/ohm/ electronics general

Was just recommended and then asked to interview for a job that requires 1 year soldering experience and experience with simple electronics. I have minimal experience with the subject, yet the job perks have inclined me to interview anyway.

Tl;dr how do i act like i know what im talking about when it comes to soldering?

Just go on YouTube and watch a shit ton of soldering vids. Then learn a ton of words like transistor and resistor and capaciter and shit

>>922134
Just go on YouTube and watch a shit ton of soldering vids. Then learn a ton of words like transistor and resistor and capaciter and shit

>>922134

Real jobs actually care about soldering? it seems like a retarded easy skill to me.

>>922140
Surface mount components are so small now that a lot of soldering has to be done under a microscope and it's physically impossible for people with shaky hands or poor coordination. There are still jobs doing this by hand because it isn't cost effective to set up a pick and place machine when only two or three prototypes need to be assembled.

>>922154

But that is particularly specialist.

>>922157
I don't think this is that specialized of a job, entry level for a local company. Dealing with high power LEDs. Probably not that level of detail.

stupid question about LEDs for auto.

if you have a regular bulb at 100 lumens and it shines thru a screen to make it green, like in the speedometer, the only light wavelength making thru the other side is green, but is there a way to hazard a guess how many lumens is making thru?

>>922179
A common emission spectrum for a white led looks something like pic related. Green light is around 500nm - 570nm so I would think taking the area percentage under this region should give you an answer. Not too sure on Physics though so someone correct me if I'm wrong.

File: images.jpg (17KB, 470x313px) Image search: [Google]

17KB, 470x313px

>>922189
Forgot pic

>>922134
Fuck, what job?

>>922212
I shit you not, the job title is Lightsaber Technician.

>>922261
Prop master/assistant? Make sure they use Robertson or Torx instead of shitty phillips next time.

>>922276
Actually for a company called ultrasabers that makes stuff for LARPers. Probably just assembling the LEDs and soundboards inside of stuff.

>>922117
Where to get resistive wiring? For building a small heater for a truck.

>>922314

toaster

>>922314
Iron

>>922314
A hundred vape rigs running in parallel.

File: help.png (16KB, 847x381px) Image search: [Google]

16KB, 847x381px

I feel so dumb. I had all the classes and all...
I'm using the LM386 amplifyer and have trouble understanding what that 0.05µF cap and 10 Ohm res does.

I'm no genius but I know it's meant to be a low-pass filter.
But the math seems to tell me it's useless ? Since potential U_2 ends up the same anyway i mean. I've tried to calculate the transfer function (U_speaker/U_in) of that part using resistor R_2 as speaker (which is bad i reckon now), and found something independent of the filter. I'm so confused.

I don't even need a detailed explanation, just tell me what I forgot...

>>922339
It's called a Zobel network and it's there to counter speaker's inductance - usually to prevent oscillation but sometimes to prevent the inductive kick from fucking with the transistors too.

>>922363
Thanks a lot, just what I needed !

Has anyone in /ohm/ found a job using their electronics repair skills yet?

>>922393
tube amp tech reporting

File: bls_dont_lie.png (14KB, 526x205px) Image search: [Google]

14KB, 526x205px

>>922393
Anyone who says they have is lying

Just go be an electrician if you like circuits and instrumentation

File: 1451502020181-289216254.jpg (1004KB, 2048x1152px) Image search: [Google]

1004KB, 2048x1152px

>>922399
tell me more about how i dont do what i do, friend

File: pwm_log.gif (30KB, 440x200px) Image search: [Google]

30KB, 440x200px

AVRfreaks.net does not fuck around

File: 450-00.jpg (96KB, 1200x900px) Image search: [Google]

96KB, 1200x900px

I'm looking to build a In-14 nixie clock from scratch and I don't know how I'm going to signal 10 different cathodes without using something ridiculous like 10 relays, switching via shift register. I don't believe transistors handle 160V very well so this cheaper alternative is out of the question.

>>922463
>I don't believe transistors handle 160V very well
It's not hard to find a transistor that can handle that.

>>922314
Frost free refrigerator

>>922469
Ok, I figured they were typically used for lower voltages but if they're optimal for this voltage as well, I'll grab some online. I wasn't as much concerned about if they could handle it, rather, if I should use them. Thanks anon.

>>922134

Hold a soldering iron like this until the capacitor explodes. The interviewer will be impressed with your skills and hire you on the spot.

File: third degree burns.jpg (207KB, 953x1300px) Image search: [Google]

207KB, 953x1300px

>>922472
Forgot the pic


>>922471
Pig backing on this, how do you get a transistor to conduct the full 160V using a 5V signal? Wouldn't it let only a little bit more than 4.5v pass if the voltage is applied directly to the base?

>>922476
(I posted the original question) You raise an interesting question. However, I'm pretty sure if you send a small current to the base of an NPN transistor, the larger voltage (from the collector) will be utilized.

TLDR: If a transistor only passed along the voltage of the base signal, it would be a strangely designed diode.

>>922463
Duplex, cuts down the shift register count to half

>>922189
Generate some function that models the bandpass filter effect of the lighting gel and multiply it with the white LED spectrum curve?

Guys do any of you know where I can find a schematic for the first xbox?

I went to fire up the old girl yesterday and it's dead. I'm between semesters right now so I'm thinking this is a good project.

Could I put in a 220v outlet myself, assuming that I have zero experience? How much would it cost for me to hire an electrician to put the outlet in?

What are the advantages of using a MOS differential amp vs a BJT differential amplifier?

Any reason to choose BJT over MOSFETs?

>>922573

How much current is going into the gate of a MOSFET vs into base of a BJT?

What is the bandwidth of a MOSFET vs a BJT?

That being said, a MOSFET differential pair has a finite input differential voltage.

What's my best option for getting small circular 2-3in diameter PCBs printed and preferably assembled?

>>922567
More info, I'm going to be powering a welder from this outlet. Do I need to have the welder first so I know the amp draw fromt he welder in order to wire the outlet correctly ?

What's the cheapest place to order blank circuit boards from in the US?

>>922617

maybe not in the US, but http://dirtypcbs.com/

>>922651
Good shit thanks

>>922567
>>922600
If you aren't an electrician then don't do mains work, other people may live in your house in the future, needs to be certified.

Is it a regular plug on the welder or one of the special high current ones?

>>922667

ehhh don't buy the electrician meme. sounds like union BSing to me.

Don't be afraid to atleast research what you would need to do for the job.

>>922668
When it comes to house wiring this is a good rule of thumb (and legal mandate in most areas):
Anything that requires you to remove the back plate from a fuze/breaker box panel to get at the wires behind it needs to be done by an electrician. You can add your own outlets and light switches by connecting them to existing circuits, but adding a new circuits needs a professional.

If the house burns down in 20 years because the new owner put gasoline soaked rags in the clothes dryer you'll find yourself in court and having to pay for everything.

>>922679
>>922667
Do you really have to certify every fucking piece of electrical work in burgerland? That's fucking insane.

All that would do is generate more money for electrical unions and lawyers with bullshit lawsuits, it won't stop random rednecks adding their own half-assed, house burning down circuits.

>>922567
It's fucking easy man. Find the closest point, run a wire from it to your new location. Strip and connect wire to first and second outlets in the same way as the original. If you are unsure just google it.

As for power loading, find out which circuit you want to take it off and see what else is running on it. If you have fridges/ovens and shit then use a bedroom circuit.

I've been looking at the practical differences between FETs and IGBTs. I've read that IGBTs have much better power dissipation characteristics than FETs because dissipation has a mostly linear relationship with current instead of an exponential relationship. The formulas are Pd=Vce*I and Pd=Rds*I^2 respectively. In practice though it seems like Vce is typically two or three orders of magnitude larger than Rds so that dissipation is still worse with IGBTs than FETs up to high currents like 100A. With that in mind, what exactly is the benefit to IGBTs?

Am I misunderstanding something? I come from a mechanical background so I don't know (or care honestly) about the theory, just what the datasheets and textbooks say.

>>922694
You're basically right, but it is particularly true at high voltages. That is, the higher the device voltage rating is, the lower the Id/Ic needs to be for an IGBT to win. Well, assuming equal chip size, which roughly translates to equal price. Partly due to this, the most MOSFETs are relatively low voltage devices and the IGBTs high voltage devices.

>>922599
Dunno about "best", but Seeed Studios have an assembly service. If it's hand-solderable and you don't need mass-production quantities, try asking around at local hackerspaces or colleges for some hungry/thirsty EE student who'll assemble them.

>>922599
Also, if it's SMT, you could convert a convection oven into a reflow oven for DIY assembly. Even the cheap PCB fabs give the option for ordering stencils nowadays.

Are insulated terminals going to prevent a positive/negative signal from grounding each other when in close proximity? I ask because I discovered my blower motor doesn't have a wire harness and now I have to make one myself.

Fuses are good, motor works, resistor is fine, and there's power in the wires.

File: þráðlausa.png (541KB, 708x390px) Image search: [Google]

541KB, 708x390px

Hey, /ohm/
I read an instructable about converting a laptop bluetooth receiver (?) into USB and pic related is the one I got.

Model number is T60H928 and google says it is an USB 2.0 device just inside a laptop.

Can anyone help me identify the pinout of this thing and preferably in what order (I am extremely colorblind)

Thanks in advance.

What is the easiest to set up SPICE (or equivalent) circuit simulator? I've tried so many different programs but I've always hit a wall somewhere and given up before I can get simulation to run properly. I'm pretty computer-dumb. I've been using this: http://www.falstad.com/circuit/circuitjs.html for small projects but it is clearly severely limited for anything of modest complexity.

File: 8614-int-switch-n-fet.png (1KB, 366x344px) Image search: [Google]

1KB, 366x344px

>>922476
>Wouldn't it let only a little bit more than 4.5v pass if the voltage is applied directly to the base?
If you wire it as a high-side switch, yes. (>>922484 is wrong)

What you can do, however, is tie the positive end of the load to +160V, negative end to the collector and the emittor to GND. Then, whenever you bias the transistor by applying voltage to the base, the negative end of the loads gets pulled almost to GND and current can flow through.
https://learn.sparkfun.com/tutorials/transistors#operation-modes

Note that a MOSFET would be much better for this application because of lower on-resistance (less wasted power, easier cooling). See the attached pic.

