Electrical Engineering V2 - Developers

So I've got this audio amp that's being fed by an atmega audio player and outputting to a loudspeaker, and it just doesn't seem that loud. I'm wondering if it's because I'm sending it a DC signal instead of an AC audio wave, which the amp chip's datasheet says it takes. Would adding a cap to my audio line help out?

Finally ran out of parts. Will have to hold off for another month or so again. Installed an Auxiliary Relay. Somply when the teletype is switched to LINE mode it closes this relay and will allow 120v to flow to a convenience outlet mounted in the stand. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8093.jpg[/IMG] Also reassembled everything to see my progress. All the rewiring inside the teletype should be somewhere close to finished. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8096.jpg[/IMG]

Chryseus and Ddrl46 ganged up on me and told me to stop dragging my ass and just cut and mount the PCB. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8099.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8100.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8101.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8102.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8103.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8105.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8107.jpg[/IMG] Had to drill an extra hole so I could reach a screw underneath. The phone bracket slips between two washers and then you poke a screwdriver through the hole to tighten it down. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8109.jpg[/IMG] The mounted board does not have a lot of vertical clearance near the front however has plenty os room near the back. The idea is to keep the microcontroller, transistors and all the wiring connections on that and then put the relays on one or two pluggable PCB's. Parts to do that are now on order. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8117.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_8120.jpg[/IMG] I also forgot to add the extra wire that the microcontroller uses to inject RS-232 data into the loop adapter. I will have to do that some other time.

These kind of connectors: [t]http://i.imgur.com/W9NBQO9.png[/t] do they have a specific name? I've never really used proper connectors like that before in projects, and it wouldn't hurt using them. For example a 4 pin version would be handy for I2C connections

Molex? Also wow are APRS beacons ever cheap to make. Hook up a [URL=http://m.ebay.com/itm/191210888951]DRA818V[/URL] in the same way you would an ESP8266 and you're off to the races! Time to 3D print a weather station.

So uh what's the easiest way to take mains to 3.3 that saves on space?

[QUOTE=POLOPOZOZO;47064356]So uh what's the easiest way to take mains to 3.3 that saves on space?[/QUOTE] Find an old wall-wart that puts out 5V+, gut it, put in an adjustable regulator that's tuned to 3.3V. Or, depending on what you're doing, you could try to find a wall-wart that puts out 3V, assuming your circuit can operate on those voltages (what's .3V between friends anyway?).

[QUOTE=Cakebatyr;47063933]Molex? Also wow are APRS beacons ever cheap to make. Hook up a [URL=http://m.ebay.com/itm/191210888951]DRA818V[/URL] in the same way you would an ESP8266 and you're off to the races! Time to 3D print a weather station.[/QUOTE] Heh, I'm currently working on implementing APRS for a High Altitude Balloon, and the specifications are utter shit. The only thing APRS has going for itself is the wide coverage.

[QUOTE=Zero-Point;47064423]Find an old wall-wart that puts out 5V+, gut it, put in an adjustable regulator that's tuned to 3.3V. Or, depending on what you're doing, you could try to find a wall-wart that puts out 3V, assuming your circuit can operate on those voltages (what's .3V between friends anyway?).[/QUOTE] That's what I thought but I need the 120 in the box, too. [editline]3rd February 2015[/editline] also i was wrong I need just 5

[QUOTE=POLOPOZOZO;47067686]That's what I thought but I need the 120 in the box, too. [editline]3rd February 2015[/editline] also i was wrong I need just 5[/QUOTE] Depending on your current requirements, find an old wall-wart for a cell-phone. They usually put out 5V and are pretty small depending on who makes them, and will be smaller still if you remove the plastic shell.

Problem: So I've given up on my RS-232 Tx injection because thigns are not playing nice with the mark/space thing, instead I'm trying to inject data into the TTL input of the MAX232 between it and the 4200 series optocoupler so I only need one MAX232 and I don't have to worry about reverse voltage signalling. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/untitled-2.png[/IMG] Problem: With just the diodes attached the data becomes garbled and bits randomly flip. What gives?

[QUOTE=pentium;47072293]Problem: So I've given up on my RS-232 Tx injection because thigns are not playing nice with the mark/space thing, instead I'm trying to inject data into the TTL input of the MAX232 between it and the 4200 series optocoupler so I only need one MAX232 and I don't have to worry about reverse voltage signalling. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/untitled-2.png[/IMG] Problem: With just the diodes attached the data becomes garbled and bits randomly flip. What gives?[/QUOTE] It's possible that the forward drop of the diodes is causing the HIGH logic voltage to drop below the threshold for logical high in the chip which is why you're getting undefined behavior.

