Do you have a stupid question about LEDs?
are you building a vape and want to know what electricity is?
Did your mom buy you a stolen arduino for Christmas with food stamps?
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?
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.
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?
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.
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...
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.
Anyone who says they have is lying
Just go be an electrician if you like circuits and instrumentation
tell me more about how i dont do what i do, friend
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.
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.
(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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
>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.
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.
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.
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.
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.
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.
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?
Which thingy do I set it to to test that
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
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.
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.
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?
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.
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.
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.
> 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).
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.
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.
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.
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.
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.
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...
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.
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.
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.
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.
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?
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
This is the buzzer. It's a Velleman SVM06 SOLID-STATE BUZZER.
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.
>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.
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.
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.
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.
I wouldn't have thought so. Unless you mean loosely based on the same principle.
>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?
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.
>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.
>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.
>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.
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.
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?
>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.
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.
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).
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.
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?
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.
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).
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.
Shit wrong image, this is the right one.
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.
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.
This particular one is 1 farad but only 2.5 volts.
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.
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.
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.
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?
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?
>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.
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?
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
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?
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.
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.
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.
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
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?
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.
>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...)
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?
>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...
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.
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?
>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.
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?
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?
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.
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?
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.
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.
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.
Get back in there and do something to do with capacitaters.
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
It's not the exact model, but it's the closest I could find.
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:
>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.
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?
This is from a Philips inverter (SEM SIC-130T) designed to go with that display's lamp.
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.
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.
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.
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
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).
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.
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.
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.
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.
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.
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.
>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?
>Bought a cheap-o bench power supply
>Plug it in
>Not plugged into anything else
>5min later it just dies
Did I get a dud or what?
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.
>did I get a dud?
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?
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.
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.
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.
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.
I've been jacking off to it for a few days now. will dump picks
Original packaging with Moscow (loosely translated) radio electronics administration stamps.
Even has a passport
After some niggering about got it to mostly function
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.
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.
>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.
Is this sufficient to make a start?
I have some components and a breadboard
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.
I bought a WESD51 soldering station during Christmas sales. What tip should I get? I mostly solder protoboards with through-hole components.
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.
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.
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.
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.
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.
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?
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?
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.
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.
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.
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.
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.
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?
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
>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).
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.
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.
>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?
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"?
Hi /ohm/, I bought a N070ICG-LD1 screen for use in a DIY VR headset
The screen took ages to arrive so I don't really want to send it back but I think I killed it
I'll greentext my history with it
>it arrives with all but screen plugged in
>has three AV things sticking out except the red one looks like it wants power so I unplug the 3 AV looking cables from the board, this probably isn't important
>plug the screen in
>didn't come with a power supply but I had a 12V 1.5A one lying around and the eBay page said 12V so I gave that a whirl
>works a treat
>watch some test videos on it
>unplug it all as it's getting a bit hot
>fuck around a bit
>plug it back in and it's all blue and shit
>when I touch the screen the colours just get weirder
>unplug the screen and plug it back in
>tiny amounts of fucked colours
>unplug and plug back in about 3 or so times
>all I get is black
What do? Any pointers?
and the power adapter
Is it possible that I just need to give it more amps?
I think you're right
I've wiggled the shit out of it
It might have been wiggling that got me here in the first place
Well anyway I've contacted the seller and requested another cable, hopefully that solves the problem
Thanks for the suggestion though
So what's the thing with voltage drop then? I see the idea but it's not pinned down fully. Like, if I have a 5v source and put a 100k resistor across it, one side shows 5v, the other shows ground.
If I change the resistor to... anything really, 1k, 1M, 220, etc, then it's the same drop isn't it?
All the voltage on one side, none on the other.
But then if you put a wire across it (short circuit), then the voltage drop goes away.
So is there a small region of low resistance where the voltage drop varies continuously?
I made an experiment to figure that out. I put 4 10ohm resistors in parallel to make a 2.5 ohm (but both multimeters showed it to be in the region of 7.5-10, don't know what's up there), then a 10k pot in series.
As I lowered the resistance of the pot, the voltage across it stayed constant for a long time. Then towards the end it suddenly dipped.