>>922599
Check out https://beta.macrofab.net/
Probably not the cheapest, but looks like they put in a lot of effort

>>922694
>The formulas are Pd=Vce*I and Pd=Rds*I^2 respectively.

Wait what. Doesn't Vce=Rds*I?

What is the true value for the constant approximated to 1.1 for the 555 monostable pulse length calculation?

>>922564
What makes you think Microsoft would release such a document?

That said, my xbox died recently as well. I managed to revive it by replacing a few busted/bulged caps with these: http://sg.element14.com/panasonic-electronic-components/eca0jhg332/cap-alu-elec-3300uf-6-3v-rad/dp/1848528

Open your xbox and disassemble it, there should be a bunch of caps roughly that size, see if they look bad.

Here's a video showing how to do the repair: https://www.youtube.com/watch?v=4to3cOPkfFI

Any caps of the same voltage and capacitance should do, as long as they physically fit.

I'm suggesting this because it seems to be a fairly common fix, and it has my endorsement.

>>922134
Get 1 year soldering experience.

For a ~4.5v supply, is a 100 ohm resistor high enough for an LED?

>>922339
>lm386
If you haven't already make sure you put a good decoupling capacitor right across the power pins of the chip, this one likes to oscillate.

A 100nF ceramic + 100uF electrolytic is bullet proof.

>>923085
In most cases yes for a standard 20mA LED. What is the forward voltage of your specific LED?

File: igbt.png (37KB, 435x375px) Image search: [Google]

37KB, 435x375px

>>923006
Not on IGBTs.

>>923006
IGBT's have a standard junction drop across them.

This is what makes IGBT's so undesirable for low voltage switching compared to MOSFET's.

Hey /ohm/, is it acceptable to use 2 Li-Po cells in parallel when they're 0.05v apart? What's the safe margin for such a thing?

>>922810

Use a multimeter while this is connected to find the power pins, then guess the data pins, nothing bad should happen if you mess those up, just don't fuck up the power pins.

What would be the consequence of connecting a 10 A brushed universal motor in series with a 60 watt incandescent light bulb?

I want to use the light bulb as an experimental method of limiting inrush current to the motor windings. The last time I connected this motor straight to the mains, one of the TRIAC leads exploded violently. I don't know if that's because I did a bad soldering job or because I removed the motor's power control circuitry.

>>922393

Technician in university's solid state electronics research lab. Got employed to maintain workshops and work on my final year project. Most of my skills are from repairing shit I gather and occasional DIYing.

>>923295
The light bulb would work as a fixed resistor, so it would probably work, but the correct method involves using a NTC thermistor

File: WP_20160101_13_28_25_Pro.jpg (1MB, 3072x1728px) Image search: [Google]

1MB, 3072x1728px

I've been told I need a shit load of batteries to do DIY electricity generation stuff. Is this a shit load?

Also I have a bunch of emergency lights that don't work. How do I fix them? They were not working before I took the batteries out. I testes the batteries with one of those continuity tester things and they do have continuity, so I think it's something else that's wrong with them. Are there common problems to look for?

>>923326
If a battery has <100R resistance between + and - then it's definitely fucked.

>>922810
The twisted pair is undoubtedly data. D+ and D-, on the other hand, your guess is as good as mine. The other two would then be power, with the darker one being ground. Good luck.

File: WP_20160101_13_48_54_Pro.jpg (1MB, 3072x1728px) Image search: [Google]

1MB, 3072x1728px

>>923328
Which thingy do I set it to to test that

>>923293
Probably, but I personally don't fuck with LiPo

>>922393
no
but i went to college for EE and got a job that way

File: 1451674195771.jpg (2MB, 3072x1728px) Image search: [Google]

2MB, 3072x1728px

>>923332
This is the resistance measuring section of your meter. You should start in the largest range (2M) and then if you don't get a reading, move down to the next largest one. That being said, you shouldn't connect the meter across a voltage in resistance mode so you should probably figure out another way to measure the internal resistance.

>>923380
Do I need a different meter? I think I've got other meters.

>>923383
I'm not that familiar with batteries so I don't know if the <100ohm rule the other anon was talking about is right but if that is right here's what I would do. First use the meter in voltage mode to verify that the battery outputs the right voltage. i.e. if its a 24V battery, set the meter to the 200 range in DC volts mode (the V with the dashed line under the solid line, not the V with the sine wave) and expect to see 24 give or take a volt.

File: voltage-divider.gif (1KB, 200x300px) Image search: [Google]

1KB, 200x300px

>>923386
Whatever voltage you just measured, remember it It will be Vin. Then to measure the internal resistance, hook up a known value resistor across the battery terminals say a 10kohm and then measure it like a voltage divider pic related. If you think of the internal resistance of the battery as R1, then you can measure Vout across the terminals of the battery, and calculate what R1 must be based on the formula and the known values of R2 and Vin.

>>923387
oh and don't use a small R2 otherwise you'll short the batteries.

File: WP_20160101_16_02_30_Pro.jpg (1MB, 3072x1728px) Image search: [Google]

1MB, 3072x1728px

>>923386

>>923388
and incase you suck at algebra, R1=[(R2*Vin)/Vout]-R2

>>923389
6.2 is fine for a 6V rated battery.

>>923391
since its only a 6V I'd use a 1kohm resistor. If the voltage with the resistor connected is any less than 5.7 you have an internal R higher than 100.

>>923391
Yeah, I figured they all worked. I guess my first post might have been misworded. When I said I figured there must be something else wrong with them I meant the emergency lights, not the batteries.

I would like to know if anyone has experience fixing emergency lights, and what some common problems I could look for are. And if this is enough batteries to do something neat with. Like a /diy/ water turbine or some shit.

>>923393
I guess I could take the one battery that I know works around and test all of them with the working battery, because some of them are sitting at like 4.7, but I think that might be because they are rechargeable and they just weren't charged all the way when I took them out. An easier method would be nice though, because there's 7 not working emergency lights, and they are pretty high up on the walls.

>>923395
Idk exactly what you mean by emergency lights, but if its just some battery powered lights without any other circuitry you could use that continuity tester you mentioned earlier. Put the lights in whatever position they would normally be turned on in if they're on a timer or something. With the batteries out and the lights in, there should be continuity between whatever two leads you hook the battery to. If there isn't then either the bulb is burnt out or there's a break in the wiring somewhere. With the batteries out and the bulbs removed there should be no continuity otherwise there is a short in the wiring somewhere.

>>923393
This would be to test the batteries based on otheranons reccomendation and
>>923399
this would be to test the lighting circuit.

File: WP_20160101_12_51_43_Pro.jpg (1MB, 3072x1728px) Image search: [Google]

1MB, 3072x1728px

>>923399

File: WP_20160101_12_09_06_Pro.jpg (1MB, 3072x1728px) Image search: [Google]

1MB, 3072x1728px

>>923411
Sorry for the bad picture, I took it just to show the burnt looking part. I could climb back up there and get another one maybe. But there's seven like this and I might end up buying seven new ones if I can't figure this stuff out and I really don't know anything about them.

>>923417
That's the insides by the test button, I'm not sure if that helps at all.

>>923418
They are hard wired in with a battery back up. When I hit the test button they don't turn on. I need to fix that.

>>923417
Huh. It's very possible that one of those resistors blew out but the real question is what other component failed that caused excessive current through the resistor b/c its unlikely it would fail on its own.

>>923422
Did all 7 fail at the same time and do they all have those scorch marks in the same place?

>>923422
We did have some pretty big thunder storms awhile ago and that broke a bunch of peoples electronics, maybe that sent a surge or something through the wires.
>>923423
They do not all have scorch marks in the same place. I think this was the only one that had those scorch marks. There's more than 7 of them, it's just these 7 are not working, and they are on different floors in different buildings. I have no idea when they failed, because the only people that check them would be the fire Marshall and me when I randomly decided to check them a little while ago. There's other people working here who should have been checking them.

>>923426
Well I'd say if they had scorch marks in the same place and didn't all fail at the same time it's probably some weak-link component that's just reached the end of it's life expectancy and failed in all of them, but since they didn't I'd say the thunderstorm is a good probability and it could have caused all of them to fail in different ways which would be a major pain in the ass to fix. If there's any working ones that fail within a few months then my first theory is probably right and they're about the same age and failing the same way.

>>923430
The ones that did fail are all about the same age, same model. Some of the working ones are the same age and model, some of them aren't. I suppose it's just getting near the end of their life expectancy. Any recommendations?

>>923433
Unless you know someone who can actually do diagnostics irl you should probably just buy new ones. Its tough to fix this kind of shit over the internet.

>>923434
Now the next challenge will be figuring out how to wire the new ones in

>>922931
The answer is always LTSpice

>>922134
question: how good are you at math? if you're doing anything more than simply soldering pieces together that you're given, you'll need some math skills and know ohm's law, how all of the electronics work (what the difference between a photoresistor and a photodiode is) etc., how to use a breadboard to create a circuit, and all sorts of symbols for circuit diagrams. apply to this job with caution, they might be expecting a lot more than you expected. Inquire what they mean by "experience with simple electronics." All the stuff mentioned above is easy to learn online, it just takes time and focus. I recommend afrotechmods on YouTube. he doesn't have a series Hut rather random videos of varying difficulty, but he explains everything very well.

>>923446
how do you pan the fucking view in ltspice

I have a 6V buzzer - the constant pitch kind, with a built in oscillator I guess. If you tap it, some element inside vibrates at its predetermined pitch.

I don't know the exact name of it, but my question is, is it an inductive load? Seems like it could be some magnet in there.

>>923482
No it isn't, I've used them too. No flyback diode needed.

>>923484
Good. Too late now even if it was. In my bid to put my basic electronics skills to practical use I made a "tea timer" based on a 555 monostable that sounds a buzzer after 4 and a half minutes. Had to snake 4 resistors in series to make the right impedance for the 470uf cap.

