/ohm/ - Electronics General

>>933576
http://pastebin.com/9UgLjyND

Pastebin link that was supposed to be in the OP because I'm a retard.

>>933576
I don't see any benefits of AVR against ARM

In the long term, it is better to have more ARM experience than AVR experience

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>>933626

That can be said of any 8 bit MCU architecture

Also

I just programmed a led blink program into a PIC16F628A. What do I need to know before I design and build a development board to house it? I'm not a complete noob as I've made dozens of boards before but it's my first time with a PIC, basically.

>>933626
AVR is still better than PIC. And ARM is better than the MIPS cores Microchip puts in their PIC32.

Microchip's architecture made sense in the '80s and '90s, when they were manufactured on huge 1200nm processes, and people weren't concerned about power consumption. Today, microcontrollers are typically manufactured on 180nm processes. The die size is dictated by the number of I/O pads, leaving room for enough transistors for a much more capable core than Microchip's legacy garbage.

Let's hope Atmel's cores infiltrate PIC, and not the other way around.

>>933637
It's been ages since I used those, but IIRC there weren't that many gotchas. The timer 0 input is limited to open collector only when used as an output (so you might want to add a pull-up resistor) and if you insist on using the reset pin as an input, you need a diode or something when using high voltage ICSP. And of course you need to prevent the external stuff from fucking with the other ICSP pins during programming.

I think Intel announced that 8b processors were a dead end in the last millennium. They were trying to push their 16b 80196. Which is now dead.

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I have to solder a white 3mm led and I was wondering if I can recycle one of these 75 ohm resistance, since I need one.

>>933686
Sure. It would probably be easier to use through hole though, SMD isn't particularly friendly unless you have a masked PCB.

>>933686
it's no problem. easier if you have 2 pencil irons to harvest.

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>>933699
I don't think it's masked.
And the holes are pre-filled with solder.

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Can anyone help me with why this circuit doesn't work? I'm running some example code that just blinks the LED when a key is pressed.

>>933745
MIDI in, that is.

>>933745
the led isn't blinking because it isn't there.

>>933750
Sorry. It's the built-in LED connected to pin 13 of the Arduino.

>>933751
well if its example code then it should be ok but check the pin assignments.

your + and - in >>933745 are connected to the arduino right? like specifically the ground is connected to the 0v of the arduino?

i guess check the midi connector pins are right and you haven't mirrored them or something.

this is where a scope comes in real handy.

>>933754
>like specifically the ground is connected to the 0v of the arduino?
>i guess check the midi connector pins are right and you haven't mirrored them or something.
Yeah both 5V and GND come from the Arduino. I've tried the pin wires both ways around. When I put them the other way, temporarily, the RX light would light faintly and then flicker if I pressed a key.

So I guess that would be the wrong way. I think I have it the right way.

This has been such a fucking saga though. I've been trying for ages to get this simple connection. Before, it turned out I ordered the wrong opto-isolators so it didn't work. Every time I think I've got it right, some other bullshit rears its head.

>>933754
>>933756
And why is there even 1 base pin, let alone 2? I thought the internal LED lighting up was the "base".

What's that all about?

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>>933576
This is suppose to take a non obd2 car computer and get the codes off of it by connecting to the serial on a computer.
What does /ohm/ think?
Does it look safe to use?
Does anyone see anywhere that couple be improved?

>>933759
you bias the base to increase the sensitivity so the led has to light up less to turn the transistor on.
the rx light is connected to what exactly? its the led you are trying to light up?
sounds about right
midi will send data when the key is pressed and again when its released i think, the light won't stay on the whole time the key is down.
you need to check that though.

>>933766
The RX light is on the Arduino board. I'm no stranger to MIDI. I've successfully got an Arduino to send MIDI out to my piano. Just can't get the reverse to work.

This code is meant to light up the LED on pin 13 - but the RX light is hardwired to light whenever something is received. I have not yet achieved this.

wut soldering iron is gud?

Due to my general ignorance as a teenager, my soldering iron's tip has decayed into a giant mess that is nearly impossible to do anything precise with. I can't find a replacement tip that fits, so I'm going to get a new one. Variable temperature would be nice, a wide selection of well-labeled replacement tips would be nicer. Budget of $50.

My expensive but cheap maplin (Kinda like radioshack) soldering iron died on me.
I need a replacment for the odd soldering job. I've seen some of the re-work station sets for around £50-60 on ebay and I was wondering if they are any good for the budget concious hobbyist?

http://www.ebay.co.uk/itm/2in1-SMD-Hot-Air-Gun-Rework-Soldering-Iron-Station-Lead-Free-Welder-4-Nozzles-/310770402991?hash=item485b5c06af:g:HMMAAOSw0HVWCf77

http://www.ebay.co.uk/itm/New-2in1-Soldering-Iron-Rework-Station-Hot-Air-Gun-Solder-Welder-Digital-Display/310770370634?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3Dc637de21ed39421aa88f019351e5880b%26pid%3D100005%26rk%3D1%26rkt%3D6%26mehot%3Dpp%26sd%3D310770402991

Also would this flux be ok to buy? What one is best the No clean or the standard flux? I do a tiny bit of board repair and mostly wire soldering.

http://www.ebay.co.uk/itm/Liquid-Flux-No-Clean-or-RMA-rework-reflow-pcb-repairs-50ml-brush-applicator/111832268566?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3Df7d3fd6ec4bb464ba8336422c5b96999%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D121054733532

Finally I cant budget for a fluke MM so would this do ok?

http://www.ebay.co.uk/itm/321362994449

Mainly basic tasks, im no ee expert so advanced features and precise readings aren't too important.

>>933779

You need to use them to know which one is better, but standard flux will cause copper to turn green really quick if it's not cleaned with isopropyl alcohol

>>933800
Are the no-clean fluxes generally good though? Or are they one of those things you shouldn't really use?

>>933769
Okay it turns out I did have the MIDI pins the wrong way around. I found another schematic of the same thing which was more clear: the pins are as you're looking at the plug. The other one just said front view, which I assumed to mean of the socket.

That was with some example code that uses the software serial library. That was the code I was using when I got it to work. I was also trying out some code from another site, which used the standard serial interface.

That was the one where I tried the pins both ways around and one way made the TX light light up faintly (which I presumed to be the sign of error). However, in my earlier post I said it was the RX light, which would have made more sense, surely?

Then I realised that in that code, the function that blinks the LED on pin 13 wasn't even being called.

I changed that, now that example works too. But still, the TX light remains on very dimly. No idea why but it's working now.

So that's that I suppose.

>>933801
They're better, but still need to be cleaned

>>933800
>but standard flux will cause copper to turn green really quick if it's not cleaned with isopropyl alcohol
That isn't the case with the rosin in the solder's core too, is it?

>>933811
Thanks. I'll give it a shot.

Any ideas about the iron and multimeter though?

>>933812

You can leave it if the circuit won't get too warm. When it's in liquid form it becomes corrosive, but I've never actually seen the bron/black stuff corroding any of my boards, so I've never bothered cleaning it.

>>933815
I didn't know that. Luckily I know someone who has a big bottle of alcohol.

>>933813

The cheap chinese copies of older designs will definitely work for hobby use, but they're not really well made.

The good soldering/rework stations are made by companies like Hakko and Weller, they're much more expensive (cost 10 times more) and are supposed to last much longer.

Would it be feasible to build a DIY UPS?
* Bypass circuitry using relays
* Rectifier
* Battery charger
* Inverter
* Grid sync
* Current and voltage monitors

Possibly some power factor correction circuitry.
Controlled by a RasPi with a web interface and custom SNMP server, and some AVRs for more specific tasks.

>>933996
Of course, but you better 100% know what you're doing cuz muh wall voltage.

> Would it be feasible to build a DIY UPS?

who needs a micro-controlled web-interfaced UPS? the same kind of twit who needs a nuclear powered coffee mug. it's silly to recreate solutions to problems when cheap commodity items already exist to solve those problems, while millions of other cool problems remain unsolved.

also, you can find used UPSes cheap. replace the battery and they're good for another decade. and, the bypass function is done with thyristors, not relays, coz they're too slow.

>>934012
>who needs a micro-controlled web-interfaced UPS?
Anyone who wants their server to sync its disks and switch off before the power runs out?

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>>934036

for any kind of critical functionality, you'd get an enterprise UPS system, and not rely on some botched together beta-quality Linux OS running amateur-level Python scripts with zero quality control testing.

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To drive a small DC motor (like the one in pic related) via PWM, would I need to get a motor driver IC or would something with an op amp work? what advantages would there be to using a driver?

>>934051
Driver ICs with PWM and H bridge are very convenient.

>>934054
>H bridge
I just remembered that's what I used last time I did this, so I will use that instead of my op amp idea (which I don't think would have worked anyways due to low current output).

>>934047
You act like NUT isn't a thing.

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>>934057
H-bridges and PWM controllers are two different things.

H-bridges allow you to invert the polarity of the voltage supply to the DC motor, thus reversing its direction. If you only need to run your motor in one direction, you don't need an H-bridge

PWM controllers allow the DC voltage to be 'chipped' thus allow you to control the speed of the motor in either direction. If you don't want to control the speed of your motor (ie. run it at the fastest speed possible) then you don't need a PWM controller.

They are commonly used together like pic related to control both the direction of the motor and the speed of the motor.

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Separate general for arduino/microprocessors when


You software fags need to leave

>>934083
But everything is software, anon.

Whether it's expressed as components or C is an implementation detail.