I turned it back the other way but it didn't move back. I managed to nudge it back to the true voltage reading but there seemed to be some hysteresis.
I tried it again and found that I could get the measured voltage drop to roughly half (regardless of supply voltage), when the pot was in the last few degrees of travel.
I kept trying to find the "bite point" (so I could switch it off and measure the actual resistance. But I kept overshooting and finding myself in hysteresis.
Then I saw sparks coming out of the pot and it smelled so I stopped.
But I was onto something. There seems to be a small region where the all-or-nothing principle of voltage drop was invalid - I could vary it but it was very sensitive and, as I say, I could never find the exact point the drop began to tail off.
It seems like 0 ohms = no drop, then you put any resistance and suddenly the voltage drop matches the supply, no matter the resistance value. Yet there's a small region where it's proportional.
Is there any explanation for this? Is there some formula to work out how to get, say, a voltage drop of half the supply voltage?
I'm not talking about voltage dividers, I'm talking about how there seems to be a point from <10 ohms to infinity ohms where the voltage drop is constant, then somewhere below there's a region of continuity. I think you missed the point entirely.
I've never heard this explained. And I don't like "holes" in explanations. Stops me from proceeding.
At what resistance does the voltage drop go from 0 (as in a short circuit), then begin to rapidly jump (converge on?) the full supply voltage drop
Your experiment was literally a voltage divider with a supposedly 2.5ohm resistor and a ~1-10k ohm resistor. When the pot was at the same resistance as the other resistor, you got half voltage.
I notice that nobody seems able to answer my question about the lowest resistance that gives (near as dammit) full voltage drop.
It's somewhere between 0 and 10 ohms. 0 ohms = 0 voltage drop, 10 ohms = full voltage drop... but somewhere inbetween it varies continuously.
I imagine the graph would look something like this but I never got to fully document it.
There's a link and an Open button that both point to the same URL. This is what I get from it.
>I gave permission to your Hotmail account.
I thought you just gave me a private link that didn't need a login. Like you can do with Dropbox.
Are you saying you gave me a link intended to be used through MSN or something?
Are you measuring Vac or Vbc? Power supply or battery? What's the lowest resistance of your pot?
The fact that you were unable to get 2.5 ohms from connecting 4 10ohms in parallel makes me question your experimental abilities.
>The fact that you were unable to get 2.5 ohms from connecting 4 10ohms in parallel makes me question your experimental abilities.
AC obviously. I was testing voltage drop you patronising fucking idiot. I just put the 2.5 ohms in so as to have a small "buffer" against a complete short circuit. I was using a 10 ohm at first but it was too high in resistance.
I was simply testing *a* resistance, the fact that I composed it out of sub-elements in a complete red herring.
I wanted to measure the complete drop over *a* resistance (however constructed) to find the resistance value where the potential difference between + and ground began to move towards 0 (towards a short circuit, but not quite attaining it, if you will).
It's like you didn't even read my post.
And as for the 2.5 ohm thing? What do you fucking want me to say? I put 4 10 ohms in parallel and it read about 7 on the meter. That's literally what transpired.
I ended up buying ten micro usb connectors for $.88 because I only needed one to repair a cable and it was actually cheaper to buy 10 than just 1. I have an old western digital hard drive that works just fine but the usb connector is recessed and most cables have too thick of a plug or the connector is not long enough. My custom connector fit perfectly though.
Anyway, I would like to use some of my extras to make some custom usb cables. Does anyone have any suggestions as to where I can acquire some usb cable without buying premade cables? I'm looking to make some longer cables like in the 10' range and some shorter cables that are only a few inches. I also need to pick up some usb plugs so I'm leaning towards getting extension cables and just hacking off the female end for the long ones but that seems like a waste for the short ones.
Initially I was going to use some cat5 but after reviewing the specifications for usb 2.0, I realized that cat5 would not work, as it does not have appropriate shielding. I googled it but most people end up replacing the connectors on premade cables but I would just like the wire itself. Any ideas?