It runs off 3 AAA batteries at the moment, which is only 4.5v but it seems okay. If I changed it to 6v would I have to bother changing the 220 ohm resistors on each of the LEDs?

>>923387
I get the idea behind this, but wouldn't it be easier for him to just measure current given a resistive load? Surely the meter can't fuck the result up to a scale of 100 Ohms, or is there any problem I'm not considering here?

Anyone here work in radio? I've been looking at going to school to become a radio technician because I like radio but I also want to work rurally - if I could get a job putting up towers for the forest service in the middle of nowhere while living out of a van, that would be fine by me.

>>923559
you should live in a shipping container instead

>>923560
But then I would miss the scenery.

File: 12v-185rpm-20-1-gear-motor-encoder-1-large[1].jpg (150KB, 736x570px) Image search: [Google]

150KB, 736x570px

For motors with encoders, do the encoders work when the motor is spinning at the maximum rpm on the spec sheet?

It seems way too fast for the encoder to not skip especially since the encoder is on the motor itself not the output shaft which may have a lower rpm than the motor itself due to gears to increase torque.

>>923639
Phototransistor and Hall effect sensor used in encoders have extremely fast response times. It's unlikely you can run a motor fast enough for them to not react properly, and it would be a major design flaw if you could.

A more common failure point is the microcontroller reading the encoder. If it's a polling system then the Nyquist–Shannon sampling theorem comes into effect. If the motor spins with a max RPM is 20,000 then the encoder needs to be read 40,000 times a minute. If you want to be able to tell the direction the motor is spinning based only on the encoder output it becomes 80,000 times a minute.

>>923639
> For motors with encoders, do the encoders work when the motor is spinning at the maximum rpm on the spec sheet?
Yes, unless stated otherwise.

> It seems way too fast for the encoder to not skip especially since the encoder is on the motor itself not the output shaft which may have a lower rpm than the motor itself due to gears to increase torque.
If it's an absolute encoder, it will be on the output shaft. A relative encoder could be either; but one that's on the motor itself doesn't need high resolution (i.e. more than one or two pulses per revolution).

>>922310
As a guy who has a job where I'm a technician who deals with soldering SMD and has been asked before "why are your hands shaking", SMDs aren't too bad. You just need time to work with them.

I'd suggest showing them an example of your soldering. The company I worked for actually tested me in how fast/accurate my soldering was with a small 6-pin thruhole connector on a dummy board. Depending if they use BGA's or small processors, they may have a hot-air rework machine to help replace those.

What would be more important is to show you understand the simple electronics, and troubleshooting. Talk about how you can understand what typically will cause LEDs to fail in a circuit, draw circuits to explain/show you can read schematics, maybe even draw block diagrams to show how the accelerometers are making the saber make an appropriate woosh sound.

I honestly have started to hate my job due to its monotony and have an interview for a radio company but I'd think I'd hate it a lot less if I was repairing lightsabers.

>>923665
https://www.youtube.com/watch?v=b9FC9fAlfQE

Forgot this, some people don't like this guy in /ohm/ but he has good tips in soldering at least.

>>923027

It turned out there is a bad capacitor on my motherboard. My cat pissed on my box some 8 years ago and I never noticed because I had a 360 by then. It's a 1 farad supercapacitor oddly enough but it's attached to a bunch of elements labeled as CR. I don't know what they do.

>>923686

my understanding is that the supercap is used to provide power to the clock chip so it keeps time even when the unit is unplugged. these caps all fail eventually, but the units keep working anyway.

>>923482
>>923485
There's a slight "bug" in my circuit. There are 2 LEDs, one that goes on with the buzzer, and one that goes on when the buzzer is off (sinking and sourcing respectively).

The buzzer is also sinking into the output pin of the 555. Thing is, when the buzzer goes off, the sourcing LED flickers faintly. It stops when I flip the buzzer enable switch.

>>923691
There's a supercap in an xbox? Can you make some stun or rail gun with it?

>>922117
everything you need to know - hands down the best soldering video out there
PRO TIP watch all the 3 parts
https://youtu.be/J5Sb21qbpEQ

>>923801
Supercaps are usually high in Farads, but something in the ballpark of 5v. That's not ideal for a stun gun.

>>923703
Anyone know why this is? Some kind of residual voltage from the buzzer?

>>923823
Is this an electromagnetic buzzer? You should try adding a snubber diode.

File: image.jpg (1MB, 4032x1808px) Image search: [Google]

1MB, 4032x1808px

Got a solder kit for Xmas and got working on it today. Struggling. How long did it take you all to get decent at it? Pic related, my first attempts.

>>923826
The one on the far left is pretty good, but with the other ones it looks like you're not touching the iron to the pad before applying solder.

>>923825
Yeah I expect it is. It's a fairly heavy little module with a decent sized vibrating thing inside. Someone else said it wasn't an inductive load though.

Funny thing is, I added a diode on the breadboard and it seemed to stop it, then it started doing it again so I left the diode out when making the circuit board. Must have been in the wrong place.

Should I put it between the 555 out pin and the buzzer? I think that's where I put it on the breadboard version but it was late and I was stoned so who knows...

>>923832
A snubber diode goes in parallel with an inductor, but with the negative end of the diode pointed towards VCC. When you cut power to an inductive load the energy stored in the coil's magnetic field flows out in reverse. The purpose of the snubber is to short this.

>>923826
Not enough heat or you are not keeping your soldering iron there long enough. Maybe allow for a little more solder to flow onto the joint too.

Can you take a well lite photo of your soldering iron's tip? I would like to check for oxidation.

>>923703
Do you have adequate decoupling capacitors directly across the supply pins of the IC?

File: image.jpg (2MB, 4032x3024px) Image search: [Google]

2MB, 4032x3024px

>>923835
Sure. Shouldn't be too bad though given I just got it. Sorry I couldn't get a closer up shot, phone won't focus and closer up.

File: image.jpg (1MB, 2507x4032px) Image search: [Google]

1MB, 2507x4032px

>>923845
Other angle.

File: dry_tip_cleaner_main.jpg (32KB, 358x324px) Image search: [Google]

32KB, 358x324px

>>923847
Doesn't look too bad but oxidation naturally happens to every iron.

Have you got a brass wool pot for keeping it clean? The tip should be able to take a tin (coating of solder) by just wicking it with fresh solder.

I'll post another photo showing what the tip should look like but I think those joints just needed longer with the heat plus more solder.

File: tinned_tip.jpg (13KB, 300x222px) Image search: [Google]

13KB, 300x222px

>>923847
>>923849

It doesn't have to be 100% spotless but it should retain a coating of solder, this helps transfer heat to the joint quicker. Next time you heat it up wrap some 60/40 sn pb solder (not lead free) around the tip so it will melt to it as it heats.

>>923839
No, I forgot to. I did it on the last 555 circuit I did though, but I thought it was in case of a dodgy power supply or something. This is AA battery powered.

Is it more important than that? Would it make any difference here?

>>923834
As in a flyback diode? I'm not sure if it is an inductive load yet. It probably is though right? It takes a set voltage and emits a constant pitch, which doesn't change much with voltage. It takes care of its own oscillation.

This flickering happens all the time that the buzzer is sounding (not just when you remove power).

>>923826
Funnily enough I just filed the tip of my iron so there's more of a flat pad on the underside to heat the copper tracks properly. I haven't tried it out yet but I was having the same problem as you.

>>923857
Filing a soldering iron tip is a bad idea, it just removes the plating and makes the problem come back even worse next time.

>>923858
I made sure to heat it up and wet the end straight after. It's only a cheap thing anyway and the tip was a mess.

File: maxresdefault.jpg (111KB, 1280x720px) Image search: [Google]

111KB, 1280x720px

>>923855
All IC's need decoupling capacitors in most cases for stability. The internal impedance of the battery's and power cables cause high frequency "dips" in the supply voltage rails every time the IC changes state that you can't detect with a multi meter.

The average current of the circuit is very low but when the 555 timer switches very fast it needs high current spikes for maybe a few nanoseconds, this + parasitic wire inductance/resistance and battery internal resistance is what causes the voltage drops.

A 100nf+10uF very close to the supply pins of the 555 timer will remove these spikes and prevent unwanted oscillations/false triggering.

https://www.youtube.com/watch?v=VfCu-siq0-Y

tl;dr place a 100 nanofarad (code 104) ceramic capacitor across pins 1 and 8 of the 555 timer and be sure to keep them physically within 1cm of the chip. Adding a further electrolytic of a few tens of microfarads will all but eliminate any voltage spikes.

>>923849
>>923851
I've just been using a simple sponge that came with the kit. Additionally, it only came with lead free solder, which when I tried to tin the tip a bit it doesn't want to stick. This is the thing I got: http://www.microcenter.com/product/431761/Deluxe_Learn_to_Solder_Kit I need to make a stop by the hardware store anyways, so I'll see if they have that stuff in stock.

>>923861
Ah ok, well its always good to have a practice iron to learn on rather than messing up an expensive soldering station.

>>923865
Fair enough. I had the foresight to use a DIP socket instead of soldering the IC straight to the board (even though I ended up soldering it in the wrong way), so I can probably just squeeze it in.

>>923867
Have you dampened the sponge with water? If not you should, you don't want it soaking wet but just damp enough for it to be an effective wipe.

But anyway the wool is much better than the sponges and I would definitely recommend one, I give my tip a dip after every 10 joints or so.

If it still won't take a tin then this is the chemical way of doing things with a tip tinner pot http://www.amazon.com/Thermaltronics-TMT-TC-2-Tinner-0-8oz-Container/dp/B00NS4J6BY

It seems quite expensive for such a small tin but it never seems to run out, I used this method when a new tip for my iron make solder ball up and fall onto the bench.
This guy has some good how-to's on the subject too https://www.youtube.com/watch?v=cB64dkcYcHE

>lead free solder
Its doable with lead free but certainly not as easy as with the leaded stuff (60/40 sn pb is my favorite blend and the most common). Manufacturers generally give away lead free solder as they get tax breaks for being green.

>>923874
It didn't make any difference. I didn't think it would but I suppose it's good practice.

This flickering has to be something to do with the buzzer. It seems to be flickering in time with the buzzer but I'd have to get the oscilloscope on it to verify that.