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>>933576
>mfw having a lot of old microcontrollers

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>>933686
what kind of resistor network is there??

fuck you and your safety.
https://www.youtube.com/watch?v=3ugxq0FMjoQ&index=20&list=PLTVpTfT-O9UeboWth9LTrdclUzaO2LvfT

>>934116
It's probably pull up or pull down for the pins.

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Hello /ohm/

Are there any BJTs that can be run directly from digital circuitry (saturation at base current = ~20mA at ~12 volts) and can pass ~6 amps between the collector-emitter?

This needs to be available in both NPN and PNP construction (this is for a motor H-bridge).

I can't find any transistors that fit this specification. halp?

>>934198
Use FETs, broski

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>>934198

teaching a man to fish: electronics retailers have charts where you select the parameters you want and it tells you what's available. like this one: http://ca.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/Darlington-Transistors/_/N-ax1sb/

after selecting some parameters, as per the pic, it lists 4 devices that fit. then you look at each datasheet and see if it'll work. i was gonna suggest the MJE5740 and MJE5742 but their gain is pretty shitty (typically 400) so they need about 200mA gate drive, which is too much for your needs.

>>933686

Yes but those are so cheap, take them if you're in a hurry

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I ordered some ICs on amazon because I had gotten a gift card for christmas. The dipshits literally just ordered the shit from mouser and had it sent to me, but charged me twice as much. That alone wouldn't annoy me as much as the fact that they only sent one of the four items I paid for. Making a business simply out of filling in orders at other websites but selling through amazon is kind of a good idea, but how do you fuck up such a simple job?

>>934198
use a FET, or use a darlington / compound pair if you're dead set on BJTs for some reason.

>>934273
Do you not shop around for the best prices first?

>>934311
I shopped for the places that had everything I wanted so I didn't have to pay twice for shipping, and I shopped for somewhere that wasn't china so I wouldn't have to wait 2 weeks to get re-labeled ICs with broken pins. I had to shop on amazon, as I said before, because I had an amazon gift card. Normally I'd just order directly from mouser or digikey.

I need to chose a platform for a simple robot, A small ARM board is easiest to program, but I need real time with safety features. Is there a way to make generic arm boards safe? Or does the bootloader stop them from rebooting in milliseconds if theres a fault?

Any other suggestions for safety platforms? I looked at the TI hercules with lockstep cores and ECC, STM32 seemed to have an option to run redundant MCUs but I couldn't find a clear example.

My robot is fairly simple, I just want to find out what is the most convenient automotive/aerospace grade platform to use.

>>933761
Bumping for this

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>>933576
would this be any good for soldering?
http://www.ebay.com/itm/2in1-SMD-Rework-Soldering-Station-Solder-Iron-Welder-Hot-Air-Gun-852D-5Tips-ESD-/181139781537?hash=item2a2cc5b7a1:g:9gIAAOSwlV9WST3F

>>934471
I just got done watching this, its a different model and probably a different company but whatever its close enough.
https://www.youtube.com/watch?v=0GdV7XBae74#t=1054.640643

>>934489
I want to solder shit with a hot air gun and get into rework, and i already have a cheapo variable temp iron, i want to get a 2 in 1 that has temp readouts... i probably won't get the one i posted because all the amazon reviews are either 1 sentence fake reviews or complaint reviews about shit breaking within first 10 hours of use...
Do you know of a decent one that won't cost me a shit ton of money?

>>934198
Ic=6A @ Ib=20mA => hFE=300. Power BJTs typically have hFE below 50.

Darlington or FET.

Darlington is easier to drive from logic, FETs will have lower power dissipation (typical I*Rds[on] is lower than typical Vce[sat] at that range).

> this is for a motor H-bridge
FETs have the advantage that they conduct in either direction, so you can use synchronous rectification to avoid the need for flyback diodes.

>>934491
I have no clue, it was just chance that I was watching that.
Someone else might be able to answer that for you, I just use cheap fixed temp irons.

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If I use a Max232 to connect a PIC to the serial port on my computer, can I do something like this to blink two leds when there is data transmission going on?

>>934576

yeah, with 1K there should be no problem loading the lines down. if you wanted more brightness tho, you would put the signals thru inverters first to reduce the loading to nothing.

>>934498
Not the guy you're replying to, but is hFE the same as the beta value?

>>934645

Help

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>>933807
Alright, now I've managed to achieve this little "milestone" I've wanted to do for a while - a MIDI velocity compressor.

Works great. I set my piano to respond to MIDI messages only. So the keyboard is effectively a MIDI controller anyway, which means the data goes into the Arduino, the velocity is compressed and sent back into the piano.

Now when I accidentally hit a note too hard it isn't too jarring.

The threshold and ratio are #defined constants at the moment but I plan to write a whole suite of MIDI processing effects (harmonise, transpose, echo, etc) and build it into a nice unit with a HD44780 LCD (which I've recently got to grips with), a pot or two and a few buttons.

What is jp5 on an arduino? On my dunduino its not soldered and is a 2x2 set of pins

>>934083
I'd agree if I didn't think that general threads are generally cancer. Better to keep as much contained in one thread as possible.

But yeah, softwarefags make me REEEE

https://www.youtube.com/watch?v=NEoWaP4skv8

>>934654
Yes, hFE is the same as beta.

When threads die, remember to post a backlink in the old thread. I use clover and didn't realize it was dead until it archived.

>>934777
I think general threads are fine for board topics like this. Before /ohm/ there were tons of electronic posts that didn't need their own thread. Also /ohm/ was originally created to show off projects and help newbs get into the field.

Electronics has a high barrier of entry. Figured it deserves its own general.

>>934877
Yeah, despite what I said, /ohm/ is probably the best "general" thread on 4chan. It's just things like "/ksg/ #56,231 - hanako's farts edition" that are really awful.

Hey guys, i need something to regulate the speed of a cooling pad fan, by USB, i already created a thread but anons keep telling me that it should be me creating the circuit, so here i am...

Thank's

>>935219

does it need to be by usb?

why not just have a potentiometer/555 circuit?

How can I get a ~100v-2000v adjustable DC circuit for as cheep as possible?

I've got about 10 1 micro farad 1kv caps If I can cop a couple diodes I could make a cockcroft walton multiplier, but I still need to be able to adjust it

It only needs to be a couple of milliwatts, but I can limit the current. It's for a HeNe laser.

>>935231
Yes, but i have the female and male connectors so...

>>935219
In other words you are looking for a subcontractor?

>>935257
I don't know what that is...

Here, you have the thread >>935074

Thank you

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>>935246
Flyback transformer + regulation circuit.

Its a bastard to get stable but it works nicely once you do. Put a 27 ohm resistor in series with that MOSFET gate fast turn off diode! It causes so many problems without a series resistor.

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>>935246
If it doesn't need to be continuously variable, you can build a long chain of voltage multipliers and use some heady-duty switches to switch between the multiplier stages. That way you'd be able to select between multiples of the mains voltage. You're probably going to need more than 10 caps, though.

>>935246
Dude, re-check the datasheet of your HeNe tube. It's likely to need much more than 2kV to strike and much, much more than few milliwatts of power to operate.

>>935275

I don't have the datasheets. they are pretty old tubes I think. the stickers on the side say 2.7 mW and 7.5 mW.

This is why I wanted the voltage to be adjustable.

>>935260

How is a flyback transformer different from a normal transformer?

I have one lying around, but I couldn't find continuity between any of the pins or wires to the suction cup, probably because it is so inductive

>>935282
"2.7mW" means that the output (light) power is 2.7mW. Their efficiency is really fucking low and you're going to need something like 10W to run them.
They also need several times their normal running voltage to strike, so you need some arrangement to provide, say, 10kV output when the tube is not conductive.

>>935282
Wind yourself a new primary coil on the exposed core, 25 turns of thick wire should be a good starting point for getting 2kV out @ 12v across the primary.

I don't recommend that enameled magnet wire stuff as it often scratches off and shorts against the core.

This website uses the same circuit to drive an xray tube, the external primary coils are visible in one of the photos. http://uzzors2k.4hv.org/index.php?page=tubexray

The flyback transformer differs in that they store energy during the on stage of the primary switch and release it when the switch turns off, the energy is stored in the air gap in the core. The advantage of this is that the transformer (really a coupled inductor in this case) doesn't rely on turns ratio alone to define the secondary coils voltage.

But on the flip side you'll need a high voltage MOSFET as the output voltage IS reflected back to the primary via the output voltage and turns ratio.

That DLC network across the primary coil and MOSFET limits the peak drain voltage to something that doesn't cause the MOSFET to avalanche each cycle. I've successfully used this circuit to achieve output voltages in excess of 100kV, but obviously it can be customized to your requirements.

>>935293
Forgot to say that layout is very important for this circuit, no alligator clip leads except for supplying power to the circuit! Keep high dv/dt loops short and do use extra protection on the MOSFET's gate such as a 10k pulldown resistor and 18v zener diode.

The drain node connections should all be as close together as possible since this point is constantly swinging between the bus voltage, ground and a few hundred volts each cycle.

It is possible to get working on veroboard though, I can happily run a radio next to mine now even with a nasty 100kV arc jumping a several inches through the air when at first I was popping MOSFET's every 5 minutes because of poor layout.

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This has really spiraled out of control in complexity. I think I should have just tried to make a PCB; wiring this by hand is proving to be a tedious pain in the dick, and I'm only about 1% done.

>>935342
Ebay has some cheap pre-built adjustable high voltage power supply's.

