Electrical Engineering V2 - Developers

I'm a big supporter of the John Madden Communications Protocol. Example with 3 hosts: [img]http://i.imgur.com/AnekwFE.png[/img]

I was aware that 555s where cheap but holy crap 50 for <$2 is really cheap!

Guys, I've got my little PA amp all working now, but it causes massive amounts of EMI to my car radio as well as my ham radio. It's enclosed in one of those fancy extruded aluminum boxes, so I don't think it's radiated EMI. I was guessing it was noise being fed back to the car's power line through the power wire. How do I fix this? A lowpass on the ground wire, or something else? I tried clamping a ferrite core to the power wire, and it only helped very slightly.

[QUOTE=papkee;46493941]Guys, I've got my little PA amp all working now, but it causes massive amounts of EMI to my car radio as well as my ham radio. It's enclosed in one of those fancy extruded aluminum boxes, so I don't think it's radiated EMI. I was guessing it was noise being fed back to the car's power line through the power wire. How do I fix this? A lowpass on the ground wire, or something else? I tried clamping a ferrite core to the power wire, and it only helped very slightly.[/QUOTE] Show us the circuit diagram.

[QUOTE=alexaz;46496094]Show us the circuit diagram.[/QUOTE] [t]http://i.gyazo.com/e99e9e90b26ba5ea91e5a30142d24c39.png[/t] This is all inside an aluminum case. I didn't assemble much besides the atmega's board, and that's just a 16mhz crystal and some caps. Everything else I just ordered from ebay because it was a lot cheaper than buying parts and getting my own pcb's made.

[QUOTE=Cakebatyr;46493738]I was aware that 555s where cheap but holy crap 50 for <$2 is really cheap![/QUOTE] Do you have a link?

[QUOTE=papkee;46496314][t]http://i.gyazo.com/e99e9e90b26ba5ea91e5a30142d24c39.png[/t] This is all inside an aluminum case. I didn't assemble much besides the atmega's board, and that's just a 16mhz crystal and some caps. Everything else I just ordered from ebay because it was a lot cheaper than buying parts and getting my own pcb's made.[/QUOTE] Well, the first suspect for noise would be the DC-DC converter. If its a cheap switching one from China then try looking for the datasheet of the chip on the board and look for what components were left out to keep the cost down. There's a reason why Chinese boards with chip and all the passives cost less than a single chip from TI/national semi.

Papkee, what is the program you use for that circuit? I've been searching for a good program, instead of using the clusterfuck that fritzing is.

Looks like EAGLE.

So I'm trying to print something on my printer, and all of a sudden it says OH GOD A JAM HELP ME. So i open the back and I find an opto-sensor from a printer that I took apart previously.... Wow, revenge from the grave?

[QUOTE=scratch (nl);46496845]Papkee, what is the program you use for that circuit? I've been searching for a good program, instead of using the clusterfuck that fritzing is.[/QUOTE] I use EAGLE, but there is also KiCAD.

I got my Panasonic NCR18650B batteries from an eBay seller finally. 2-3 weeks late and the seller got banned a short while after I bought the batteries. But I've been giving them some use now. I don't have any real equipment to properly assess them, but I believe them to be the real McCoy. Damn good batteries. I recommend. Makes me want to have the option of battery-powering my power supply design. After looking at all the cheap Chinese LM2596 super-small single-board things, that just have a few parts and they work nicely, makes me want to functionality to my idea, otherwise I'm just basically doing what apparently half of China has already done.

[QUOTE=alexaz;46496440]Well, the first suspect for noise would be the DC-DC converter. If its a cheap switching one from China then try looking for the datasheet of the chip on the board and look for what components were left out to keep the cost down. There's a reason why Chinese boards with chip and all the passives cost less than a single chip from TI/national semi.[/QUOTE] It's the small 12v-5v one from [URL="http://www.current-logic.com/dcdc_converter_car.php"]this company[/URL]. They obviously want to give you absolutely no information about the internal circuitry, so I'm just going to go ahead and put in some filter caps anyway and see if that helps.

I watched some more eevblog videos, and I got far enough back that I ran into videos where he's making a lab power supply. Didn't even know those videos existed. And then I saw the finished package, and he had the idea of having the possibility of making it battery-powered. Monkey see, monkey do. Now I totally have to do that. Also, I decided the laptop charger I was thinking about, could do the job if I don't ask much of it, but it's a bit wimpy. And I cracked open the case on an old Nokia wall wart that pukes out 5V 350mA, it looks fairly simple. I really need to decide on a spec. 12V max output voltage at 1A would serve me fine, but argh, I could do so much more than that. How do I know when I'm adding too much crap into something?