>>923874
The good thing about the 555 timer's pin out is that the supply pins (1 and 8) are right next to each other so you could always tack the 100nF capacitor on the underside of the board. Its not as mechanically sound as correctly putting it through the holes of a PCB but for one off projects its fine.

As for the larger electrolytic capacitor that can be a bit further away if layout is a problem, just as long as the 100nF is practically kissing the 555 timer.

>>923879
Can you post a circuit schematic?

File: SDC10923.jpg (707KB, 2048x1536px) Image search: [Google]

707KB, 2048x1536px

>>923881

>>923883
Cap across IC is actually 100nF.

>>923883
R1 = 470k? Also what are R3 and 4?

>>923887
Lol yeah, um I wanted a 4.5 minute delay so I worked out the resistance required for a 470uF cap, then composed an approximation from 4 series resistors.

It gave a delay of about 5 mins. I'm assuming that's down to the tolerance of the cap. Anyway, I scaled down the resistance accordingly and came up with around 454,700, which I, again, composed from 4 series resistors.

It never occurred to me that I could have just used a 470k one, I was so engrossed. Oh well, it's as accurate as I could achieve with my inventory (about 4:32).

So yeah it's a compound resistance of 2x220k, 10k and 4.7k.

The LED ones are 220.

File: 18034[1].jpg (15KB, 290x250px) Image search: [Google]

15KB, 290x250px

>>923889
This is the buzzer. It's a Velleman SVM06 SOLID-STATE BUZZER.

>>923883
I'm just building the circuit up, which LED is the one with the flashing problem?

>>923893
The sourcing one.

File: NE555EQUIVCCT.gif (16KB, 832x380px) Image search: [Google]

16KB, 832x380px

>>923896
Try this, two reverse biased diodes and a small capacitor (few tens of nF) across the output pin. Some of these buzzers are basically relays that oscillate by making and braking their own contacts.

Sorry for the shit paint-cad drawing. Diodes can be any type such as 1n400x,uf400x 1n4148 series etc.

>>923902
>Some of these buzzers are basically relays that oscillate by making and braking their own contacts.
I thought it would be something like that.

It's gonna be a bit tricky making that mod now but I'll consider it, thanks.

The flickering isn't a deal breaker, as such but it would be nice to eliminate it.

>>923896
Is that the bottom LED paired with R4?

>>923906
Yes.

>>923907
Does the flickering go away if you disconnect one leg of the buzzer from the circuit leaving just the LED's to light up?

>>923910
Yes. There's a switch that does just that.

File: circuit.jpg (112KB, 404x430px) Image search: [Google]

112KB, 404x430px

>>923912
>>923910
In fact here's the circuit in all its glory!

>>923912
Ok, well that's good and means the circuit you built is correct. The top diode across the buzzer here >>923902 is the steering diode, or flyback diode which takes care of most of the back emf.

The capacitor is to help slow down the rate of rise of the voltage spike, since diodes have a small amount of time before they conduct. The lower diode recycles this stored energy back to the input decoupling capacitor and adds added reverse voltage protection to the 555 timers internal output stage.

The LED coming on could be caused by two things in this case. Its either being directly powered by the energy stored in the buzzers inductance (like a boost converter), or its the voltage spike causing the 555 timer to misbehave when the spike appears on the output pin.

tl;dr the two protection diodes on the output + small capacitor should fix it.

>>923918
Nice and neat anon, I like it.

>>923918

oh shit, dude, that's a mechanical buzzer, which is 19-th century technology. it's pretty much false advertising to call it ''solid state''.

>>923932
Isn't it the same thing as they use in car horns?

>>923930
>The lower diode recycles this stored energy back to the input decoupling capacitor
Which cap? I don't see the role of the lower diode.

File: ne555.png (39KB, 688x388px) Image search: [Google]

39KB, 688x388px

>>923918
Is your battery's voltage sagging once the load of the buzzer comes on?

According the datasheet for the ST version of the NE555 4.5v is the minimum voltage it can run on, so it could indicate the chip going into an unstable state when the supply voltage drops below this.

http://www.st.com/web/en/resource/technical/document/datasheet/CD00000479.pdf

>>923931
Cheers. It's only my third circuit board. I like to put a lot into the prep though. I printed out some blank "veroboards" I made in Corel Draw and I do at least 2 drafts on that (and work out where to cut the tracks, etc), after the whiteboard before I make it for real.

>>923933
I wouldn't have thought so. Unless you mean loosely based on the same principle.

>>923936
>Is your battery's voltage sagging once the load of the buzzer comes on?
Yes. The yellow LED dims slightly. I'm currently running it off 3 AA batteries, so I'm pushing my luck, yeah.

If I upped it to 4 batteries, would I need to up the resistance to the LEDs?

File: 1451776208373.gif (18KB, 832x380px) Image search: [Google]

18KB, 832x380px

>>923935
The cap in the red box. The lower diode is extra insurance, the top one is the critical one.

Most modern IC's have output stages with the two protection diodes these days, its to prevent the output pin from ringing negative.

>>923941
>The cap in the red box. The lower diode is extra insurance, the top one is the critical one.
Ah so you do mean that one. Wasn't sure. I don't really see what it does still. I understand the basic idea of the flyback diode though.

I'd have thought the buzzer would have some kind of protection built in.

>>923939
>If I upped it to 4 batteries, would I need to up the resistance to the LEDs?

Nah you'll be fine, 220 ohm at the current supply voltage gives you plenty of room for margin. They are probably running at a few milliamps tops with those 220 ohm resistors, so changing from 4.5 to 6v will not increase the current much.

>>923936
>>923939
>If I upped it to 4 batteries, would I need to up the resistance to the LEDs?

I just tried it briefly and it made no difference.

File: ATmega328P.ESD.gif (7KB, 400x237px) Image search: [Google]

7KB, 400x237px

>>923942
>I'd have thought the buzzer would have some kind of protection built in.

It may not be enough to stop the 555 timer from misbehaving, this is where the small capacitor comes in just in case. Capacitors resist changes in voltage, this works in tandem with the top diode which has a small "delay" of a few ns before it conducts.

>>923946
To the flashing or LED brightness?

>>923948
Flashing. It made them brighter though yeah.

>>923947
>which has a small "delay" of a few ns before it conducts.
Is that while it's under the forward bias voltage?

>>923949
Ok, well then its probably being caused by the inductive spiking on pin 3 from the buzzer. Next step is to try a flyback diode across the buzzer, you could just solder it directly across the buzzer connecting wires on the bottom side of the PCB.

If that is still not enough add the extra (lower) diode and capacitor.

>>923950
Its when the junction switches from being reverse biased to forward biased, its more of a physics thing though.

http://web.iitd.ac.in/~shouri/eel201/tuts/diode_switch.pdf

File: osc.jpg (206KB, 1280x1024px) Image search: [Google]

206KB, 1280x1024px

>>923952
There's room on the PCB to put all the extra components on. I'll probably do it tomorrow though.

Here's a pic of the voltage across the buzzer (yellow) and the offending LED (green). I inverted the yellow channel because I had to put the ground clip on the positive side (there was no room to do it the other way around) so this is the correct reading, right?

Should they be mirror images?

>>923964
>I inverted the yellow channel because I had to put the ground clip on the positive side

Shouldn't that have created a short because the grounds on both scope channels are grounded at the scope.

>>923965
Seemed to work fine. I thought it was just measuring the difference between the probe and clip.

>>923964
Hmm that's helpful, can you take one more shot with the buzzer disconnected? It looks like the 555 timer might be doing some kind of false triggering, possible needed some more decoupling capacitance.

>>923967
If you mean switch the buzzer off, that shows a 147mV DC voltage across the red LED and -147mV DC across the buzzer.

>>923966
It does but both ground clips are connected together in the scope for earthing/mains grounding. unintentional loops can be accidentally created if the ground clips are connected to different points in the circuit (unless isolated).

>>923971
Is that with the 555 timer running (LED's flashing) but buzzer switch in the off position?

>>923977
When I press the button to ground the trigger, the out pin goes high, the red LED shows about 2v+, while the buzzer shows 2v-.

The buzzer is off at this point as it's sinking into it, but it's also connected to the supply via the switch.

The screenshot you see of the oscilloscope is in the state where the buzzer is connected via the switch and the 555 output is low, allowing the buzzer to sink. The red LED should not be in action at this point but we see the voltage in green.

I just noticed that the red LED doesn't flicker when the scope's ground is clipped to it, yet the fluctuations are clearly visible in the graph.

File: circut2.jpg (114KB, 404x430px) Image search: [Google]

114KB, 404x430px

To be clearer what I've done here's my attempt at a diagram. For the green, the point is hooked onto the positive leg of the red LED, while the ground clip is actually gripped onto the leg of the 220 ohm resistor next to it.

While for the yellow, the probe is hooked to the negative leg of the yellow LED, which is essentially the negative lead to the buzzer too. The ground clip is on the switch's positive leg, which again, is basically the positive lead of the buzzer.

Then I inverted the yellow channel on the software. Is this correct?

>>923985
With the 555 timer removed from the socket but the buzzer switch set to the on position does the bottom LED light up at all (battery's connected obviously)?

Maybe when the buzzer is meant to be off its still sinking a small amount of current from vcc and into the lower LED but its not enough to trigger the internal buzzer oscillator.

>>923991
They both light up. When I turn on the buzzer switch the red (bottom) gets slightly brighter and the yellow slightly dimmer.

>>923996
The buzzer doesn't go on in either case though. I guess that with the out pin's sinking capability gone, the buzzer can only get its power by going through both LED resistors (which is not sufficient).

>>923999
Actually I think it's just R4 it's going through but that's the explanation right?

File: 01821x01.png (38KB, 458x362px) Image search: [Google]

38KB, 458x362px

>>923996
I think this is the cause now, measure the resistance across the buzzer with the switch turned off (open).

It will be the resistance of its internal coil and this resistance is allowing current to flow through the bottom resistor when ever its connected.

File: 53d65174d91839dda1afb946cde91990558faf88_large.jpg (39KB, 600x600px) Image search: [Google]

39KB, 600x600px

>>924001
Shit wrong image, this is the right one.