>>934769
Read the schematics

>>935400
>implying the Arduino comes with anything else but a useless little leaflet and a sticker

>>935416
So stop buying the shit

>>933576
I want to put a regular xeon computer in my car; how do I power it? I'm usually pretty good a googling things but I keep running into pre-made solutions and reasons why using a car battery is a bad idea. I'm more of a software guy so the hardware is a little hard for me to grasp.

is it as easy as getting a cigarette lighter to wallpower adapter?

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>>935447
12v to ATX PSU, built specifically for automobile use:
http://www.mini-box.com/M4-ATX

>>935451
just curious, why won't these work?

I'm running an illumos-based OS and have no need for the windows-based monitoring software that comes with the M4-ATX

>>935463
>sorry, forgot the link

http://www.sears.com/search=inverter%2012v%20to%20120v

>>935465
Because it's hugely inefficient, which becomes an issue when you're trying to pull 100-200w from a car.

Say your Xeon system wants 120w*, a proper PSU would draw ~160w, and a regular PSU and an inverter would want more like 240w.

Cigarette lighters are good for about 80 watts, and even if you ran dedicated wiring, it's doubtful that your alternator has 240w of headroom in reserve just in case someone wants to add a blade server to it.


* personally, I think that's a bit low for a Xeon. I'll be amazed if you manage to build a Xeon that a car can power.

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>>935470
It's not a blade, just a regular desktop. I was surprised that it had a Xeon in it too as I got this basically for scrap

>>935470
http://www.sears.com/tripp-lite-tripp-lite-pv375-powerverter-375-watt/p-SPM8408280131?prdNo=1&blockNo=1&blockType=G1

this one pulls 375 watts. will this work? I drive an 07'camry with stock alternator. Trying to find the specs right now on the wattage it supports/ what the usual load is

>>935465
It probably would. But converting from 12 VDC to 120 VAC then back down to about 12 VDC is kind of retarded, and probably hugely inefficient. If your computer only draws 200 W or so, but there's a massive loss in the conversion step, you could be putting strain on your alternator and/or battery. I also wouldn't feel very safe about that computer being plugged into a cheap ass power inverter.

I just tested a small power supply circuit and had one of the rails' filter caps installed backwards. I only noticed after I started to hear a small chirp ~3s after connecting the power and immediately shut it off. Are the caps I had reverse biased ruined or can I just flip them around and power it back up?

>>935616
Polarized caps usually explode if they're put in reverse. Are you 100% sure they're not correct and the chirps are caused by something else?

>>935619
they were 100% positively installed backwards. They're big 3,300 uF caps and the markings are very clear. I'm sure they would have exploded if I left the power connected, but as it stands they didn't start smoking and aren't bulging around the vents or anything. No funny smells either, they just got a little warm.

Lesson learned, by the way: Don't drink and DIY

>>935497
Read your car's manual.

The inverter supplies 375w/600w stable/instantaneous which means if it were 100% efficient it would draw 31.5A/50A.

Typical lighter sockets supply 8-10A.

>>935623
I swapped them around and tried again. It doesn't appear that they're damaged. They're not shorted and they appear to discharge at about the same rate as the caps that weren't reversed, so their capacitance doesn't seem to have been affected by my fuckup.

>>935258
No one is gonna make a circuit for you.

Look into PWM, and make a circuit which would use a 555 timer and a small MOSFET to provide the fan with the generated signal off of the USB voltage.

>>935675
>No one is gonna make a circuit for you.
Some cuck did just that >>>935658

Need IoT microcontroller ideas that aren't the generic weatherstation crap

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>>933761
Is there any EEs here that have an opinion on this?

>>934469
>>935860
Circuit looks fine, except you're powering the MAX232 off the RS232 DTR and RTS lines. That's a common hack to get power out of an RS232 port, but not all USB-RS232 converters use those pins, and if it does you'll have to set them high in code.

>>935867
I cant take credit for the circuit,
and thanks for the response. Ill be using an actual rs232 port, not a converter.
Should there be any extra smoothing caps?
and Ive read that the electric in a car is really noisy, is there any chance the shared ground could feed extra power back into the computer and mess something up?

>>935881
You don't have anything to worry about for multiple reasons:
The car's power supply shouldn't be noisy when the engine isn't running.
When people say a low voltage DC power supply is noisy they mean the voltage is fluctuating by a couple volts or less which causes circuits to not work as intended. They don't mean it's producing voltages high enough to damage components.

You're not even connecting to the Car's power supply, you're just sharing ground.

>>935891
Ok cool, Thanks again.
This should work for now, later on I plan to work something out to monitor stuff while the car is running, for a few reasons.. one is the check engine light sometimes doesn't come on right away, and two I'm not sure what info I can get from it. I know some cars have outputs like rpm's or maybe throttle position, that would be nice to monitor for diagnostic reasons

>>935342
What software is this?

>>935900
https://code.google.com/archive/p/diy-layout-creator/

I don't even remember where I downloaded this from, but I found it on my desktop when I was looking for something to lay out through-hole components. It's a little wonky, but I like it.

>>935915
different anon here,
it looks like its double sided, but what do you use to keep the circuit from connecting both sides through the holes?
are you just using wire to connect it all?

I'm trying to build an AM radio receiver. I need it to tune in to 8Mhz. Is there aby way to avoid using an LC circuit and use a crystal oscillator for a demodulator/ tuner? If anyone has a schematic it would be a big help.

Band pass would be the most simple choice. I'm curious as to why you wouldn't want to use it?

>>935977
Meant for >>935934

>>935934
Also don't forget to put a high pass filter after the antenna to filter out any DC components

>>935979
>>935977
Well I found an odd little single crystal oscillator AM transmitter schematic floating around on the web. And wanted to try it out. But after some fiddling testing it with an oscilloscope and frequency generator to make sure it's working. I found that I simply don't own a radio that can pick up shortwave. (I have a radio licence for work so it's all legal, but I don't own or operate a radio)
What I ultimately want to have is a set of receiver transmitter circuit boards. No particular use for it, just want to learn a bit from the process.
I figured I could use a crystal ladder filter type of receiver? But all the radio schematics google spits out are foxhole radios made by hipsters.

>>935934
You could get a microcontroller and a 20 MSPS analog to digital converter and make a software defined radio. Just a thought. If i finish my work quickly I can come back and suggest some analog solutions

>>935934
if you are wanting a simple am radio look into the "three penny radio".
8 mhz is oddly specific, mind me asking what you want to do?

>>935447
> I want to put a regular xeon computer in my car; how do I power it?
Alternator, battery, inverter. This is standard kit for RVs, but you may have trouble installing a decent-size alternator in a car.

> reasons why using a car battery is a bad idea.
It probably doesn't have the energy capacity to run a PC for very long.

Car batteries are designed for short bursts of high current (starter motor) and long-term trickle current (running the radio or side lights with the engine off).

For sustained non-trivial power consumption, you'd need a deep cycle battery with sufficient capacity (how much power does the PC draw and how long does it need to run before recharging)? You may also need a bigger alternator than the one which came with the car if you want to be able to recharge the battery in a reasonable amount of time.

> is it as easy as getting a cigarette lighter to wallpower adapter?
No. You aren't going to power a desktop PC from a lighter socket. The 12V current will be 10x the 120V current (plus some extra due to inefficiency).

>>933576
Where do I get started, whats a good absolute beginner project?

>>935919
Exactly that. it's just blank perfboard from radioshack with no copper on it. I'm using solid 20 gauge for wiring power supply and other high current lines, and 26 gauge enameled wire for signal lines where space is cramped and shorts are more likely. But everything is wired point-to-point.

>>936163
What do you want to do?

>>936163
555 LED blinker

>>936168
At least understand why my car lights aren't working. But I just don't know where to get started, I wouldn't even know what I'd want to do. I'd really like to learn about resistors and basic stuff while getting hands on knowlege

>>936060
>>936064
A "three penny radio" isn't a solution I was looking for. It's a variation on the foxhole radio with a transistor but thanks for the suggestion.
I use 8Mhz because it's the lowest value crystal oscillator I can buy locally and since online stores don't ship to my 3rd world shithole or charge an insane amount of money for shipping I'm stuck with 8 Mhz. It is also I band I know wont disrupt local radio traffic unlike a 10 MHz+ which might piss off a HAM operator or two.
I'd be happy if I could transmit a few words across the room with it. I'm not looking for something fancy just simple. All the local analog to digital converters and SMD. And I'm not confident enough in my soldering ability to work with such tiny components. DIP are fine tho.
What I'm looking for would be something that has:
A fixed AM band reception at 8Mhz preferably with a premade crystal oscillator or LC circuit with premade parts. (I can never get the inductor coils to function right)
Can demodulate said AM (germanium diodes are super effective)

>>936183
Look at the pastebin link.

http://pastebin.com/9UgLjyND

Also, figure out what you want to eventually do. Figuring out why your car light doesn't work is a good place to start.

Look at some videos / tutorials showing the relation between current, voltage and resistance.

>>936180
>>936163
Then amend it with two alternating LEDs.

>>936183
Perhaps a blown fuse or bulb? A car isn't really the place to go fiddling as a first timer as it could lead to a life and death situation if something stops working on the middle of the motorway.

>>933576
/ohm/ dedicated board when ?

>>936340
It would quickly turn into a tech support board with /v/irgins wanting step by step instructions on how to solder a CPU.

At least "diy" implies doing your own dirty work.

>>933637 Here


For anyone wanting to get into PIC: do not enable LVP when programming the mcus.