Then the case is likely that your power supply is hitting the current limit and the SCP circuit is engaged. The current falloff looks like a rounded rectangle because of transistor saturation and such, which is how you got the half voltage. This is a hardware limitation and not a hole in theory because in life, there do not exist ideal power sources.
Hello transient beings of /ohm/,
So I blew out the charging base of my Baofeng HAM radio with 12 volts, when it needed 10 volts.
I already bought a new one a while back, but I'm wondering if I could fix the old one with a new lithium charging board.
The battery pack is 8.4v, so I went to eBay and searched for a 2 series lithium charging board. All I could find however are these boards that have a balancing pad that goes between the 2 cells. The battery nor the base have a 3rd terminal, so it's just a postive and a negative going in.
Could I still use that board to safely charge the battery? It also doesn't have an indicator light when it's full so that's also something I'm worrying about. ( I could just calculate the approximate charging time but I'm not too fond of that method)
My new charger base also stops charging when it's 8.2 volts instead of 8.4, which pisses me off a bit since I'm not getting a 100% charge. Could I fix this as well? I don't want to buy a new one *again* just because this one is kinda DOA. I still use it though, and I should have noticed it earlier and disputed it with the seller back then. Don't want to do a paypal claim because I think that's a bit unethical.
Pic related of the charging board and info. What would be the correct input voltage for that board?
Maybe but that still doesn't answer the continuum that MUST exist between 0 ohms (voltage drop 0) and the lowest resistance that reports the full supply voltage drop.
Why is nobody getting what I'm saying?
Anyway last night in bed I pondered (like I do) and remembered reading about current shunt resistors.
Very low resistance that barely alters the current but reports a small voltage drop that can be translated into a current reading.
So there's another piece to the puzzle. I'm amazed that I seem to be the only one who thought of that.
It's like nobody here can even comprehend what I'm trying to enqire about.
i learned "normal" and reflow soldering during an internship last year. took me a couple of days of practice, it really isn't that hard. i even felt good enough to make an educational video about it.
check it out:
Then how come the voltage drop across a resistor in parallel with the supply is always the supply voltage no matter if the resistance is 100 ohms or 15 googolplex megaohms?
Except that bit right at the beginning. The bit I'm talking about.
It's clearly not linear, whereas that formula clearly is.
Because that's how a DC power supply works. It supplies a fixed voltage and however many amps the circuit will draw.
The 0 volt dropoff you're measuring is not a short circuit voltage. It's the power supply turning off because it cannot supply enough current to satisfy ohms law. It's also to protect you from doing stupid things like making your pots smoke because many components are not rated for high current.
Are you saying I'd get different results with a battery?
Anyway I never made a true short circuit. And this power supply can supply 3A. Of course 0 ohms is infinite current but in the range I was operating in it should have drawn half that. Assuming that the resistance was ~7ohms like the meter said and not 2.5 like the maths said. Who knows, maybe one (of the 4 10 ohm parallel) of them was duff.
I admit I wasn't watching the current meter on the supply though.
But voltage drop is inversely proportional to current in the resistor, right? So the maths does say that a short circuit (ie a resistance of about <2 ohms or whatever it would be in practice) should show a voltage drop of 0 as the current through it would be very high (not infinite like an ideal short circuit).
But I've heard it said that "every branch in a circuit must drop the full amount" or words to that effect. So a voltage source "shorted" by a resistor will show full voltage at one end and 0 at the other yes?
And if it must always drop the full amount, then that resistance wouldn't matter. It all has to go somewhere right? And doesn't that bear out? I did it with a 1k and a 100k and got the same voltage drop. Why should it change?
So it's constant from somewhere under 10 ohms up to infinite ohms. Yet before that, it's continuous.
And then the current shunt resistor also suggests that. For obvious reasons it's barely even a resistor - and consequently its voltage drop is in the mVs.
So when you're in that region, there's a continuum but when you're out of it, then it's a constant, flatline. As in, it appears that a 1M resistor would have to drop the full voltage, same as a 1k.
>Are you saying I'd get different results with a battery?
sort of, because it doesn't have SCP but it does have nominal internal resistance which will limit its current output. It'll get really hot really quick and burn out pretty quickly though.
>I admit I wasn't watching the current meter on the supply though.