>>924001
How does that happen? Isn't the output pin essentially a path to ground when sinking? Does it have a significant impedance?

>>923433
If the bulbs work and you are confident that the batteries are fine then try changing all the capacitors in the circuit one by one, and resoldering any connectors

File: anon2.png (14KB, 688x398px) Image search: [Google]

14KB, 688x398px

>>924007
Not if the buzzer is causing the chip to misbehave, it could be making the output turn off again which allows a small amount of current to flow through the buzzer coil resistance but not enough to trigger the buzzer its self. The wavy waveforms here >>923964 suggest this.

Give this a try first.

File: anons.png (15KB, 688x388px) Image search: [Google]

15KB, 688x388px

>>924017
But that will not prevent current from flowing though the coil resistance and into the lower resistor and LED. To prevent that you'd need something like this.

>>923822

This particular one is 1 farad but only 2.5 volts.

http://www.mouser.com/ds/2/87/Bus_Elx_DS_4376_HV_Series-335924.pdf

This is what I replaced it with. It is very similar except the original part had an ESR of 400 mΩ instead of the 150 mΩ this one is rated for. I don't think this will be an issue though.

>>924018
I haven't done much with transistors yet. Seems like a bitch working out all those numbers. Plus I only have NPN ones.

Now I've got a multimeter and oscilloscope, now's the time to familiarise myself with the nuts and bolts though.

>>924018
>>924193
But I remember last night, the problem went away when I had the oscilloscope on the circuit. The probe on this LED was the right way round but the other one had the ground clip on the positive, so what's going on there?

The circuit functioned so I couldn't have been shorting it, but it seemed to "suck up" that excess current from the buzzer.

File: Screen Shot 2016-01-03 at 8.17.16 AM.png (131KB, 685x567px) Image search: [Google]

131KB, 685x567px

using a mac, ftdi ft232h breakout board, a bosh bme280, and silicon labs si5351a.

when using i2c with pull-up resistors anywhere from 4k7 to1k, the bosch sensor works fine. doesn't skip a beat no matter how fast or slow i set the serial clock.

the si5351a however, reads registers just fine, but when writing a value to a given register, it will sometimes give a response other than ACK. when the clock is slower, it seems to make it worse. i can dump all the registers just fine, but when i try to write a value to the si5351a's registers, it fails intermittently.

what am i missing?

>>924208
how do you generate the I2C clock with this setup?

Why is it that capacitors always seem to be what goes bad?

How can I /gitgud/ at repairing electronics stuff so I can do it freelance while I finish college?

How does a decoupling capacitor work by sending high frequencies to ground when 1/jwC = 1/ infinity at high frequency?

>>924211
with the ft232h

>>924212
>Why is it that capacitors always seem to be what goes bad?

because you're not playing with motors

>>924212
>How does a decoupling capacitor work by sending high frequencies to ground when 1/jwC = 1/ infinity at high frequency?
You just said it - 1/jwC, which is the cap's impedance, approaches zero, thus the spikes get easily shunted into the capacitor.
Saying they get sent to ground is a bit misleading.

File: IMAG1255.jpg (177KB, 1280x720px) Image search: [Google]

177KB, 1280x720px

Would anybody happen to know what kind of connector I need for this LCD?
It's 32 pins at 0.8mm pitch. Problem is, the connectors I found don't leave any space for the holes on the sides.
Should I just cut them off?

http://forum.easyelectronics.ru/viewtopic.php?p=401670#p401670

>>924215
I think my problem is that I have trouble understanding why they go through the capacitor when 1/infinity is 0. For some reason that 0 throws me off. When I see 0 I think that means nothing is going through the cap

>>924215
>>924218
FUCK me nevermind. I was thinking in terms of capacitance instead of impedance. An impedance of 0 means a short circuit which would allow all those spikes to pass through.

Thanks for helping me clear that up

>>924216
Oh, so apparently this is meant for soldering directly onto your PCB.
Examples can be found on YouTube.

File: IMG_20160103_130409.jpg (257KB, 1600x1200px) Image search: [Google]

257KB, 1600x1200px

What are these componentes shown in the picture that appear to hace screwdriver slots in color pink, yellow and red? Some kind of precision pots?

>>924302
Intermediate frequency (IF) transformers.
Basically transformers with adjustable inductance. It is common that the cans also include a capacitor or two so that they're in resonance at ~450kHz or 10.7MHz.

>>924305
Thanks a lot

>>923952
> Next step is to try a flyback diode across the buzzer,
That tends to stop buzzers from buzzing. It's better to use a snubber network.

File: touch-pad.jpg (24KB, 458x317px) Image search: [Google]

24KB, 458x317px

hey /ohm/, im trying to make a diy touchpad like those found on laptops, just a simple one that can figure out the x,y location of your finger and send it to a mcu. I understand that moderns ones typically use capacitive sensing, but i am having trouble figuring out what sort of grid of metal shapes i need to make in order to determine the location of a finger.

File: 51U2axKJTnL._SX425_.jpg (31KB, 425x311px) Image search: [Google]

31KB, 425x311px

Sup /ohm/, figured this would be the best place to ask before making a thread.

I'm fairly new to Hobby RC stuff, and I just purchased a battery charger, but the charger [Turnigy Accucel-6 80W 10A Balancer Charger | Purchased from Amazon fyi] doesnt actually come with a power supply.

I was wondering if any of you have any experience with this product and what PSU you would recommend.

I know it needs a xt60 connector as its input, which makes shopping for one pre-made pretty annoying.

I'm not against modding a different supply, but seeing as I'm new, I wanted to get some information before I went further.

Link to Charger: http://smile.amazon.com/Turnigy-Accucel-6-Balancer-Charger-JST-XH/dp/B00T3RKONE/ref=sr_1_7?ie=UTF8&qid=1451858452&sr=8-7&keywords=turnigy+power+supply


Pic is Charger btw.

File: 76186.jpg (134KB, 565x414px) Image search: [Google]

134KB, 565x414px

>>924356
I think it really would just be like a Cartesian Plane of wires. One in the X direction, and another in the Y. All able to individually sense whether or not they're being touched. Then take the average of all the ones being touched and call it the "real" location of the finger on that particular plane.
Also, I'm >>924418

Just wanted to say that after finding someone on YouTube who was able to respond quickly, and he basically said that I should go with something above 12.5A if I wanna get full use of the charger.

However, finding Power Supplies really isn't easy. It seems that this hobby isn't like computers where's there's a million and one products that are all the same, rather I found it very difficult to find something suitable that wasn't over a hundred dollars.

So I ended up getting this "Turnigy Reaktor Pro 240W 16A" from HobbyKing. Which I really didn't to do because I knew the shipping would be retarded levels of expensive. So it effectively went from a 31usd psu to 57usd after shipping. And its gonna take 1-2 weeks.

I guess I'll also have to buy the XT60 adapter for it as well, but luckily I can just get that on based Amazon.
Thanks for reading my blog. Hope the saga helps someone.

And big ups to David Sunshine on YouTube for the help. His battery comparisons are what originally drew me to him, and he's the source of the info that solved my problem.
His channel: https://www.youtube.com/channel/UCeSmdFQeU7rTXxzhjpPVmlw

And the video that compares 18650 batteries:https://www.youtube.com/watch?v=Wnf0RnXhgjY

File: 02394823.png (365KB, 442x787px) Image search: [Google]

365KB, 442x787px

So these are supposed to be wired into your house, they're the right voltage for my house but how easy would it be to just solder the wires to a normal plug and plug that into the wall? Would that work, I don't really want to go fucking around with mains power.

Alternatively how would I go about converting this to DC, just seems a lot simpler and safer

How do I calibrate an analogue multimeter? I blew the 500mA fuse and just bypassed it. Then, obviously, I ended up hooking it up to a voltage source in current mode. For less than a second, but still, it's measuring 2v for brand new 1.5v batteries now. It was never the most accurate, but I'm sure it wasn't this bad.

Have I fucked it up?

>>924474
- open it up, usually has adjustment potis - leastways, old school models did.

>>924490
I don't remember seeing any when I bypassed the fuse. I'll have a look anyway. Probably should buy a pack of fuses for it anyway...

>>924418
Have you got any spare atx power supplies laying around?

You can jumper the green wire to any of the blacks and it will power up outside of the PC, the 12v rail can typically supply tens of amps with very little ripple.

Just be sure to add dummy small loads to the 3.3v and 5v rails, a resistor dissipating a few watts will be ample.

>>924504
Add small dummy loads*

>>922399
>go be an electrician if you like circuits and instrumentation

I think the job that is more closely related to this thread is electrical engineer.

>>922117
Trying to build custom heating elements where is the best place to get resistance wire?

File: Tesla_Batteries.jpg (148KB, 1280x720px) Image search: [Google]

148KB, 1280x720px

>>923326
>I've been told I need a shit load of batteries to do DIY electricity generation stuff. Is this a shit load?

No. You need a shit load of batteries for storage... of said generated electricity...

Batteries have voltages, test for Direct Current Voltages... do not kill yourself... ( rethink this though...)

>>924797
Toaster

I have a set of old woofers. I want to get them working off a transistor as a little tutorial to understand transistors better.

They're 4ohm and 30W, so assuming that's RMS V= sqrt(P x R) = sqrt (120) = 10.9544511501V RMS.

Multiply by sqrt(2) to give 15.49 max peak voltage. Let's say 15 for simplicity.

So the transistor to power it would need a collector current of 15v/4 ohms = 3.75A, or let's say 4A.

Is this correct?

>>924861
>I want to get them working off a transistor
Obviously I realise I'll need 2 separate ones.

File: lord nikon.jpg (82KB, 800x600px) Image search: [Google]

82KB, 800x600px

>>922117
>What? Did your mom buy you a 'duino for Christmas?

I built a desk in my room and I want to plug my monitor, lamp and computer to a power bar which would be on the floor but I want to have a button that I can attach under the desk so that I can turn on/off that power bar without needing to go under my desk every time. What are my options?

My USB oscilloscope is confusing me. It's supposed to take up to 35v but when I apply a DC voltage, as I turn up the knob, the line rises up until it reaches 5v then freezes. I should be able to measure DC with it, right?