>>936340
Geez, anon, /diy/ is slow as shit, /ohm/ included. Why split a slow board into two even slower boards?

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>>934756
>no decoupling capacitor

>>936356
> never use decoupling caps when prototyping
> never had a problem, circuits all work great
> time to produce
> better add in those capacitors so production house don't laugh at me behind my back
> no change to device operation.
Well worth the pennies to avoid ridicule however

>>936356
he's using a 'tarduino, why are you surprised?

>>936393
better to have and not need than to need and not have

>>936356
So fucking what?! Is that how you get your validation - trawling threads so you can fascetiously point out trivial mistakes?
>>936393
>Well worth the pennies to avoid ridicule however
I hope you're being sarcastic.

Because, yeah, if I somehow came across a time machine, I would totally use it to tell my past self to put a capacitor on the breadboard before taking that photo to spare myself the humiliation so evident now.

Why? Why didn't I put a cap on it? They tell me it could happen to anyone. The best of us, even. Yet I still lie awake at night, tormented...

>>936496
True enough. Better to have had to have used it than to have not have to have had to have used it, only to had have ended up having to have needed to have had it...

>>936246
Im under the impression that am is for long distances, you mentioned just transmitting across the room.. a low powered fm transmitter could do that on any frequency you wanted with an absolute maximum range of <50 feet. Usually those only get about 5 feet or so before the signal is intolerable.
My measurements are based off of the shitty fm transmitters I had years ago. for all I know they may have made a break through that would allow whole house transmission for a cheap unit by now.

>>936496
>better to have and not need than to need and not have
holy fuck, someone doesnt understand capitalism and modern manufacturing methods

>>936505
Indeed. These days it's more like "better to sell a hi-fi deliberately designed to break after about 4 years than to sell one that lasts for 40 years"

>inb4
>hi-fi

The difference between an engineer and a hobbyist is a decoupling capacitor.

>>936505
My manufacturing methods are the furthest thing from modern, and I only make shit for myself, and I want to be absolutely sure it works correctly.

ie. >>936532

>>936500
no i mean if you do this kind of thing for a living and you send a design away to a fab house and they see you don't know shit about circuit design 101 they might shaft you.
you dont walk into a car showroom and tell them you dont know anything about cars but you have x amount to spend.
for a personal project or development then as long as it works idgaf, if you are sharing your work you should obey best practice so people think you know what you are talking about.

>>936570
>people think you know what you are talking about.
But I don't. I'm pretty new to electronics but the few circuit boards I have made (and posted here previously), I have put a cap on the IC.

>>936503
Yeah but building an FM transmitter is way more complex than AM. Like I said I have a simple little AM thingy built. Now I just want to pair it with a receiver. Was thinking about the tuning LC circuit in an AM radio with an 8MHz crystal and using a diode for demodulation.

I would usually ask these questions in the local radio club. But since I had to fail some of their repeater gear a few weeks ago for disrupting cellphone traffic. I think they might still hold a grudge against me :/

Need to rework some smd packages on a motherboard. So that means I need
H O T A I R
O
T
A
I
R

Recommendations for a station under $200?

>>936650
Drill a hole in your skull and you'll have an endless supply

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>>936650
pic related should do.

on a more serious note, if you're only using it once, anything that won't be DOA will do the job. One was posted earlier in this thread.
Can't think of any that are below $200.

>>936650
>set oven to 480f
>put pcb and oven thermometer in a glass pan
>open and close the door to regulate temperature

>>936671
U don't like EEV Blog m8?

>>936590
I've had a really bad day. Sorry if I come off as a prick.

Building a frequency modulated transmitter is no more complicated then an amplitude modulated transmitter.

I used to bull's-eye womp rats in my t-16 back home. They're not much bigger than 2 meters.

For frequency modulation just place a charge across a diode to vary its capacitance. Put the diode in the LC circuit and run the audio amplifier to the diode.
Varying capacitance changes the frequency.

Amplitude modulation, you have a stable oscillator and probably modulate the power going to the buffer amplifier or final amplifier.

Failed their radio gear?

>>936703
are you replying to your own post to further reply to me, or are you replying to the person that asked the question?

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>>936703

>>936708
Post 936703 was my first post in this thread. It was in response to 936590's comments about FM transmitters being more complicated than AM transmitters. Polite Sagebrush.

>>936716
Welcome to 4chan, newfriend

>>936716
oh ok, I'm >>936590.
I didn't take any offense to what you said. But thanks for actually apologizing.

I'm in my final semester of my AS in Electronic Engineering Technology which will basically qualify me to be a technician. It's basically half of a real EE degree at about a 1/10 the cost. Anyway since I don't have previous work experience in EE it'll be hard to get my foot in the door. I'm thinking about getting my NERC cert and applying for jobs in power distribution, (supposedly having it helps a lot as it means companies have to waste less time and money training you). I was just talking to a alumni today who was hired with Eversource. He says you get about a year of training, 4 months classroom and the rest in the field which is good since my electronics background is mainly small signal stuff. I'm getting off topic, should I get my NERC cert and where can I get some good study prep material for the exam. I only want to pay the $600 once.

Unrelated question:
I'm doing a design project for one of my courses and I need to synchronize a switched capacitor bandpass filter and mux. It was recommended I do this with an MCU but I have no microcontroller experience (though I'm currently taking a class on it). Is there another way to do it and if the MCU is the best how hard would it be to pick up and learn to program, at least for what I need to do for now. In class we're using PIC microcontrollers and programming in BASIC but I don't know if there's better stuff I should be using.

Do all walkie talkies use the same channel presets?

Like does channel 1 in one brand also correspond to channel 1 in another brand?

>>936783
Very likely. "Privacy tones" may not.

>>936697
Not that anon, but I'm a graduated EE.
He knows his stuff, but he nitpicks everything. He draws attention to small nuances that don't really matter, also lately he's been getting way too political on his channel.

For example, he'll make a big deal about the brand name of a capacitor when in reality the brands don't really matter for electrolytic capacitors. They're made to be cheap to begin with, not worth ranting for 5 minutes about it like he does. Another time he got a prototype model of some all in one medical pc, he know it was a prototype model too, and he tore it a new one for being sloppy. Granted, it did have some oddities even for a prototype like a random useless battery.. but sloppiness is to be expected in a prototype. He used to break down how things worked within a device. Now he just complains about anything that's not siglent or fluke.

>>936845
I agree. He thinks that everyone needs thousands of dollars worth of equipment even to perform the most basic of tasks, he'd probably tear me a new asshole too if he saw my "lab" equipment.

The most expensive thing I own is my Rigol DS1052E scope and to be honest I wish I'd have gone for a cheaper offering. Its nice but it really doesn't get used all that often and when it does I probably use about 20% of the features.

>>936851
>The most expensive thing I own is my Rigol DS1052E scope

Meant to say its the most expensive piece of lab equipment I own*

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don't know if this is the right place to ask this,

I don't know much about electronics.
I'm curious about t8 ledtubes and have aquired 3.
I have a cable with wich I can hook one of the lamps straight to a multisocket.
is there a cable with wich I can connect a further tube to the first one , so both work, or do I have to feed the second one back into the socket.

also, is there a cable equivalent that I can use to hook one up to the cables that come from the wall , like I would normaly hook up a lamp ( sorry for the weird way of saying this, german here) is it maybe a g13 socket ?

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What is the proper way to use PNP transistors?

On a breadboard circuit I connected the Collector to 5V and the load to the Emitter pin. It works, but looking at schematics everywhere it seems like I'm supposed to connect the Emitter to 5V and the Collector to load->ground when sourcing current. Either way works, but in the simulation apps the voltage at the beginning of the load is slightly lower when it's connected to the emitter (transistor is reversed?).

Ignore the fact that on the schematics the grounds are pointing up, I know you're not supposed to do this and I don't do this in general.

>>936872
A shows the correct orientation.

If being used as a switch connect the pull up resistor directly to the base and use a much large value, about 10x the value of the base current liming "on" resistor.

>>936872
You can reverse collector and emitter in some cases, but transistors generally work very, very badly collector and emitter swapped and this is why it's practically never done.
So, like the other anon said, A is the correct way.

>>934051
Opamps usually can't provide enough current.

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>>936703
Must have been a long ass day anon.

Like I said I already have an AM transmitter made out of a audio amplifier, crystal oscillator, and RF amplifier. Now I just want to pair it with a receiver. I figured I could use the circuit as in pic related.
Could I just replace the tuning LC circuit in an AM receiver with an 8MHz crystal and keep the rest of he circuit the same?

And about the Failed gear.
If you want to have a decent powered transmitter you need to have it certified every few years depending on the type of transmitter.
Well I moonlight/work for the instituted that gives said certificates. And I flunked some repeater gear used by the radio club, since it was no longer up to standards. They took it kinda personally.

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>>936697
He makes a living out of it, and I can respect that. However; and this may be more a result of his audience, last year he stopped doing anything more than complaining. He used to teach. He used to discuss. His early videos, although lacking in production value, had some definite content to them. Now he just 'entertains' by opening his mail, dismissing most equipment subjectively and with prejudice, ranting about capacitors and at the time I stopped watching he was in an ongoing feud with a batterizer company. Increasing popularity may have caused him to move towards less esoteric discussions, killing worthwhile content in his videos. But hey, if you like him, that's cool too.
>>936845
>>936851
Interesting. I though I was alone with this opinion of him.
His forums are alright if a thread has already developed.

