucking pig sty

>>1132869
Learn to manage your circuit better senpai. Use smaller wires at least

>>1131978
Just use your common sense or libgen.

>>1132873

it's a meme dude. you'd have to spend 18 years diving to come up with a find like that. or you could find one first time out. thats the way randomness works. it's why (dumb) people buy lottery tickets with a 1 in 13M chance of winning.

>>1132906
Well shit I thought there was some electronics gold mine that I just didn't know about. Guess I'll just have to continue saving up for a decent scope.

As a side note, are there any reliable guides out there to buying a scope?

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hey everybody!

a few weeks ago, you may recall me as the anon who was building a switchbox for music purposes. position A of the switch would go to a momentary "on" (n.o.) button while position B would go to a mute (n.c.). The problem I was having was, initially, with the schematic; the real problem was I could still hear a signal from the output when the hot and/or gnd leads were physically separated from the input i.e. mute.

Long story short, after a lot of trial and error, I think it was all a matter of having too much gain on my mixer. What concerns me is I normally use my mixer at or near full blast for shows, so ideally I want something that completely kills the signal on command. I did find that this switchbox actually had less signal passing through than a bare cable, however, so it's not as big of a deal.

I also found something unexpected: when the switch is in momentary on mode, where the n.o. button should be the only button working, the mute button will still make a sound if pressed. I included a pic of my prototype; I can also draw up a schematic if it's too messy.

note: from that trial and error mentioned earlier, I found that disconnecting both hot and gnd leads for a mute function actually works worse than just disconnecting the hot alone. I also long came to the conclusion that the standard killswitch schematic that shorts the outpit with an n.o. switch simplt doesn't work.

>>1132973

>no shielding
>wonders why it leaks

Hi guys, I'm planning on being a distributor for electronics based in the US. Are there any specific modules you would like to acquire quite a few of at a time? I am currently negotiating the price on 1000 esp12's, and have many other orders in for some discrete ICs. I will beat any listed price on Ebay/amazon, provided you pay for shipping costs. Let me know what you think.

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I need some help.
I have two plugs plugged into the outlet. One is for a radio and uses 250v and 15A.
The second is a kindle charger which uses 100-240V and 0.3A.
When I switch on the radio first then plug in the kindle after - the kindle switches off as if there is some sort of electric pulse that switches off the kindle.
Help.

>>1133052
kindle charging is, IME, pretty fucking random at the best of times, prob nothing to do with your socket. An 'offishul' AMZ charger seems to be your best bet, your mileage may vary with other chargers, altho, it shouldnt

I once had a (fairly expensive) multi-output hi-power USBcharger thing, could also use for laptops etc. - that remains the only one I never had a hassle with, besides one Samsung phone, that cherged everything and quick. Lost the fucker by house moving, or, some1 stole it, the bastarts. But OT, try plugging in the kindle (or radio) to a different socket, use extension if needed - doubt that make a jot of difference tho.

>>1133052
>One is for a radio and uses 250v and 15A.
Are you trying to contact fucking Jupiter? Jesus. My table saw draws less power than that.

>>1133052
3kW radio seems normal.

>>1132920
What do you plan to use the scope for?

>>1132869
Well commutation is going to do some kind of weird oversampling thing, it's going to muck up your signal for sure.

>>1132973
>>1133044
Yeah legit try wrapping everything in electrical tape, wrapping it all in tin foil, then tying that to ground. Detaching the ground makes odd things happen. You should bypass the two buttons by going out and buying a DPDT toggle switch and a SPDT momentary button. And buttons can be pretty noisy, I'm not sure what capacitive effects you're getting through them, you might want to put a preamplifier before the mute button setup so that the amp amplifies much less of the noise, that will probably solve your problems.

>>1133081
Low power mostly. Probably to troubleshoot analog and digital circuits for the most part. Granted I would love if it had high power capabilities as I do want to build my own electric motor from scratch some day, though I assume more features means more pennies.

>>1133137
Most scope inputs can handle up to 400Vpk. That will probably suffice for your motor. Just make sure you use flyback diodes to prevent inductive spikes if you're doing any kind of switching with an inductive load like a motor.