Also it's for up to 20mhz but in the corner of the screen, the software says sample rate: 1mhz, so I can only measure up to 500khz.

Not that I need to go that high but still...

>>924862
In that case it's correct.
Note that the 30W rating is for sine and if you drive the amp with square wave (or overdrive it), the output power will be twice as high.
It would probably make sense to start from a smaller amplifier, if you're going to design it by yourself. Even more so, if you're going to use discrete semiconductors only.

>>924919
It is possible to build a 20MHz oscilloscope which samples only at 1MHz, but you're pretty much limited to repetitive waveforms. It is/was a pretty common approach in very fast oscilloscopes. (Yeah, it's still shit.)
Dunno about your input range problem. Maybe your scope is expecting a 10:1 probe?

>>924504
>>924505
I actually do have a few. But I decided to just get this thing as an investment.

Thanks for the advice tho anon.

>>924929
>Dunno about your input range problem. Maybe your scope is expecting a 10:1 probe?
No I've checked the switch. It's doing the same thing with the output of a 555 astable as well so not just DC.

>>922314
Google "nichrome wire"

>>924462

you can do that, convert a wall lamp into a plug-in lamp, but you shouldnt need to do that just coz you're a scaredy cat afraid of 120 volts. 120V is child's play. you feel a mild tingle, at worst. stop being a girly boy, and wire it up properly.

If I use a transistor to amplify a signal, which peaks at a certain voltage, I use a resistor between that and the base, right?

This makes a certain current flow into the base, causing a certain current to flow between collector and emitter, is that correct?

My query is, then, given that whatever I plugged that into would (presumably) be a voltage controlled input, how do I "translate" the current created into a voltage?

Do I put a resistor in there somewhere and get the voltage across that?

>>924915
Look at smart plugs, you can get them with remote controls. They go between the wall outlet and power bar, basically a remotely operated switch.

>>924915
>>924963
These http://www.amazon.co.uk/Status-SREMSOC3PK3-Remote-Control-Socket/dp/B003XOXAVG

More expensive versions can be controlled with a smart phone.

File: backlight.png (52KB, 915x1050px) Image search: [Google]

52KB, 915x1050px

I've taken apart an old laptop to use the screen as a light. Unfortunately it uses a CCFL backlight which complicates the process.

I've watched this tutorial: https://www.youtube.com/watch?v=QQCI0M-ZeRM

The inverters they use seem to have 4 pins but mine has 9. I can't seem to find the spec sheet for it (product#: E-P1-50056)

I'd rather not just try every combination of pins to see which works and I'm just thinking I can get a generic one like they have in the video.

I've found some (https://www.digikey.com/product-search/en/optoelectronics/inverters/524345?k=inverter) but there's way too many for me to choose from. I tried looking up the spec sheet for the monitor itself (Samsung LTN141X7-L06) and found this (pic related) but it doesn't tell me what output voltage I should be using.

How do I figure out which inverter to get?

File: Soldered-fuse-and-wire-fuse-in-an-830B-multimeter.jpg (34KB, 400x234px) Image search: [Google]

34KB, 400x234px

>>924474
It's most likely fine, multimeters measure current by using an internal current shunt resistor of about 0.1 ohms. It converts the voltage across this internal resistor to current by using ohms law.

2 volts across 0.1 ohm means that about 20 amps must have been flowing. The component labeled 2 is the current sense resistor.

Im trying to make a sine wave with a 555, by filtering the square wave output. I worked out the RCs for a lowpass cutoff at around the frequency of that square wave. I wasn't expecting a perfect sine wave (maybe more like a triangle due to the low steepness of the cutoff) but I got something different altogether. Some sort of ramp type thing. It looked more like a graph of the voltage at the timing capacitor, but with a different offset.

I even did some filtering on a square wave at different settings on a wave editor to see what effect it had on the wave, but I got nothing like the output I got on the circuit.

>>924966
What is the make and model number of the laptop? I might be able to find a pinout.

>>924969
But still I think I must have done something if it now says 2v for a 1.5v battery. I don't think it did that before.

It was only about 7v when I accidentally connected it in current mode. As I say, I blew the 500mA fuse before and bypassed it before making the same mistake again.

If it had a 500mA fuse in it, then how much current would the components in the multimeter be able to take? Probably more than 500mA for safety reasons or whatever but how much more?

>>924970
Also, the waveform wasn't symmetrical about the vertical axis (as are square and triangle waves), so doesn't that mean even harmonics have got in there somehow?

File: calibration-xl830l.jpg (113KB, 521x428px) Image search: [Google]

113KB, 521x428px

>>924974
The calibration pot looks like this, if there are multiple ones then find the voltage adjustment by slowly turning it and seeing if the voltage readout changes. If nothing happens then move it back and go onto the next one.

>>924972
It's a Toshiba Satellite 2400
Model Number: PS240C-00UJXP

>>924977
I don't remember seeing any pots inside it but I'll have a look again. There's a pot on the outside but that's just for measuring resistance.

File: ector.png (45KB, 581x565px) Image search: [Google]

45KB, 581x565px

>>924979
Sorry anon but I'm having no luck finding a diagram. If you can find out the ODM of this laptop such as wistron spears, quanta compal etc them it might lead you to finding a schematic.

The closest match I got is for a drop in replacement model http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/HBL-0243.pdf

Can you get a close up picture of the connector? As I suspect a few of the pins are actually in parallel and only count as one electrical pin in the diagram.

>>924966
Can you post a link to that datasheet in your image?

>>924980
Could be on the reverse side of the board?

>>922138
>capaciter
"yer hired"

>>922404
mirin that hakko

>>923826
not enough solder imo, I tend to add enough so that the pad is covered by a thin layer...you don't want a huge glob of it, but making sure you get a good bond prevents cracked solder joints down the line. Just make sure you put your heatsink clip on any sensitive components.

File: tumblr_mye22tbtHQ1qbcb48o1_250[1].gif (235KB, 250x117px) Image search: [Google]

235KB, 250x117px

>>925015
Get back in there and do something to do with capacitaters.

>>925002
Shit that's not right either, HBL-0275 is the correct drop in replacement.

All I can suggest is that not all of the pin are needed just to make it light up, find VCC and ground and then maybe a power on and dimming signal. These can be pulled up to a couple volts via a 10k resistor.

If all else fails you can get cheap CCFL laptop inverters on ebay

>>924970
Maybe the capacitors are not large enough for the load impedance?

>>925005
http://html.alldatasheet.com/html-pdf/106605/SAMSUNG/LTN141X/1494/5/LTN141X.html
It's not the exact model, but it's the closest I could find.

>>925002
I see 5 contact points on the back, and while I'm no expert, it looks like you may be right. Here's a view of it:
http://imgur.com/a/phjtZ
>>925020
>If all else fails you can get cheap CCFL laptop inverters on ebay
That's exactly what I was trying to do, but I need to know which to buy.

https://www.digikey.com/product-search/en/optoelectronics/inverters/524345?k=inverter

File: conecctor.png (348KB, 449x354px) Image search: [Google]

348KB, 449x354px

>>925022
These three pins look like they might be connected together so its probably one of the supply connectors, given the fuse they lead to I think its the positive rail.

Can you still connect it to the laptop and measure voltages whilst the screen is turned on?

File: invertet.png (49KB, 698x469px) Image search: [Google]

49KB, 698x469px

>>925022
This is from a Philips inverter (SEM SIC-130T) designed to go with that display's lamp.

>>925021

In what sense? Do you mean I should get the same RC constant with a bigger cap and smaller resistors?

What is happening here then? Is my cap filling too soon or something? I tried bigger ones but they just squashed that same waveform down.

File: other.png (50KB, 659x569px) Image search: [Google]

50KB, 659x569px

>>925041
>>925036
Found the pinout for a similar inverter but YMMV.

File: waveform-exp.png (10KB, 719x398px) Image search: [Google]

10KB, 719x398px

>>924970
>>924976
If you feed a square wave to an R-C filter, you get exponential rise/fall (pic related).

When the output voltage is zero, the current through the resistor (and thus the rate of change of the capacitor voltage) is proportional to the capacitor voltage.

dVc/dt = -Vc/RC
Vc(t=0) = Vout
=> Vc = Vout*e^(-t/RC).

More generally, the current through the resistor is proportional to the difference between the output voltage and the capacitor voltage.

dVc/dt = Vout-Vc/RC
Vc(t=0) = 0
=> Vc = Vout*(1-e^(-t/RC))

In terms of the frequency domain, an RC filter isn't a very good filter. Gain is inversely proportional to frequency, so the third harmonic will be present at 1/3 of the level of the fundamental, the fifth at 1/5, etc. This corresponds to a roll-off of -3dB per octave. Also, the phase shift varies with frequency, which is why the result doesn't look like summing sin(n*x)/n.

To get something resembling a pure sine wave, you'd need a much faster roll-off, e.g. a multi-stage Sallen-Key filter or a tuned LC filter.

>>925047
What is your intended load anon?

>>925036
The laptop doesn't work, which is why I took it apart.
I got it from a friend who said it just stopped booting, but the screen should still work.

>>925041
So then I should be looking for something that outputs 1200V with ~6mAmps, right?
Would something like this work: https://www.digikey.com/product-detail/en/CXA-0543/445-5394-ND/2346009

>>924958
Your general idea is correct. You would put a resistor between the collector and the supply voltage. This is a common-emitter configuration.

However: the main problem with this is that the gain varies with the transistor's current gain (h[fe]), and h[fe] varies with temperature and frequency.

To get around this, you need to use negative feedback to stabilise the circuit. This is normally done by putting a resistor between the emitter and ground (emitter-follower).

On its own, that gives you a current amplifier with no voltage gain. Any increase in base voltage will cause a corresponding increase in emitter voltage. The emitter voltage will track the base voltage so that Vbe maintains at the transistor's turn-on voltage (~0.7V for silicon). In this configuration, a base resistor isn't necessary; the feedback limits the base current.