If I'm interested in getting into electronics(electronics, not Arduino software stuff), is there a good book to get to learn from? A lot of industries have a "This is THE book, it will teach you everything you need", is electronics like that, or is it one of those hobbies where I'll be looking up explanations online and reading through a bunch of overpriced books, before regretting not just taking a class on it?

>>936944
no. try the art of electronics. From what I've read thus far, it seems to cover everything decently well.

>>936941
case in point:
https://youtu.be/yPdeAk17Vys

>>936945
The OP pastebin has that as a book for advanced stuff. Does it teach beginners well too?

>>936950
If you have taken at least calculus 1 (differential and a tiny bit of integral) it will work wonders to your understanding of how things work. Otherwise, it's a matter of plugging numbers into given equations.

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Is there a more succinct term for "helping hands"?
On Amazon all I find are this garbage.

The way I'm familiar with the term, they're just really stiff wires with alligator clips on them.

>>936951
Anything about radios in AoE?

>>936961
I vaguely remember there being something in the last few chapters of the second edition. Haven't skimmed far enough into the third one yet to say for sure.
Wouldn't a book specific on radio electronics and concepts be better suited?

>>936965
Probably

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I de-soldered this IC from an old IDE disk drive. The code says that it is a 64-megabit SDRAM memory chip (4 x 1,048,576 words by 16 bits). Is there any way to use it with an 8-bit microcontroller? Such as logging data or something.

>>936957
your picture is helping hands.

what you might be thinking of is stiff wire with crocodile clips on them.

>>936980
if you cant find a datasheet or figure it out from the pcb you might have a hard time
a sensible manufacturer may have other similar chips that are drop in replacements or at least pin compatible to help you.

>>936980
You can use GPIO to produce the required signals. It isn't particularly difficult, but it isn't fast either.

>>936983
Sorry I forgot to paste the device code. It's hard to see: K4S641632H-UC60

>The K4S640432H / K4S640832H / K4S641632H is 67,108,864 bits synchronous high data rate Dynamic RAM organized as 4 x 4,194,304 words by 4 bits, / 4 x 2,097,152 words by 8 bits, / 4 x 1,048,576 words by 16 bits, fabricated with SAMSUNG′s high performance CMOS technology. Synchronous design allows precise cycle control with the use of system clock I/O transactions are possible on every clock cycle. Range of operating frequencies, programmable burst length and programmable latencies allow the same device to be useful for a variety of high bandwidth, high performance memory system applications.

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I'm relatively new to electronics. What is the quickest and dirtiest way to drive a seven segment display with less pins?
I'm using an Arduino Uno (my Mega 2560 hasn't come in yet) and I need to run several 7 segment displays at once to display temperature.

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>>937010
Shift register
https://www.sparkfun.com/products/13699

>>937013
Awesome. Thanks!

>>936776
I don't know anything about pic, but atmel's mcs can be programmed in C, and if you want to be a basic bitch you can also put the arduino boot loader on there and you can even buy them with the boot loader already on there.

>>937010
>>937013
>>937014
Also handy for LCDs and LED matrices.

>>937029
I know C is popular but I've never programmed in it. I've really barely programmed at all.

The extent of my programming knowledge covers entry level visual basic and labview if those even count as programming languages.

I would basically need to be able to pick up this micro and be able to program it to do what I need in 2 weeks or so. It has to do two things: output a PWM signal where the duty cycle will change over fixed intervals of time to one of 10 or 15 discrete values. It will do this incrementally and when it hits the last value it'll return to the first (this creates a changing center frequency output on the LTC1059). In addition the MCU has to go through a binary count sequence on the address select pins of an analog demux to cycle through the inputs in order and return from the start. BUT the frequency at which the PWM signal changes its duty cycle AND the frequency at which the MCU counts through the different I/O pins on the demux has to be exactly the same. They need to be in sync.

I know what needs to be done but have no knowledge of how to implement it. I can only hope this functionality isn't too hard to code or that I can find code that someone else wrote and modify it to suit my needs. I don't know if this would be easier in C or BASIC.

>>937048
Just learn the C versions of the BASIC programs you've already made. A simple program is a simple program and, porting such a program to C would be a simple case of substitution. The logic wouldn't be any different.

>>937048
>>937066
Well its doable to learn c that fast but its hard to just guess if someone is actually capable of doing it that fast or not.
If you think your good give it a try,

if visual basic is a real programming language and not some scripting bullshit post the code you have and I or someone else might convert it to C for you. Im not saying its doable but Ill take a look
You might have to change the functions though

>>937114
>>937048
The only difference between VB and C is that VB has garbage collection and syntax invented by Satan himself.

>>937125
... so mexican legos?

>>937114
Yeah it'll be a kind of "linear transformation" if you like. When you see

>Dim foo As Integer

replace with

>int foo;

When you see

>For i = 0 to 30
>...
>Next

replace with

>for (i = 0; i <= 30; i++)
>{}

etc, etc. Just reading up on some C syntax ought to make all the lines easy to translate for simple programs. That in itself will be a learning experience. Maybe from there he would feel confident enough to continue in C for other projects.

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>>937125
>is that VB is garbage itself

Fix'd it for you


What kind of BASIC runs on basic stamps?

>>936873
>>936880

Thank you. I built a relay module using PNP transistors with the correct orientation, just for fun and to use some of the comically oversized LED's I have. Is there any advantage to driving relays with PNP rather than NPN transistors?

>>937147
Yea, more people need to realize the superiority of C as oppose to lego languages.
I saw some of the syntax for basic and it looked easily translatable so I figured fuck it I might was well offer to help the guy out.
He isn't begging for someone else to do this, and there really isn't much point in learning a language for a one off project. I'm sure knowing C would help him out later on though

>>937048

Get an arduino, buy an extra atmega 328p-pu with the arduino bootloader, put it in the dip socket, program it and transfer it to a final board if it's requried. This is the easiest way to do what you need to do.

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>>937183
Yeah I started on BASIC on the ZX Spectrum +3. Then when I got my first PC I moved onto GW_BASIC for DOS. I have fond memories of it but now the language seems utterly ridiculous to me.

Just look at how hideous that code is. I know Visual Basic does away with line numbers and lets you use braces, but it's still a poor language.

>>937183
>>937114
Maybe I wasn't clear. The project I'm working on right now has no coding of any kind done yet. It would all be from scratch. I have programmed vb stuff in the past for a bullshit class I was taking but it has nothing to do with what I'm working on now. I don't have a program written in vb to convert nor would I know how to write one, I don't remember much of the content from that class.

I was basically trying to say that I have zero knowledge of coding in any language and the only thing I pulled from vb was a few fundamentals like declaring variables and how loops work and stuff.

I appreciate the offer to help though. It seems like some people are saying I can probably learn enough C to do what I want soon if I apply myself. My project is a design project for a class and I have to design the board, order components, breadboard it, and design the PCB in orCAD/PCB editor. After that the design gets sent out for manufacture, when I get it I solder the components, test it, build an enclosure, and present it. I need to get the programming done soon so I can move ahead in the process of getting it built. I'll talking my advanced digital and microprocessors professors tomorrow to get their input on the feasibility of picking up the coding quickly and possible alternatives if I can't.

>>936671
G'DAY M8s, HOW BOUT A BLOOMIN ONION ON THE BARBIE? HERE, LOOK AT MY RETARDED KID!

>>937048
For low-level stuff like this, I prefer using assembler.

FWIW, I think the "half an EE degree" is an exaggeration if you're only taught VB and LabView. I did one year of EE before switching to CS, and we did Pascal, C, 6502 asm and 68000 asm in that year.

Knowing assembler is essential for EE stuff. Even if you never program in assembler, you need to be able to read and understand disassembled machine code, as that's what the CPU is actually executing.

In CS/SE, you can get a long way without knowing any of that stuff. In EE, you can't.

>>937186
BBC Basic sucked less (e.g. DEF PROC / DEF FN rather than GOSUB), but it still sucked enough to provide a big incentive to learn assembler.

>>937271
VB wasn't part of the EET program at all. That was something I wasted my time on and kind of regret. Labview was though. For Microcontrollers we're using the PIC18 and I guess the IDE, MPLAB, supports assemblers and C/C++ compilers. I assume that means it supports programming in those languages and while I'd rather learn C but we're learning BASIC because my professor is older than dirt and got his start in Electronics in the 50s or 60s therefore he thinks the way he learned it is the best way to teach it. I think in advanced digital we touch some some VHDL/Verilog and maybe some C/C++ stuff as well towards the end but I'm not sure to what extent. Probably not in a great deal of depth. The degree doesn't make me an engineer but more of a technician. I assume when I transfer into a bachelors EE program one day that they'll cover this stuff much more in depth.

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>>936894
Today was even worse.

I have never seen it done that way. The antenna would change the frequency. You may want to loosely couple the antenna in to the circuit instead of directly, for the best chance of it working. I would try it. Worst case is that it doesn't work.

Trying a simple regen circuit may be the way to go.

ok, i have test in 2 days. They include the following:

1. DC diodes
2. Rectifier
3. DC power supplies
4. Bipolar junction transistor
5. Bipolar junction transistor switch
6 Bipolar junction transistor biasing
7. Common Emitter Amplifiers
8. Common Collector Power Amplifiers
9. Field Effect Transistors
10. Operational Amplifiers

ask me questions about these topics, please keep it general and not TOO specific.

i want to know what kind of shit you guys will come up with and answer it

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>>936894
Me again. GF now on top of me. And drunk.

So, If you have the crystal. Maybe try a crystal colpitts oscillator. Pull the frequency as needed with a varicap.
Take the antenna and inductively couple it to a diode and also couple the diode with the oscillator. This will provide a direct conversion to audio if you are bang on frequency. Audio amplification may be necessary.

