Electrical Engineering V3 - Developers

[QUOTE=Goz3rr;51969609]I've got a 9V AC/DC Chinese adapter that I can't open and am wondering what's inside. I've tried using a mains detection screwdriver on the output (didn't light up) Measured the voltage between ground (earth on the wall socket) and output, was 9V Measured resistance (while unplugged obviously) between input and output pins, seems to be infinite I'm pretty sure this means it at least has a transformer in there (and not a capacitive dropper). I'm not too concerned about it blowing up because I'll only use it when present, more about getting shocked from accidentally touching something connected to it (i.e arduino) because it's at mains potential[/QUOTE] If its one of those blocky wall warts, usually you can just crack em open a the seams with a vise, hammer and flat edge screwdriver. Usually any transformer based converter is isolated well enough from mains but I've seen some shitty exceptions: [video=youtube;T88ej64aXUM]http://www.youtube.com/watch?v=T88ej64aXUM[/video]

So I have this old RadioShack analog multimeter that my friend gave me awhile ago, and it doesn't seem to be working when I try to measure the voltage on a small battery. I'm not really sure where to start in trying to fix this thing but here's the internals: [T]http://i.imgur.com/CluVGbM.jpg[/T] (Yes, I had a battery inside when I was measuring, I just took it out)

[QUOTE=thefreemann;51975359]So I have this old RadioShack analog multimeter that my friend gave me awhile ago, and it doesn't seem to be working when I try to measure the voltage on a small battery. I'm not really sure where to start in trying to fix this thing but here's the internals: [T]http://i.imgur.com/CluVGbM.jpg[/T] (Yes, I had a battery inside when I was measuring, I just took it out)[/QUOTE] Check the meter movement isn't burned out, the fuse and the connection to the input jacks is fine. Battery is normally only used for resistance measurement.

[QUOTE=Chryseus;51975605]Check the meter movement isn't burned out, the fuse and the connection to the input jacks is fine. Battery is normally only used for resistance measurement.[/QUOTE] Hmm ok, I took some of the screws out to remove the board, but it looks like something is soldered in the upper right hand corner near the red wheel, I guess I'm going to have to break it if I wanna get in?

[QUOTE=thefreemann;51975697]Hmm ok, I took some of the screws out to remove the board, but it looks like something is soldered in the upper right hand corner near the red wheel, I guess I'm going to have to break it if I wanna get in?[/QUOTE] Looks like a pot, desolder it and it should lift off, I see what looks like a screw in the hole below it, maybe try remove that first.

[QUOTE=Chryseus;51975788]Looks like a pot, desolder it and it should lift off, I see what looks like a screw in the hole below it, maybe try remove that first.[/QUOTE] I removed that screw and the others, so it looks like I'll have to desolder. I've only soldered a little bit, and never figure out how to desolder. I tried using one of those things that sucks the solder up but it wasn't working too well, any tips for that?

[QUOTE=thefreemann;51976765]I removed that screw and the others, so it looks like I'll have to desolder. I've only soldered a little bit, and never figure out how to desolder. I tried using one of those things that sucks the solder up but it wasn't working too well, any tips for that?[/QUOTE] Push it down as best as you can to get a decent seal, they're not really that great when it comes to larger connections, tight fitting pins or odd shaped holes, solder wick is pretty much the best in this situation. Alternatively you could bridge the three pads with more solder so you can heat the lot and pull it off, you'll need to clean off the old solder with a solder pump or preferably wick before reinstalling.

[t]http://i.imgur.com/HX9gNSn.jpg[/t] Holy shit that's a huge capacitor

Let me find a picture from my summer internship. One sec... [editline]18th March 2017[/editline] [t]http://i.imgur.com/EyQU44P.jpg[/t] We used four.

What kind of internship was that? Building coilguns or something? :v:

Aww, they're so petite! [t]http://i.imgur.com/NC514gF.jpg[/t] But them tolerances though... :v:

(unrelated to my multimeter) If you happen to be working with some device's innards, is it advisable to first discharge any capacitors? Because even if you unplug the device or turn it off, the capacitors can still hold charge right?

[QUOTE=thefreemann;51988599](unrelated to my multimeter) If you happen to be working with some device's innards, is it advisable to first discharge any capacitors? Because even if you unplug the device or turn it off, the capacitors can still hold charge right?[/QUOTE] Yes, especially if its HV (>50V) or AC line capacitors.

AC line filtering capacitors are a pain in the ass (or hand), I have a drill that remains charged for ages after using it so I have to short the plug out on something before I put it away, not exactly dangerous but certainly painful.