>>1133141
Well that's good to know, any particular models/brands you could point me to that won't break the bank? I saw some portable scopes at my local electronics hobby shop for like ~$200, but I assume they're trash.

>>1133149
Shop around for vintage oscilloscopes on ebay. There's a lot of analog scopes for under $100 and early digital scopes for under $200.

Shoot for no less than 20MHz bandwidth but 50 and 100MHz scopes are usually affordable. Higher the bandwidth the better unless you are absolutely positive you are never going to measure any frequencies higher than a few megahertz. For digital scopes shoot for samples rates of at least 100-200MSa/s.

I have three oscilloscopes. A Tektronix 2225 50MHz analog scope ($50 +~$25 shipping), a Tektronix 2430A 150MHz 100MSa/s digital oscilloscope (~$120 and free shipping I think?), and an HP54645D mixed signal oscilloscope 100MHz 200MSa/s which includes a 16 channel logic analyzer (had to buy the probe separate) and the Measurement and Storage module (HP54659B) which allows you to perform derivatives, integrals, and FFT on signals (~$200 with free or at least relatively cheap shipping).

These are all fairly decent models and should serve as a good baseline to help your purchasing. Make sure anything you buy has at least been power on tested. Even better if the seller can display a signal or if they calibrated it but that's not always the case. Don't buy anything that's listed for parts or not working unless you feel like trying to repair it. Good brands are Tektronix and HP/Agilent/Keysight (same company) but other brands like Hitachi, Hantek, and BK Precision are fine too.

If you want a more modern scope save like $400-500 and get something like a Rigol DS1052E. Modern scopes usually have bandwidths around 500MHz to 2GHz and sample rates of over 1GSa/s. But honestly for your first just get a vintage scope. They are typically good quality and were high end for their time. Plus the CRT displays have a nice vintage feel. They might need some clean-up but other than that they are great.

>>1133099

I don't understand what you mean by getting a DPDT and one SPDT. The idea of this project is to switch between the two buttons: a momentary on mode and a momentary off mode. So there'll have to be one switch and two buttons regardless of how many terminals they have. Could you please elaborate?

Shielding seems like the hot ticket, will post results when I can

>>1133189
>>1133099

Or is your idea to have one button whose functionality is determined by the switch i.e. the momentary on and off buttons become one button and the switch position dictates whether it is momentary on or off? Provide a schem please.

>>1133196
See >>1125786

>>1133199
OK, now I get it. Wow. I gotta say, I only understood it when I re-drew it, but that's still pretty clever. Have enough at home (maybe) to try this, results later...

new thread

>>1133263
>>1133263
>>1133263

I want to be able to plug a device that I want to make into an outlet, and I am trying to step down the voltage by making a transformer, however my wire is 18 AWG, is there any danger here?

File: 63-00.jpg (345KB, 1200x900px) Image search: [Google]

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>>1133270
Instead of potentially killing yourself why not just buy one of those switched mode power supply adapters. Get one suitable for the voltage and current your device requires and just throw a DC jack on your project and you're done.

It's less risky for you and will probably work better than a self-wound transformer anyway. Just don't Jew and get a cheap one from China cause the quality on some of those chargers is awful.

>>1133292
Because the potential to kill myself makes it exciting :)

>>1133293
Alright, if you like living on the edge then.

Piece of advice if you're going with the transformer design, you are going to need a lot of windings for the primary and a large high permeability core.

If you just take any old transformer core, slap 10 windings on the primary, and 1 on the secondary it will work... but only at some ridiculous frequency like 100MHz or thereabouts. It will not work at all for 50/60Hz mains power. Transformer design is very complex and there are a lot of traps.

Fun to experiment with though if you have a few cores, some magnet wire, and a sweep generator lying around though.

File: H313 oscilloscope.jpg (584KB, 3072x2304px) Image search: [Google]

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>>1129429
If you live in Europe/Eastern Europe (or even better, Russia) you can find old Soviet fully functional oscilloscopes for less than 60$

>>1133603
What is this, a scope for ants?

The trace itself takes up over two whole lesser divisions, how can anybody reliably read that scale?

>>1133746
Hey, it costs around 50$, what did you expect

>>1128736
wait, theres a radioshack in nova?