A few more shots and here you go! A real schema for a real human bean.

>>937328
How do DC diodes differ from other diodes?

>>937335
Probably just diodes.

>>937328
http://pastebin.com/9UgLjyND

Find some youtube tutorials on those things.

So I'm fairly familiar with electronics. I've been a hobbyist since I was young and I'm in my 4th year of college doing EE and CE.

As it is, electronics is a pretty difficult subject to get into. Most of the books available are geared towards EE students or an academically inclined studious audience. There aren't many YouTube channels, that I've seen anyway, that are purely dedicated to teaching electronics and the ones that are usually aren't geared towards the layman. So, I kind of want to start a channel that'll do that for two reasons. Mainly because I believe electronics should be more accessible, but also teaching material is the best way to remember the material so it'd better myself as an engineer as well.

I already have a channel I post my projects to, should I create a separate channel or just put it on that one? I don't like the idea of splitting channels, but at the same time, I don't want my educational series getting muddied by my project videos. Also, any suggestions on what topics I should cover first, kind of as a pilot for the channel? I was thinking about just going through Art of Electronics and basically making my fundamentals series as a deconstruction and explanation of AoE's material then doing more specialized stuff in the future.

>>937344
AoE is pretty advanced for introductory material, I would say.

>>937170
>Is there any advantage to driving relays with PNP rather than NPN transistors?

No, not really.

>>936957
3rd Hand

>>937328
>1. DC diodes
What is the reverse breakdown region?
What is the forward voltage drop, and what is the general forward voltage drop for silicon diodes?
>2. Rectifier
What are the 2 basic types of rectifiers?
What are the output voltages of the 2 basic types of rectifiers relative to the input AC voltage?
>3. DC power supplies
What is the difference between linear and switch mode supplies?
Differentiate DC power supplies and Rectifiers.
>4. Bipolar junction transistor
How are BJTs rated? What does hFE mean?
What are the major operating regions for a BJT?
What are the major applications for BJTs?
>5. Bipolar junction transistor switch
What two regions of operation does the BJT switch operate between?
Generalize the operation of the BJT into a 4 word title.
>6 Bipolar junction transistor biasing
(Can't think of anything off the top of my head)
>7. Common Emitter Amplifiers
(Can't think of anything off the top of my head)
>8. Common Collector Power Amplifiers
(Can't think of anything off the top of my head)
(Its been a while since I've studied transistor amplifiers)
>9. Field Effect Transistors
What's the main difference between BJTs and FETs?
What are the two main types of FETs with regards to their zero-biased state?
Generalize the operation of the FET into a 4 word title.
>10. Operational Amplifiers
What are the two main operating modes in which OP-amps are used?
Build a band pass filter using OP-amps

That's all I got anon, hope it helps!

>>937335
He divided diodes into DC operation and AC operation.

>>937170
You can use PNPs as (better) high side switches, allowing you to ground the other ends of the relays. Yeah, that's usually not particularly important, but with some loads it is very convenient to have the other end grounded.

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help me.
first time on this board.
i have electronics exams in a week.
i gotta learn from diodes,transistors,sources,op-amps(inverting,sum,etc..),rectifier(from simple diode to the 4 diode ones and a few mores) and more stuff like this.
Atm i know how diode works,transistors ,capacitors etc... and i know how to solve electric problems.
What is a good book that can teach me these staff as fast as possible?
I will get at exams from simple problems as :"write diode certain graphs " to problems with "polarization of common emitter amplifier with resistor divider" and problems with 2-3 op-amps and negative feedback with resistors,some diodes etc.. and gotta tell the output voltage or calculate resistance etc..

>>937473
Why don't you use whatever textbook and/or support material the course uses?

>>937475
Hahha,textbook.
I live in eastern Europe.here electronics/electrical engineering are teached by communist 60+ teachers.
.

>>937479
Whereabouts? Also, why would it matter if they are old communists, the subject of yours is basic analog electronics, not some propaganda. Also, it should be fairly easy to get some books on the subject

>>937482
It is basic analog circuits but i cant find any book in my language that is not old full of integrals and calculus in general.
I need plain and simple ones,like what happens if i put a resistence on the negative feedback on an op-amp ,i dont have time to learn to calculate performance lmao and electronics is not my major either.
Got any english books ?

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>>937484
>electronics
>without calculus

>>937484
well, you see, the no-maths approach is hip and shit, but there is a problem with it, you won't feel the magnitudes, unless you get into the dirty math part, that's analog electronics for you
>like what happens if i put a resistence on the negative feedback on an op-amp
Well, you see, nothing, because what configuration is the opamp in and etc etc, you need moar info about the whole stuff to put it in perspective and even make a proper question out of it.

>>937488
its just a course,i am not electronic engineer,i will never use this shit but here the programe,you cant choose your courses.
The hardest ones i get are some op-amps with normal diodes,zener and maybe 1 transistor and tell the output voltage of the circuit or calculate some resistences to work in the given voltage and stuff like this.
What is a beginner book into this stuff?

If you have a huge electrical machine and you're trying to find its reactance and shit, is it generally calculated by direct measurement of reactive power and current and stuff or are there industrial equivalents of the little LCR meters you use in electronics labs?

I work at a lab where I repair very expensive oscilloscopes, spec ans, gens, etc

I literally did no school, and am just using the troubleshooting and service sections of manufacturer manuals

Pay is good, been here for almost 4 years now

>>937516
There are meters that will tell you voltage, current, power and phase angle. With machinery, you generally need to measure that stuff while it's running because it will vary with speed, load, and (to an extent) temperature.

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Next to no idea what I'm doing...
Basically, trying to get this to work. Output from the receiver is 4.8v when on the pad, however when the receiver is connected to a device I get nothing. Voltage then drops to 1.2v.
Tried input to the pcb as +/gnd +/- and micro USB. How can I get it charging?

>>937569
Could be over current protection kicking in? Try it with a lower power load.

>>937569
Is AC being sent to the coil?

>>937170
>Is there any advantage to driving relays with PNP rather than NPN transistors?

Depends on your circuit and drive requirements, NPN lets you have the transistor referenced to the negative rail with the driver sourcing current whilst PNP is the opposite.

It's not much of problem these days with totem pole type outputs in a micro controller but it could mean the difference between an additional transistor being required in a minimum cost circuit.

>>937587
With a NPN can I low switch a 5V relay using a 3v3 signal?

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>>937592
Like this? If so yes you can, that's actually one of the benefits of bipolar junction transistors over MOSFET's. They are current controlled so it doesn't matter if you are only driving the base with a low voltage supply.

>>937596
Also don't forget to put an anti-parallel diode across the relay coil, anode to collector and cathode to +5v.

>>937186
That was before my time, I can understand and make sense of the code though.. Im not thinking it though enough to know what the fuck it does.. some bullshit get input, do math, beep if in range, else do math agian untill in range to beep.
idfk what the fucking point is though.

But overall Its not the worst language Ive seen, actually appears usable for light applications.

>>937331
>lm386 because thats what the kids are into
kek

"its all about the lm387 now.. get with the times grandpa"

>>937488
nah man, just put resistors and diodes everywhere and hope for the best

>>937578
>over current protection
inb4 "thats not how current works", "blah blah only draws the current it needs"

>>937280
The Spectrum had DEF FN as far as I recall. I never used it though.

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Newb here, i would like to use these old transistors as an oscillator for my power board on my brand new metallic particle accelerator, but they are bipolar, any educated guess?

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I tried to used the whole board as a single NPN transistor but ended up failing,
I could draw a schem of the board to help visualize it, all the resistors are 68 ohm

>>937715
>particle accelerator
Why do you need particles accelerated?

>>937721
Because calling a coilgun a coilgun here would tag me as /k/ supporter, which i'm not.

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And hell, i'd like to charge this beauty to the max.

>>937730
You'll need to produce 2200V. The voltage stored in a capacitor is the voltage you charge it with. What the voltage rating on a cap tells you is the maximum voltage that can be used without it exploding. A diode voltage multiplier is the simplest way to generate the high voltage you want.

>>937730
just use a lightning bolt

>>937724
particle accelerators and coil guns are not at all the same thing.

>>937724
Calling a coil gun a particle accelerator makes you sound retarded.

Would you rather be a gun supporter or a retard?

Why do people use transistors in analog radios instead of op amps. Wouldn't op amps be more effective amplifiers?

>>937757
op amps are made of transistors anon
And no, not really. They tend to be more restricted in bandwidth and current capacity in addition to being more expensive. Hell, even tubes are still produced and used for very specific applications like in high power radio transmitters.

>>937762
Well yeah lol but the schematics for radios that I have seen use actual single transistors.

I figured it had to do with bandwidth and current restrictions though. Interesting about the tubes though!

>>936356
dude its midi, what kind of dip can a 470ohm and an optocoupler make?

sure,slap on a few nF for peace of mind later on, but why worry about it on the board?

>>937768
In addition to what anon said, building an ordinary radio using opamps would be a weird half-assed solution. If you're going to use ICs, then use ICs which are actually meant for the job. There are plenty of ICs for that purpose, including ones which contain everything in a single chip. Google TDA7000 for example.

>>937873
I should have known there would be dedicated IC for radios. However, I'm coming at it from more of an educational view. I don't know much about them so I was wanting to try to build a few very short range am/fm transmitters/receivers to play with and learn how they work and such, so I figured transistors and op amps would be a good start

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Hello /ohm/

I know a lot about digital circuitry and microcontrollers. But I wanted to try my hand at power electronics and stuff.