To get both stability and voltage gain, you connect resistors to both the emitter and collector. As the same current (well, apart from the base current, which is typically negligible) flows through both, and the emitter voltage tracks the base voltage, the voltage gain is given by the ratio of the collector resistor to the emitter resistor (i.e. it's independent of the transistor's h[fe], provided that the collector resistor isn't so high as to be the limiting factor).

>>925056
Could be the CMOS battery is dead? I had a Toshiba in here recently that would just sit there and the back light didn't come on at all until I replaced the CMOS battery, after that it fired right up and become my gentoo fuck around machine.

>https://www.digikey.com/product-detail/en/CXA-0543/445-5394-ND/2346009
Gosh that's expensive, it will most likely work. Do you intend to power it from an external voltage source and does the inverter need to sit inside of the display bezel? As that one needs about 12v 600mA.

I was thinking of something more in the region of this http://www.ebay.co.uk/itm/Universal-CCFL-Inverter-LCD-Laptop-Monitor-2-Lamp-10-28V-For-10-22-Screen-/191140758671 but I'm not sure that will fit inside the LCD bezel.

File: egay.png (362KB, 1141x435px) Image search: [Google]

362KB, 1141x435px

>>925066
>>925056
This is a better option if in the USA and needs to fit inside the bezel http://www.ebay.co.uk/itm/UNIVERSAL-INVERTER-5V-28V-DC-INPUT-1-Lamp-For-LAPTOP-7-19-CCFL-LCD-MONITOR-6-/251078921946

BigClive has a good video on how to set these up https://www.youtube.com/watch?v=EFGWAyy1gtM I prefer connecting the "adjust" and "on" pads to VCC and Ground via a resistor of about 4.7k, just in case.

File: Untitled.png (805KB, 840x525px) Image search: [Google]

805KB, 840x525px

>>925066
I don't have a spare CMOS battery, and I'm not even sure that's the problem. Honestly though, I'm just going to replace it so I don't want to waste more money than I need to.

Also, I will be using an external power supply. I was just following a video (pic related) and that's what they're doing.
I already have something that works with it (provides 12V .6A) as I was rummaging through my box of cables. I'll just strip the wires and connect solder it onto the board.

>>925069
Those inverters are significantly better for price, though that second one has a $12 postage. I can find something in my area for cheap, I just wanted to make sure that I'm looking for the right one.

Even if it's $2, I'd rather not waste $2 and find out it doesn't work.

File: 20160104_201409.jpg (2MB, 4128x2322px) Image search: [Google]

2MB, 4128x2322px

The DC jack of my stylus broke (pulled it off like an idiot). There are two solder points, anyone know which belongs to which? The circular object in the center is the top of the pen component, which has a DC jack on the other side of it.

>>925077
Show the other side of the DC jack.

File: yessirrrr.jpg (2MB, 4128x2322px) Image search: [Google]

2MB, 4128x2322px

>>925080

>>925082
Is that some sort of powerbank and barrel connector? My guess would be the center pin being positive, use an ohm meter to check for continuity between the solder tag and barrel.

>>925073
>provides 12V .6A
That should be ample, small laptop CCFL's usually draw about 5-6 watts per tube plus any losses in the driver circuit.

>Those inverters are significantly better for price
Yeah don't go spending much money on an inverter if its just for making a light piece. Those digikey units are a blatant rip off in low quantities.

This on seems to have no shipping charge and is cheap, but I am in the UK so it might be calculating it differently http://www.ebay.com/itm/Lcd-monitor-ccfl-1-lamps-universal-inverter-for-laptop-/391340135064?

>>925088
This one*

>>924884
It's cool man, he's elite.

>>925106

pshhhhhh, nothing personal, kid

>>924941
It's 240v where I am and it's being wired on the the front of a cupboard, it'd be easier to get dc behind there than ac

File: 02394923.png (100KB, 330x335px) Image search: [Google]

100KB, 330x335px

>Bought a cheap-o bench power supply
>Arrived today
>Plug it in
>Not plugged into anything else
>5min later it just dies

Did I get a dud or what?

>>925049
If the cut-off frequency of the RC filter is much lower than the frequency of the square wave, you'll get triangle-like output. If you filter the triangle with another RC filter, you'll get sine-like output. The output waveform gets increasingly better (and weaker, of course) as you lower the filter cutoff frequency.

File: Le+_482f0157c9772bb0fc6b55923695d3f0.png (17KB, 274x242px) Image search: [Google]

17KB, 274x242px

>>925248
>cheap-o
>did I get a dud?

>>925255
I still expect it to last more than 5 minutes out of the box

File: Well+meme+d+b0ss+it+ll+be+useful_3666dd_5452135.jpg (65KB, 640x640px) Image search: [Google]

65KB, 640x640px

>>925256
>China export
>I expect

Lol.

>>925258
This.

Had a chinese ebay "5.1" amp in for repair. It had a 2 channel amp with 3 speaker terminals connected to one channel and one to the other. Also contained two concrete blocks in plastic boxes to make it feel heavy.

So what is the warranty on the power supply and does it have free return freight?

>>925265
I contacted them, then sent an email with pictures of it and the postage on the package. Waiting for a reply.

It was from banggood, I've been buying shit from them for years. A bit better than ebay, on ebay you could get any range of quality, on banggood it's always at least one step above terrible.

File: 2016-01-05 10.18.03.jpg (1MB, 2560x1920px) Image search: [Google]

1MB, 2560x1920px

I found an old Russian ('75) analog CRT tube powered oscilloscope. I think it was my grandpas but he might have just had it in for repairs. I plugged it in and I lived to shitopste another day.
Now, these is a small issue however.
The "line" is moved half way to the left and half way up. And after some fiddling with the X and Y position controls i cant get it past this point.
I assume there are calibration trimmers inside but I'm a bit hesitant to open it up since the manual and schismatic are in cyka blyat.
I'll post the schematic, so if someone could point out the pots that are used for X, Y calibration I'd be grateful.

>>925248
Check the fuse.
These things are shit, not precise, but with basic electronics you can nigger them to life

>>925277
I've never seen any kind of device of that sort that was designed by Soviets, and I can't make out what the schematic shows, but I wish you god speed. Would love to see a few pics of the scope itself, never seen a Soviet-design scope before.

>>925278
This, also show pics of the (presumeably) dirty ass internals

File: DSC_7739.jpg (762KB, 3014x2140px) Image search: [Google]

762KB, 3014x2140px

Anyone happen to know what this connector is called (the male one). I need to source a new wall wart for a 12vac lamp but it has this odd little connector, there are no markings indicating what it is.

>>925278
>>925282
I'll see what they say before opening it up, but I'll post pics of shit shoddy internals if I do.

File: DSC_7737.jpg (300KB, 2005x1496px) Image search: [Google]

300KB, 2005x1496px

>>925283

File: 2016-01-04 21.48.30.jpg (1MB, 2560x1920px) Image search: [Google]

1MB, 2560x1920px

>>925280
I've been jacking off to it for a few days now. will dump picks

File: 2016-01-04 21.45.45.jpg (1MB, 2560x1920px) Image search: [Google]

1MB, 2560x1920px

>>925288
Original packaging with Moscow (loosely translated) radio electronics administration stamps.
Even has a passport

>>925288
i came

File: Screenshot from 2016-01-05 20:57:31.png (799KB, 1253x821px) Image search: [Google]

799KB, 1253x821px

>>925283
>>925285

Your welcome.

File: 1376217839586.gif (2MB, 235x240px) Image search: [Google]

2MB, 235x240px

>>925293
THANKYOU!!!

File: 2016-01-05 11.04.56.jpg (1MB, 2560x1920px) Image search: [Google]

1MB, 2560x1920px

>>925290
After some niggering about got it to mostly function

>>925295
Pro tip: If you get the solder on ones plug them in a socket wile you are soldering and be quick. The pins can move with the heat.

>>925296
It may have leaky capacitors. Its a real basic unit this one.

R1 and R2 will be input level. R33 and R38 should be X / Y position. Being AC coupled it will only be good for AC signals like audio etc. I can't read the Russian but the rest is mostly the same symbols to western schematics.

>>925277
This excellent video suggests that it might be a capacitor with high ESR https://www.youtube.com/watch?v=qmnTKoNwJdk

>>925300
Yeah it just the most basic of the basic units. 80kHz max range. I'm fixing it up out of nostalgia and general sex-appeal.
Think i might make a little tennis for two simulation for a collage presentation or something.
The Russian just lists the diodes and tubes (equivalents) used in the circuit.
I might swap out the capacitors after all the unit was made in 75 so the caps are at lest 40 years old. so it's safe to assume that everything is busted.
I noticed that the beam shifts slowly to the left as the unit warms up. So I'm thinking dried up capacitors or tube capacitance gone wild . I haven't opened it up just yet but it's likely to have wax paper capacitors inside it.

>>925303
>nostalgia and general sex-appeal

If that is the case you may want to do nothing. I have seen some Soviet export electronics and the components are unique. Changing them would be.....
>This kills the Soviet sex appeal

>wax paper capacitors
Those were often an issue.

>haven't opened it up just yet

Post pics when you do.

File: Untitled-1 copy.jpg (32KB, 329x135px) Image search: [Google]

32KB, 329x135px

Is this sufficient to make a start?

I have some components and a breadboard

File: 2016-01-05 13.01.10.jpg (1MB, 2560x1920px) Image search: [Google]

1MB, 2560x1920px

>>925296
Ok found the fault. Tubes
The tube was overworked at some point and flaked, replaced it with this sexy new thing now it works like a charm.

File: et_tip.gif (38KB, 722x914px) Image search: [Google]

38KB, 722x914px

I bought a WESD51 soldering station during Christmas sales. What tip should I get? I mostly solder protoboards with through-hole components.

>>925368

you need a minimum of 2 tips: screwdriver and conical. if you can only have 1, then i'd go for conical coz it can emulate the ability of the screwdriver tip to provide greater thermal capacity. you do that by using the side of the side of the tip, about 1/10-inch back of the tip.

there's no way to emulate the fine tip of the conical using a screwdriver tip.

i want to have a start up sound when i turn on my car (think like windows startup but different) and im strugling on what parts i need. i need something like an mp3 player that has some memory for a soundfile on 12v (or could be made working for 12v) and something like a timer deactivated relay. but as far as i can find it does not exist.