You should be pulling 5/7 amps at 7 ohms or 1.5 amps at 2.5 ohms. If your power supply is shutting off before then, something is wrong on your end, not the theory, not because of any "holes".
>But voltage drop is inversely proportional to current in the resistor, right? So the maths does say that a short circuit (ie a resistance of about <2 ohms or whatever it would be in practice) should show a voltage drop of 0 as the current through it would be very high (not infinite like an ideal short circuit).
A true short circuit is in the range of milliOhms and much less. So even at a few amps, the voltage drop is negligible.
>"every branch in a circuit must drop the full amount"
If you don't get this, you serious need to review Ohms law and kirchoffs laws. There is a fundamental misunderstanding of this stuff on your end which is mucking things up.
>And if it must always drop the full amount, then that resistance wouldn't matter. It all has to go somewhere right? And doesn't that bear out? I did it with a 1k and a 100k and got the same voltage drop.
>Why should it change?
>So it's constant from somewhere under 10 ohms up to infinite ohms. Yet before that, it's continuous.
>As in, it appears that a 1M resistor would have to drop the full voltage, same as a 1k.
I don't know what you're not understanding.
Well this is what my arduino is doing at the moment
I did 50 leds on a 60" TV and it looks great. Buy the led strings on ebay and make sure they have the right chips in them.
Incidentally, last night I stumbled on some youtube videos about batteries, internal resistance and terminal voltage. It was quite enlightening. I think it explains my question quite well. I see now how the PSU was compensating for that.
>>So it's constant from somewhere under 10 ohms up to infinite ohms. Yet before that, it's continuous.
>>As in, it appears that a 1M resistor would have to drop the full voltage, same as a 1k.
You've contradicted yourself there though. 1M drops the same as 1k drops the. You said it yourself. Just before that you denied it was constant at any point.
People like you are responsible for this "fundamental misunderstanding". I mean, look at how long it took you retards just to get what the fuck I was even asking. I didn't want to post loads of massive posts but it seemed like I had to.
>A true short circuit is in the range of milliOhms and much less. So even at a few amps, the voltage drop is negligible.
Right, so by your own words, 0 ohms drops zero, 1k drops 5v, 10k drops 5v, 100k drops 5v, 1M drops 5v. The bit I'm fucking talking about is the bit between zero and the LOWEST RESISTANCE THAT REPORTS A FULL VOLTAGE DROP.
I'm sure you're very good at what you do but, FFS, don't ever consider a career in teaching.
How can I hook up one button to toggle between switches?
Basically I have two LED's one white and one blue. I want to have one LED on when the switch is not pressed, and then when the switch is pressed i want it to turn it off and then turn on the other LED.
What is the simplest way to do it? I only have resistors and a few diodes.
Ideal 5V voltage source:
R > 0: voltage drop = 5V, I = 5/R
R = 0: voltage drop = 0V, I = infinity
There is no continuous region.
5V voltage source rated for 6A, current limit set at 5A, SCP engages at 5A:
R > 1: voltage drop = 5V, I = 5/R
R <= 1: voltage drop = 0V, I = 0A
The power supply shuts off at a load of 1 ohm or less. This shutting off is not instantaneous and is based off the graph I posted earlier. That is the continuous region you are seeing and it is due to the transistors in the SCP circuit. The continuous part begins once the SCP circuit engages.
>Ideal 5V voltage source:
>R > 0: voltage drop = 5V, I = 5/R
>R = 0: voltage drop = 0V, I = infinity
>There is no continuous region.
Bullshit. That's impossible. So: R=0: 0 drop, R=0.0000000000001: full drop? Then how do current-sensing shunt resistors do their thing?
Sorry but this is the source of my whole confusion. You don't need to know about electronics to see that this cannot be true. We live in an analogue, continuous world (at least as far as us macroscopic beings are concerned).
>Ideal 5V voltage source:
ie it doesn't exist in real life but that's exactly how it'd work if we could have infinite current.
We live in a continuous world, but think about this. I can almost close a door so that there is an infinitely small gap, it's still open. Nudge it once more and suddenly it's closed. Some things are discrete mang.