I'm making a simple switching power supply that should be able to supply 0 - 30 volts (or somewhere close to that) at ~5 amps max.

This is the design I've managed to come up with, note that i haven't googled anything and I just wanted to see if I could make my own circuit.

Some questions I have about this design:
1. Will this work at all?
2. What are limitations to this design?
3. What value of the smoothing capacitor and the capacitor at the output of the 7805 should I use? (C1 and C2)
4. The digital controller will simply read an input from a potentiometer and produce a 5 volt PWM wave which will drive the MOSFET. Should this work?

>>937914

that's a PWM circuit, it has none of the characteristics of a switching power supply, which is a control loop that adjusts the duty cycle in response to varying loads. anyway, there's no need to re-invent the wheel. TI, among others, make a wide range of SMPS chips you can use just by following the data sheets. I believe there's also an online wizard where you just define your needs, and a circuit is generated for you.

>>937919
Wait what, I thought switching supplies were simply PWM generators. Fuck my concepts are twisted.

>>937768
> the schematics for radios that I have seen use actual single transistors.
The kind of schematics that get circulated tend to be "educational" designs. Commercial designs just use LSI chips.

>>937925
> Wait what, I thought switching supplies were simply PWM generators.
No. You need some form of PWM to control the switch, but that's only part of the circuit.

A SEPIC can run "blind" (no feedback, the output being dictated by the duty cycle), but most switching circuits need feedback for regulation.

Basically, SMPS design comes down to:
1. Choose your topology (I suggest starting with a buck converter).
2. Choose your control circuit (dedicated SMPS chip, microcontroller, 555).
3. Choose your operating frequency (higher frequency = smaller magnetics but fast switching becomes more important).
4. Choose your components.

>>937744
But it doesn't say 1.21 jiggerwatts on the label.

>>937344
I picked up AoE as a supplement to my second year of EE courses, and it's still more advanced than much of what I'm being taught. A freshman text might make a better introduction for the layman. I've found Fundamentals of Electric Circuits by Alexander and Sadiku to be decent in that role, and you can find a pdf on Google easily enough.

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how can i force my crystal to oscillate on a certain harmonic when using pic related? in my case it's a 20/40/60/80/100 MHz crystal

i probably have to utilize a bandpass filter with the resonance frequency around the desired harmonic. i thought i would have to replace RL with said bandpass but it didn't work out

>>934756
I've been making progress on this. I've hooked up an HD44780 display controlled by a shift register and a pot (currently just controlling the threshold but I will add ratio and make-up gain, along with a pushbutton interface to cycle through parameters).

I've decided to look into timer interrupts for a constant sampling rate.

Right now I've chosen an 8kHz frequency at which to check the serial port. 31250 baud is just under 4kB/s so I figured 8kHz ought to be enough. The worst case scenario would be a 4 bit lag between a byte received and processed.

What do you reckon? Should I up the sampling rate at all?

Also, shall I use the same ISR to poll the pot and buttons? Or should I use another timer, perhaps set at a lower frequency?

Are ISRs interruptible in themselves? I don't want the parameters changing while it's performing the compression logic on an incoming byte.

>>938088
>Are ISRs interruptible in themselves? I don't want the parameters changing while it's performing the compression logic on an incoming byte.
Having said that I suppose I could just store the parameters in temp variables during that "critical section".

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This type of switch has both a default on state when pressed by using a left or right pin with the middle one, and a default off state when pressed by using the right and middle pin, yes? I'm thinking about using these to toggle my cupboard LED lighting when you open the door.

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>>938092

yep, it's called a SPDT push-button, and it works sorta like you said: when pressed, the center makes contact with one side, when not pressed it makes contact with the other side.

>>938088
>I've chosen an 8kHz frequency at which to check the serial port.
I'm sure your controller has serial port interrupts so that you get an interrupt whenever it receives a character. So no, don't use the timer interrupt for the serial port unless you have some really good reason for it.
>shall I use the same ISR to poll the pot and buttons?
That 8kHz interrupt? It's pointlessly fast for UI polling. So again no, unless you have some really good reason for it.
>Are ISRs interruptible in themselves?
Not by default. You can usually re-enable interrupts inside an ISR, though, but it's generally a bad idea. Some processors also support a non-maskable interrupt, which is capable interrupting the other interrupts.

>>938109
>I'm sure your controller has serial port interrupts so that you get an interrupt whenever it receives a character. So no, don't use the timer interrupt for the serial port unless you have some really good reason for it.
Ah, good point. The main purpose for it was for a uniform polling interval without using millis () or (god forbid) delay ().

I realise that 8k would normally be too fast for UI stuff but seeing as I was already using that frequency for the MIDI, maybe I should just put it in there, unless there was a good reason to put it into its own ISR.

How should I get a constant MIDI sampling rate then? Or isn't it that important, seeing as it's going to be receiving MIDI data on a completely arbitrary basis (i.e. whenever a piano key is pressed)?

>>938100

That's just what I'm looking for, then. Thanks!

>>938111
I don't know what you're really trying to do, but if you have some important sampled thing like an oscillator running at 8kHz, you could handle the midi messages and possibly the UI in the main program and just set ISR-friendly variables accordingly. Then your ISR would just use those variables at its own convenience.

>>934012
The ability to remotely power cycle a problematic piece of hardware is awesome.

I had to do this for a single outlet, not a UPS, but the same idea. Shitty network connection at one location was DSL, and nothing else was available. DSL modem freaked out randomly every week or two, because the intermittent connection drops (Thanks AT&T business internet). I had things setup to cycle the DSL modem by cycling its outlet after a certain amount of outage.

Saved my butt from having to drive out there many times.

>>938130
The 8kHz idea was just to check for data often enough. The byte rate of MIDI is about 4kHz, so I thought if I doubled it then it will never get to a byte more than 4 bits worth of time after the completed byte.

I'm probably overthinking it. Unless you're playing huge chords then it's unlikely that the MIDI stream will come close to using the full 31250 baud rate. And even when it does, it will be in very short bursts.

It works though, but I might just put it back in loop () and keep timers for things like the UI (at much less than 8kHz of course).

I'm trying to calculate hf transformer core losses with the iGSE but I can't find the steinmetz coefficients for anything from any material or core datasheets. Where the fuck can I find them? I don't want to use charts since I want to stick the loss equation into a spreadsheet.

Also is there more to power input protection than fuses, movs, and thermistors? I don't like the thought of transient voltages frying expensive fets before the mov can react.

>>938130
>>938132
https://www.arduino.cc/en/Tutorial/SerialEvent

This looks pretty handy though. I might use this.

>>934047
Almost everything in that list is utter shit, and the only difference between them and the Cyberpower home shit is how much money they pay out if your equipment is damaged.

The actual tech behind these has improved dramatically, and gotten a hell of a lot cheaper. Ironically the mid teir hasn't changed much wine the more and high end have greatly improved. Now your only choices are cheap, or really really big. Like, comes with a story contact, and must be moved with a fork truck big.

>>938136
>>>934047
>comes with a support contact

>>936945
>video

Why is he saying that EEPROM can only be programmed once?

>>938157
he's australian. it's already a small miracle that he gets things right more than half the time.

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>>938157
>made me listen to that faggot
No idea why he says E^2PROM, but the chips in question were EPROM-based. Without window they're one time programmable.

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I posted this a few threads ago after I got the simulation in decent working order. I just finished assembling it and powered it up without a load and it has a nasty oscillation that doesn't appear in the simulation. it's about 100 mV peak to peak and roughly 130 kHz. The op amp output is pretty close to the negative rail, much closer than simulated. I'm thinking its bottoming out and bouncing or something, but I'm not quite sure what is causing it. The output sits around -8 V in the simulation. I double checked my wiring and resistor/capacitor values. Anyone have any insight? Real-life power supply is filtered but unregulated, with the exception of the op amp which is powered from a pair of lm7915/lm7815 chips.

>>938175
>nasty oscillation that doesn't appear in the simulation
Simulators are generally bad at simulating oscillators.

I'd start by removing the most compensation capacitors except C5 and by limiting that level shifter's gain by some bit more predictable way, like adding an emitter resistor for Q6.

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>>937914
>7805
>SMPS
read a book, PLEASE
captcha : 555

>>937270
BEEEEUTY

>>937914
IIRC there actually is a sample circuit for a switching supply in the datasheet for those voltage regulator chips.

>>938189
Thanks. Most of that mess of caps were added to keep the simulated circuit from oscillating, namely C6. If the simulator oscillates, should I assume it will be even worse in real life or should I assume that it's inaccurate?

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>>933576
So Im repairing my 3d printer which needed a new ramps 1.4, and a heated bed.

The heated bed is 12v @ 180w, so it should be 15 amps.

I directly soldered 16 awg wire to the ramps 1.4 board underneath the D8 terminals.
After about a minute, the mosfet sending the power to the heated bed starts smoking and continues to do so.

Seems to me that the mosfet is dissapting a lot of power because of of high RDS claimed to be .5 ohms by the people on this forum http://www.soliforum.com/topic/2080/magic-smoke-on-ramps/

What do you guys think?

(going to read about rds in AOE III now)

>>938231

power is I*I*R, or 15*15*0.5 which is 112watts of dissipation. that's crazy coz the IRF512 is only rated for 20W. i dont believe anyone would choose a FET with that high a series resistance for a high-power load. you need a device with something closer to 20 or 50 milliohms.