So, this is going to be fun... All 21 GHz of it. [url=http://i.imgur.com/sJZuand.jpg][img]http://i.imgur.com/sJZuandl.jpg[/img][/url]

[QUOTE=Dolton;47073553]It's possible that the forward drop of the diodes is causing the HIGH logic voltage to drop below the threshold for logical high in the chip which is why you're getting undefined behavior.[/QUOTE] I sent ddrl46 a waveform and noted that after the diodes the fall from 5v to 0v had a slope during a state change. He recommended a 10K pulldown resistor and that solved the problem.

[QUOTE=ddrl46;47073898]So, this is going to be fun... All 21 GHz of it. [url=http://i.imgur.com/sJZuand.jpg][img]http://i.imgur.com/sJZuandl.jpg[/img][/url][/QUOTE] Twenty one gigahertz?

[QUOTE=Fourier;47074910]Twenty one gigahertz?[/QUOTE] Yes, 21 jiggawatts... I mean gigahertz.

Right, I painted myself into a corner. So as we we proceeded on from the problem above I realized I can't mix the signals. It doesn't matter which input is being used because both inputs normally sit at 5v and drop to 0v when triggered. It only takes one of the two inputs sitting idle (5V) to cancel out the second input (can't go low when something is forcing the line high). Assuming we use NOT gates... [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/1-2.png[/IMG] ...then of course remembering that the MAX232 needs that 5v input, so we invert the signals again... [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/1a.png[/IMG] It still wouldn't work because now the signal ends up stuck being pulled low by either input at idle, thus causing your re-inverted output to be stuck high. Wandering into uncharted territory again. In my mind it's impossible to fix.

That would be the point where I'd just throw in an atTiny but I'm sure smarter people have smarter solutions.

Nah, put an IGBT in there.

Why not use CMOS logic ICs? Doing this stuff with discrete transistors seems unnecessary.

I don't know what kind of logic to use. To me I don't care if both devices possibly transmit at once and garble the data (because it's unlikely to happen and if it does I can repeat the command). I just need both inputs to go into one data line.

[QUOTE=pentium;47077742]I don't know what kind of logic to use. To me I don't care if both devices possibly transmit at once and garble the data (because it's unlikely to happen and if it does I can repeat the command). I just need both inputs to go into one data line.[/QUOTE] Quickly drew something up for you: [t]http://a.pomf.se/kxnmds.jpg[/t] Basically I wrote down a truthtable, and then recognized that it's basically an AND, which can easily be built with 2 NANDs. Some NAND ICs only cost a few cents and will do the job, just make sure they're 5V compatible.

What would you guys suggest for powering something with a max of 3.6 amps @ 5 volts? I've got a strip of 60 WS2812 LED's, and I considered powering them from an Arduino nano's 5V pin but I can't see that going well in any way with them drawing that much. Thinking about it, I don't know many things capable of supplying that. [editline]6th February 2015[/editline] There are plenty of high current supplies out there I notice actually. Only issue I have now is that I don't want to have seperate sources (as the nano runs on a minimum of 7V, and the LED's preferrably on 5)

Bypass the regulator on the nano and you can run it all on 5V.

A spare ATX supply or potentially a high current iPad charger?

The 5V rail on an ATX PSU has fairly good regulation, in my limited experience. A spare ATX supply would work nicely.

I shouldn't have butchered all the spare power supplies just for their fans 2 days ago :v:

[QUOTE=scratch (nl);47087507]I shouldn't have butchered all the spare power supplies just for their fans 2 days ago :v:[/QUOTE] Given your requirements and the size of most PSU heat sinks, you should be fine with passive cooling.

Cooling is for pussies. Also, [url="http://i.imgur.com/ChRMdse.jpg"]I have an idea...[/url] I need a smaller keyboard, and maybe upgrade to a Pi 2.

[QUOTE=LoneWolf_Recon;47087626]Given your requirements and the size of most PSU heat sinks, you should be fine with passive cooling.[/QUOTE] I didn't really remove the fan with tlc :v: I actually spared one PSU, but it might be one that broke as it got taken out of an old computer for a good reason probably, and the fan doesn't start when plugging it in (and turning it on) [editline]6th February 2015[/editline] what would be a good way of checking it? measuring current?