>>925397
Dose your car have a stereo?

>>925407
car has a radio

>>925408
Set it up so it tuns on when the car tuns on. Store the sound on a usb or something and have it play it when it turns on. If your radio can't play CD-s usb-s or medai cards, you ca buy one of those cigar lighter things you can stick if your lighter slot or run wires to. alternatively you can use a raspberry. they can FM transmit over a very limited area, or you can just nigger it in to the stereo with cables.

>>925049
That's the exact kind of waveform I was getting. I figured it was probably the slope. But that wave doesn't seem like it would be a harmonic "subset" of a square wave anyway. Looks like even harmonics have been added or something. So how, then, is an RC "filter" even a filter?

Also, the harmonic content of a square wave already is 1/f - I'd have thought that a low slope filter would maybe reduce it down to a triangle wave, where each harmonic is 1/(f^2).

This seems to be playing with the harmonics in a way that I would not expect a filter to.

>>925055
Just wanted to make a sine oscillator to experiment with transistors with. I might just forget it though, as every attempt to do something even vaguely practical in this area ends with the laws of physics changing just to spite me. You know, "filters" suddenly adding harmonics and changing waveshapes in strange ways.

Meh.

File: Cauer_Topology_Lowpass_Filter.gif (14KB, 634x225px) Image search: [Google]

14KB, 634x225px

>>925460

filters are more complicated than you think. you cant just put a bunch of low-pass filters in series and expect them to add. there's a lot of complicated math behind the component choices, thanks to people like Butterworth and Chebyshev.

>>925268
>banggood
Thanks for that site, they seem to have some rather nice Famiclones.

>>925511
So you'll never see an RC filter in an amp, synthesiser, etc? Why do they even teach them then? They seem utterly useless in the real world to me.

So does this waveform now have even harmonics? I thought that any wave where each half was vertically symmetrical was a sign of only odd harmonics.

How can it even be called a filter if it adds frequencies that weren't there?

>>925539
> Why do they even teach them then?

it's tradition: they learned it so now you have to. same with equally useless stuff like finding the are of a rhombus, or hyperbolic functions.

>>924861
I did this, after. I got a 10A transistor that I salvaged from a PC power supply.

I hooked up the a 555 to a 4.5v power supply and the speaker to 15v on a different supply (shared ground).

Then I ran a 10k pot and 1k resistor from the 555's out to the base, then connected the speaker between 15v and the collector, then emitter to ground (it's NPN).

What happens is that the speaker's voltage has no effect on the volume after about 4v. It just stops getting louder.

The pot on the base has an effect on the volume, but only as far as the speaker's supply allows.

If I up the voltage to the 555, though, then the speaker gets louder. I drove the 555 with 12v in the end. It was louder, but the speaker's supply voltage didn't have any effect.

Also when I looked at the speaker on the oscilloscope, the (square) wave had been high pass filtered. You know, like when you put a cap in series and it just becomes alternating spikes.

What's going on?

Also, is it time for a new thread yet?

>>925539
Wait so what kind of filters do they use

>>925545
Alternatively, can someone just explain how you use a transistor to, you know, make a signal louder?

It's just so ludicrously convoluted isn't it? Common base, common emitter, current gain, voltage gain.

I just wanna make something louder. Aren't all audio things in terms of volts anyway? Like line out is peaking at some voltage like 1.8v (or whatever it is), then I want to turn it into a signal that peaks at 30v or whatever the speaker wants.

Why do I even care about current? How are voltage and current gain different? Doesn't one rise proportionally to the other? Like if I put 2v into a 100 ohm resistor, I get 20mA. If I change it to 4v then I get 40mA, etc.

I just don't get the distinction or anything. Nowhere explains it either.

Why all the fucking maths? I just wanna take a 5v signal and make it into a 15v one (or whatever voltage the thing I plug into it needs).

Why confuse people with all these different configurations when all they're supposed to do is make something louder?

If i'm using a transistor to modulate between open and short circuit on the collector and emitter path, then it should just go between my supply voltage (when the transistor is open and the speaker has a voltage drop) and 0v (when the transistor is closed and both ends of the speaker are at positive).

Isn't that basically it? If not, why not? Can't anyone invent something that makes it work logically?

Can anyone point me towards something that explains them properly and takes you through the process, rather than casually dropping in terms like "current gain" and assuming you've done an engineering degree?

How. Do. I. Use. A. Transistor. To. Make. Something. Louder? That's literally all I want to know. All I've ever wanted to know, but apparently it's too much to ask.

>>925571
>(when the transistor is open and the speaker has a voltage drop) and 0v (when the transistor is closed and both ends of the speaker are at positive).
Other way round but yeah

>>925567
Chekovsgun Popinofftodashops ones probably.

>>925575
:^)

>>925571
Mother fucker chill. How about you go get a god damn book and figure it out? Also get over your aversion to math. Transistors are highly mathematical in order to get them into the proper operation mode.

http://blog.oscarliang.net/bjt-bipolar-junction-transistor-beginner-tutorial/

See, this is the kind of thing I'm talking about! Introduces it with a fairly understandable graph and explaining about how to use as a switch.

Then onto the brilliantly comprehensive and useful bit on amplification:

>As an amplifier

>When used as an amplifier, the biasing is arranged so that the transistor operates in the linear region ( shown above as almost horizontal sections). An amplifier will usually be biased to about half the supply voltage to allow for maximum output swing.

That's it! No explanation of biasing, the idea behind it, examples, etc. Plus, isn't a transistor (famously) a current sensitive device? Where does voltage come into it? And how do I perform this operation?

This is the kind of stumbling block I always encounter on these things. They just casually drop in terms like that, assuming you know.

>>925593
I'm not averse to maths, as such, but my concept of transistors is riddled with holes and inconsistencies because of the way these borderline-autistic engineer types think is a good way of explaining things.

Why does nobody seem capable of giving a simple ground-up explanation? Not an encyclopaedia, but a few paragraphs and pictures on literally every single principle at play, in some logical order. I want to establish all these little quirks and tenets, to allow everything else to follow logically, but these people just won't let it happen.

Every one of these sites I look at leaves me with these niggling little questions that my brain won't let me proceed until I'm satisfied I understand what's happening.

>>925597
Oh, and pretty much every YouTube video I watch comes up with some text halfway through saying "OOPS MY BAD I DONE A MISTAKE THERE I MENT TO SAY X NOT Y OH DEARIE ME". As soon as I see that I switch off. I'm not listening to someone who can't even explain it themselves without retro-annotating.

File: success.jpg (26KB, 462x480px) Image search: [Google]

26KB, 462x480px

>>925571
It's convoluted because physics is convoluted.

Unfortunately, for the time being, electronic components must be made from real materials which will neccessarily make them imperfect, introduce parasitic properties, nonlinearities, side effects and all kinds of nasty shit.
I completely feel your frustration though. Transistors, as simple as they might seem at first, are pretty damn complex. Maybe this will help a bit?
https://learn.sparkfun.com/tutorials/transistors

Anyways, consider using an op-amp instead. Those are (sort-of) easier to understand in simple circuits and have more ideal properties. Of course they also have their own limitations that you'll need to be aware of.

tl;dr EE is hard, that's why it's so rewarding and why you are here

>>925600
>Anyways, consider using an op-amp instead. Those are (sort-of) easier to understand in simple circuits and have more ideal properties. Of course they also have their own limitations that you'll need to be aware of.

That's true enough. Everything I read about them makes total sense. Especially the idea of using negative feedback to control gain with just a resistor. Haven't done much with them yet because I naturally assumed they'd be more complex than transistors (to use at least).

File: tronsostor.jpg (86KB, 484x920px) Image search: [Google]

86KB, 484x920px

See this pic here. Is this right? There's a base voltage/current/whatever that makes the transistor a short circuit - effectively a wire. The full voltage supply is available.

Then there's zero voltamps at the base which makes the transistor close up completely. As if the wire was pulled out.

So, between those two levels (zero and whatever the one that makes the transistor open up completely), there must be a continuum that allows any and every degree of open-ness, which is what allows the whole range of voltages on the output?

I doubt that's right, so can someone just tell me why? For one thing, I can't see how the intermediate degrees of resistance between fully open and fully closed change the voltage.

I mean, whether I put a 10 ohm or 1 megaohm across a supply, it's still gonna be dropping 10v right?

This is the kind of thing I'm talking about. It just doesn't add up in my head at all.

>>925612
And another thing: when it says X collector current, does that mean the maximum current if you shorted it?

Because, surely the impedance of the load would change that, no? Like if I do the maths and it says "this base current gives that collector current", then if I splice an 8 ohm speaker in there then it's not going to have the same current as if I put a 4 ohm one, is it? Or is it? I just don't know because nobody thinks to explain these things in their little articles.

Which brings me to another thing. How do you use ohm's law to find out how a current changes with resistance?

You can derive a voltage from a current, a current from a voltage, but how do I take a starting current, apply a resistance (in a formula) and get the resultant current out?

There's never been any kind of explanation there. Concern seems to arbitrarily switch between volts and current.

You start with a voltage, apply a resistance and get a current. So now what? We can forget voltage? No, because at some point, voltage randomly comes back into play with no explanation.

>>925612
>I doubt that's right, so can someone just tell me why? For one thing, I can't see how the intermediate degrees of resistance between fully open and fully closed change the voltage.
>I mean, whether I put a 10 ohm or 1 megaohm across a supply, it's still gonna be dropping 10v right?

Or does the transistor become a voltage divider in combination with the speaker's own impedance?

File: mode-quadrants.png (53KB, 903x885px) Image search: [Google]

53KB, 903x885px

>>925600
>https://learn.sparkfun.com/tutorials/transistors
Like see how this is all about voltages. I thought it was a current sensitive device, so why are we talking about voltages again?

I thought it was "more current at base allows more current through the other 2", what's all this about voltage?

Literally how do I just quite literally do something as trivial as literally making a 1v signal modulate another voltage source, so I get a, say, 20v signal?

How does one come up with the solution when someone says "this is a crappy signal that peaks at 10mV and I want to scale it up so that it peaks at 20v to drive this big fuckoff speaker"?