>>938212
Generally the sim is more well-behaved than the real thing. That would suggest your design has a fundamental issue.

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I'm going to make one of these clouds and I want to make something to sense lightning (probably rf) and make if flash at the same time, is such a thing possible?

>>938231
If the FET really is 0.5Ω then you'll have to replace it with a different one.

A quick google says that
http://www.digikey.com/product-detail/en/STP55NF06L/497-6742-5-ND/1039551
is recommended as part of the ramps spec. You can also find FETs in the 2-4mΩ range for the same price that might not even need a heatsink, but go with what's known.

>>933576
so i'm currently working on fixing/rebuilding an old stereo of mine that has a munted speaker. i've got two spare speakers that are the same size and fit perfectly, same wattage even, but the replacement speakers are 8ohm and the current speakers are 3.2ohm

is that going to be a problem at all?

>>938298
they will be quieter, but they won't blow up or anything.

>>938285
Yes.

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can't say what it is but does anyone know a good way to get or build a good interposer with microbump contacts?

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>>938305
hate using these probes.

>>938264
>>938296
>>938231

Thanks, ill order one of those.
Until that has arrived, could I decrease the wattage the heated bed consumes, with some arrangement of generic capacitors, resistors, diodes, and transistors? (what I have on hand)

>>938310
I don't know if ramps lets you manually limit the PWM duty cycle it uses to control the pad's temperature, but if it does you could set that to a low maximum value. Half an ohm is a lot of resistance in this context though so it's going to heat badly regardless.

>>938311
It does! As well as PID settings, and bang bang? on off?
I don't even know, much research to be done.

So 255 is 100% current flow with reference to what amperage? the 11amp fuse? what the bed is trying to draw? some other value?

>>938311
In my experience the Bed is usually bing-banged. Not PWMd.

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>>938332
>>938311
Forgot pic

>>938175
>2SA1943/2SC5200
Godly combination

>>938212
Yeah, I guessed so, but putting compensation capacitors everywhere isn't really the way to go. If you look at amplifiers designed by others, the compensation is frequently done with just one capacitor. If there are more, they tend to be there to compensate different things.
Your opamp is designed to be stable at unity gain, tolerating some reasonable amount of phase shift/delay. If you increase the total loop gain above the unity gain (R15/R16 attenuates less than your BJTs amplify), it's bound to oscillate. Similarly, if the BJT part is slow enough, your circuit is bound to oscillate.
Based on that, manageable and predictable gain would make your life easier. Same with speed, faster BJT part and slower opamp make things easier. And since the primary unhappy part is your opamp, moving compensation closer to it is likely to have better effect.

Simulated stuff tends to be more stable than real stuff, sometimes to the extent that intentional oscillators are slightly difficult to start.

And yes, you can build a switching regulator around 7805. Not that it was anon's intention.

>>938302
How would I go about it?

>avr is dead

Yeah no

>>938392
It is rather likely that Microchip will stop developing / eventually kill some product lines, but I'd expect Atmel's ARMs to go before AVRs. Atmel and Microchip also have some directly overlapping stuff like memories.

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>>938231
>(going to read about rds in AOE III now)
I needed a few seconds to realize you were not going to read about on state resistance in Age of Empires 3. I am not very smart

>>938403
Every time I see that abbreviation I think age of Empires. That's why I always use TAOE for the book

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>>938306
Looks like you have some sort of semiconductor devices (diode, polymer/perovskite solarcells?) on top of ITO/FTO glass.

The way you are characterizing them at the moment will be easiest to do. if you want something more robust you would need to redesign your sputter/evaporation mask to perhaps bring the rear contacts to a set of test pads (to make sure they don't short you would need to remove the FTO/ITO layer underneath them), then just use a set of spring loaded contacts (like the ones in pic).

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>>938421

they're often called pogo pins, and can be bought in singles or in arrays. usually they're placed as part of a kind of mold so that you can press the device under test into the mold, and the pogo pins align to the test points. the dude's gadget has a very irregular outline, so that strategy wont work.

>>938135
>>938132
I tried serialEvent () but it was a bit laggy. With the 8 kHz timer ISR there is no percievable lag but when I set up another timer to scan the UI (at a more modest 208.333 Hz) then it stops processing MIDI data.

In fact, it stops processing if there is anything at all in the ISR linked to this other, slower timer.

Any ideas why this would happen?

Has anyone here ever had a Cordless drill trigger open in a way that enabled you to put it back together?

I'm playing around with a scrap bin Alphatools Cordless drill.
The motor, battery and driving transistor all look to be in perfectly good condition, the trigger however is melted.

The melting point however seems to be under the actual moving parts of the trigger, since mechanically it operates as it should.

Just looking into perhaps fixing it, as long as it's not epoxy'd

>>938305
>>938306
Stop screwing with alien technology you know nothing about. Just give the aliens back their shit and apologizefor shooting them down before they wreck this world.

>>938529
just put in a new switch and fill any gaps with epoxy. function over form. what matters more, it being useful or it looking pretty?

also why do you name/tripfag everywhere you go?

>>938421
Where can i buy those? You know of a good site?
I need then with rounded ends like the ones in your pic but all i have are sharp pogo pins.

I want a whole square array of them with a ribbon cable coming out of them.

>>938683
I'm guessing this is for a uni project, if so your department (or definitely the electrical engineering one) would have an account with element14/DigiKey. Have a look here:
http://au.element14.com/webapp/wcs/stores/servlet/Search?catalogId=15001&langId=43&storeId=10184&categoryId=800000003858&st=spring%20loaded&pageSize=25&showResults=true
http://www.digikey.com.au/product-search/en/connectors-interconnects/contacts-spring-loaded-and-pressure/1442508?k=spring%20loaded

As for the ribbon, this is something you will have to do yourself, or maybe ask some one from electrical to do it for you.

Does anyone here have experience with measuring D.C. current using a non-invasive hall effect sensor?

Something like this:

https://www.sparkfun.com/products/8882

My project car is turning into one big electronics project and I would like to use several of these but I'm unsure of how accurate they are and if I would need to shield them at all from interference from the ignition coil.

So far I've replaced all the gauges with home made gauges, each powered by a 328P along with a 5v 15amp switchmode regulator under the hood.

Also considering adding audio and self-diagnostics just to see if I could do it.

Something along the lines of the radio cutting out and playing .wav or .ogg over the speakers to alert me to a blown fuse to start with.

Preferably using a voice synth similar to:

https://www.youtube.com/watch?v=NCmrp38KjYg

for shits and giggles

This is all pre OBD-II and more or less a big rolling proof of concept for shit I come up with, so any neat or gimmicky ideas are a go.

>>938705
How large is the current you want to measure, and to what accuracy?

For those of you who use arduinos, do you use genuine Arduino brand Arduino or copies?

I've used nothing but copies so far due to the price difference, but I've gotten a lot of duds lately that kind of make me want to shell out money for the real thing.

Also, is it hard to get money back for non-functioning copy boards through eBay? I bought 2 boards from a seller but one came dead on arrival, but they said they wanted to help me fix it first (even though I've tried burning the bootloader back onto it many times now).

>>938760

Preferably +/- 0.5A, 0.25 to 0.5 resolution would be plenty.

Maximum current for each device would probably be 30 amps at max, as I can't see the point in including the starter motor. Pretty obvious when that isn't working.

>>938794
Righto, you could try and getting the 30A variant of the ACS712 to see hot it goes, they are super cheap on ebay.

>>938377
Look up how to make a lightning detector. If you want to be cheap about it, you can use an AM radio. During a lightning storm, the bottom band of AM between stations will pick up lightning as static crashes. You could use the static signal to control the lights. Otherwise you could do it digitally by reading from your local weather station which usually logs lightning strikes, if you don't mind connecting it to the Internet.

>>938908
I think I'll play around with an AM radio, seems like there'd be a lot less latency and I don't think my town's big enough to log lightning strikes.

>>938792
I got given a legit one and I've had no problems with it. Running on average an hour a day.

I have a quick question.
I had a broken laptop screen, bvacklight was still working though.
I want to reuse the leds from it. How do i calculate how much volts and ampers i need to give it to work ?

>>938983
Trial and error

>>938986
I thought so too. But i didn't saw inverter in there so this is some lower voltage ? below 20v ?

>>938474
So nobody knows why, on an architecture with 3 timers, I appear to only be able to use one in practice?

>>938792
I've got two legit ones, and probably close to a dozen knockoffs I've gotten for different projects.

Problems I've heard about but never experienced: bad power circuit, bad capacitors, no/incorrect resistor on LED causing it to blow. Not one of those problems, ever

Problems I have had: low quality silkscreen, unlabeled pins, mislabeled pins, cheap connectors that have to be bent beech into place.

>>939144
I bought a DCCduino on eBay for about £4, then about a week later I saw a genuine one with a case and a load of components and nice gizmos, breadboard, etc for £15.

So now I have 2. Funnily enough, the genuine one only works on one of my PCs (it doesn't even register as a USB device), while the clone works perfectly.

>>939144
>>939149
Oh, I almost forgot, the TX and RX LEDs are the wrong way around.

I'm thinking of building an SMPS bench supply. All the schematics I've seen have 600-650v fets chopping the rectified mains. Is that high of a voltage rating really necessary? Even euro mains is 350v peak and all the input protection and rfi filtering should hopefully dampen any 200v transient spikes before they reach the fets. Seems like a huge derating like that is terribly cost and rds-on inefficient.

>>939400
When it comes to mains voltage levels, I think the extra safety is worth it.