I have a 10W 100 ohm resistor I simply put across the terminals on large line capacitors. It takes a few seconds and on the larger caps the resistor does get warm but it does a great job rendering them safe to handle. [editline]asdas[/editline] So last weekend I stole the Molex connector off a photocopier and made a new ECU diagnostic port that is hidden under the passenger side glove box. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_7432.jpg[/IMG] Now lets kick the hornets nest and see how the Rhinoman enjoys eating his own words. :evil: [url]http://www.suzuki-forums.com/general-suzuki-non-model-specific-discussion/53109-aldl-serial-interfacing-3.html#post1352817[/url]

Speaking of discharging capacitors, I was working on a plasma TV and decided to discharge the 600V capacitors on the power supply board using a knife. Needless to say, the sparks were pretty and the bang was loud :v:

[QUOTE=supervoltage;51990974]Speaking of discharging capacitors, I was working on a plasma TV and decided to discharge the 600V capacitors on the power supply board using a knife. Needless to say, the sparks were pretty and the bang was loud :v:[/QUOTE] My HVAC instructor had a tip for discharging capacitors in AC units: Use Craftsmen screwdrivers. [I]Specifically[/I] Craftsmen. Why? Because when they get too fucked up, you could walk in to Sear's, ask for a replacement, and they had to give one to you. At one point someone told him "Y'know, I'm not supposed to ask, but what in the hell are you doing with these?" to which he replied "You're right, you're not supposed to ask. :) " [editline]21st March 2017[/editline] [QUOTE=pentium;51990181] Now lets kick the hornets nest and see how the Rhinoman enjoys eating his own words. :evil: [url]http://www.suzuki-forums.com/general-suzuki-non-model-specific-discussion/53109-aldl-serial-interfacing-3.html#post1352817[/url][/QUOTE] Thread's closed, but honestly at this point you seem to be just as petty as he is.

[QUOTE=Zero-Point;51991910] Thread's closed, but honestly at this point you seem to be just as petty as he is.[/QUOTE] I don't think I've ever run into someone who sells ECU monitoring software who wasn't a massive cunt. Also it seems the moderator snipped the end of the post before closing it. Fuck them.

[QUOTE=pentium;51993100]I don't think I've ever run into someone who sells ECU monitoring software who wasn't a massive cunt. Also it seems the moderator snipped the end of the post before closing it. Fuck them.[/QUOTE] Best way to beat assholes like them is to make and sell your own thing at a lower price. I have a big issue with people selling vintage service info at ridiculously inflated prices, so instead I get hold of it one way or another and sell it myself for a fraction of the cost, I love how angry they get but they have no legal standing to stop me.

Something I'd like to point out to those who aren't aware; if you need cheap, quality, high power (>1kw) 12V power supplies, just buy old server gear! Check it: [url]http://www.ebay.ca/sch/Network-Server-Power-Supplies/56090/bn_886981/i.html[/url] There are a few models such as the HP DPS-1200 which seem to have a cult following among the RC Car community for use with high current battery chargers. Many other models are/were used by Bitcoin miners so there's a good chance you can find the pinout to turn them on online.

hi anyone want to help me figure out what the heque this signal is [img]https://dl.dropboxusercontent.com/u/5168294/screencaps/Screenshot%202017-03-23%2020.41.56.png[/img] and how i could replicate it while being able to change the frequency of it easily? thx

Looks like an abs(sin(x)) But where did you dig that up

i am obligated to not divulge that information at this time but i think we managed to make it? at least, i think so [img]https://dl.dropboxusercontent.com/u/5168294/screencaps/photo_2017-03-23_23-07-46.jpg[/img]

Try abs(sin(2π*f))^a where a is something like 0.1.

I dunno looks more like a standard square wave/PWM with just a high duty cycle. (And maybe some RC or LC loading on it).

Really hard to say when the signal is so undersampled... Can't you change the timebase of whatever is displaying it?

it's not my signal tho i'm planning on measuring it myself with a higher resolution, i just don't have access to it yet

Anyone here have experience with those serial driven relay banks? [t]http://g02.a.alicdn.com/kf/HTB14DUkPXXXXXcxXXXXq6xXFXXXb/221872405/HTB14DUkPXXXXXcxXXXXq6xXFXXXb.jpg[/t] How much rocket science goes into the signalling protocol of the no-name chinese built units?

[QUOTE=pentium;52007276]Anyone here have experience with those serial driven relay banks? [t]http://g02.a.alicdn.com/kf/HTB14DUkPXXXXXcxXXXXq6xXFXXXb/221872405/HTB14DUkPXXXXXcxXXXXq6xXFXXXb.jpg[/t] How much rocket science goes into the signalling protocol of the no-name chinese built units?[/QUOTE] You probably just push a single byte over serial to it to set the states

[QUOTE=pentium;52007276]Anyone here have experience with those serial driven relay banks? [t]http://g02.a.alicdn.com/kf/HTB14DUkPXXXXXcxXXXXq6xXFXXXb/221872405/HTB14DUkPXXXXXcxXXXXq6xXFXXXb.jpg[/t] How much rocket science goes into the signalling protocol of the no-name chinese built units?[/QUOTE] Yeah as DrDevil said, just a shift register driving a bunch of MOSFETs. [URL="https://facepunch.com/showthread.php?t=1452809&p=51884460&viewfull=1#post51884460"]We addressed it and solved it pretty well a couple pages ago.[/URL]