[QUOTE=nikomo;46506414]I watched some more eevblog videos, and I got far enough back that I ran into videos where he's making a lab power supply. Didn't even know those videos existed. And then I saw the finished package, and he had the idea of having the possibility of making it battery-powered. Monkey see, monkey do. Now I totally have to do that. Also, I decided the laptop charger I was thinking about, could do the job if I don't ask much of it, but it's a bit wimpy. And I cracked open the case on an old Nokia wall wart that pukes out 5V 350mA, it looks fairly simple. I really need to decide on a spec. 12V max output voltage at 1A would serve me fine, but argh, I could do so much more than that. How do I know when I'm adding too much crap into something?[/QUOTE] Using a laptop charger or a similar switching supply will negate all the benefits of a linear design since these are practically always high noise supplies, in that case you'd be better off making a switching regulator for it. If you're going with a linear design then 1A, maybe 2A is your limit without one of those fancy transformers with multiple taps, otherwise power dissipation starts to get a bit ridiculous, you could use a combination switching regulator and linear regulator but then you start to lose the advantages of a linear design, assuming you're using a proper mains transformer. Also this arrived on my desk today, Christmas has come early! [t]http://u.cubeupload.com/Chryseus/3ev3g4.jpg[/t] [t]http://u.cubeupload.com/Chryseus/I7siqi.jpg[/t] :dance:

I gave the autorouter a try. Ahahahahahahaha. No. Also, here's my current thing's schematic: [t]http://i.imgur.com/aNKBxKy.png[/t] [QUOTE=Chryseus;46511035] If you're going with a linear design then 1A, maybe 2A is your limit without one of those fancy transformers with multiple taps, otherwise power dissipation starts to get a bit ridiculous, you could use a combination switching regulator and linear regulator but then you start to lose the advantages of a linear design, assuming you're using a proper mains transformer. [/QUOTE] My current idea is to have a boost for the batteries, and have that adjustable. You give microcontroller that you want 12V out, boost adjusts to 13-14V output, then it goes to a linear regulator to have a nice, smooth output. Big heatsink on it, 1A output max, thought I think I could maybe go for 2A, but I don't think I need that much. Dave Jones' design uses the 1A version of... I think LM3080.

Autorouters are a good tool if used properly. Autorouters only work as good as you place the components. They can give you a valuable starting point that might require some manual optimizations. They obviously only work for uncritical signal lines.

That little adapter broke my wire wrap tool. :( Time to buy a new one that's not plastic this time. [img]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_7266.jpg[/img]

Any potential pitfalls in buying those cheap Chinese Arduino clone things on eBay? Also, made a PCB today, tried doing a "silkscreen", ended up being fairly bad, but at least it's something, and at least I tried. Also tried to tin up a bitmap image of Rosetta I left on the board, didn't go too well. Ton of flux around it, need to clean it out when I get to school tomorrow. [t]http://i.imgur.com/b9x0YK4.jpg[/t] [t]http://i.imgur.com/wBmdehl.jpg[/t]

When you tin such a huge surface, you need an iron with enough power to heat up the entire heat reservoir.

I'm still using the stupid stock tiny conical tip that came with the iron. My tips were supposed to arrive on Monday, still nothing. Also, I love the middle finger. I might just start including that into everything.

I've always wanted to try my hand at homemade PCBs but I never quite understood how you get from printing transparencies to chemical etching. I'm not entirely sure how you protect the traces.

had my first class of camera image processing (using python and USB webcams), and I'm so hyped for it now and got a great excuse to get a raspberry pi as it'd be fucking perfect for things like that (assuming it can process image data at a good speed?)

[QUOTE=Cakebatyr;46520014]I've always wanted to try my hand at homemade PCBs but I never quite understood how you get from printing transparencies to chemical etching. I'm not entirely sure how you protect the traces.[/QUOTE] It depends upon the process; in general, transparencies make it easier to align the printed design (Using toner, not ink printers) onto the bare copper and then heat up the toner to then transfer to the copper. The transferred toner then protects the covered copper from the etchant as toner is rather resistant to etchant. If you want to try it by hand, sharpies/expo markers are a crude but workable way to draw out your traces. (Albeit it takes some more scrubbing after etching).

Mains AC is giving me a headache. The electricity here in Finland is simple. 230V, 50Hz, and you can plug it in either way. But apparently the Brits have something different, and you have a live and a neutral, and you have to actually care how you connect it. It's giving me a headache, because I was thinking I want to just have an IEC 320 C14 power socket thing, but I have no idea if I have to specially care how to rectify that etc. if someone took the design, built it in the UK and used it over there.

[QUOTE=LoneWolf_Recon;46520546]It depends upon the process; in general, transparencies make it easier to align the printed design (Using toner, not ink printers) onto the bare copper and then heat up the toner to then transfer to the copper. The transferred toner then protects the covered copper from the etchant as toner is rather resistant to etchant. If you want to try it by hand, sharpies/expo markers are a crude but workable way to draw out your traces. (Albeit it takes some more scrubbing after etching).[/QUOTE] If its that simple I may invest in a hot plate... Could start reflow soldering with one too now that I think about it.

[t]http://u.cubeupload.com/Chryseus/ThxY1c.png[/t] Discrete voltage regulator with current limit. Because I fucking love transistors.

[QUOTE=Cakebatyr;46520967]If its that simple I may invest in a hot plate... Could start reflow soldering with one too now that I think about it.[/QUOTE] Ink transfer is inferior to photo-etching. You get a pre-sensitized board, place a transparency sheet with a pattern on it, blast it with a UV lamp ( could be LEDs, too ), dip the thing a developer solution. I'v gotten boards with 0.2mm traces.

do they sell board ready for photo etching at electronics stores often? It'd be interesting to try.

[QUOTE=nikomo;46520839]Mains AC is giving me a headache. The electricity here in Finland is simple. 230V, 50Hz, and you can plug it in either way. But apparently the Brits have something different, and you have a live and a neutral, and you have to actually care how you connect it. It's giving me a headache, because I was thinking I want to just have an IEC 320 C14 power socket thing, but I have no idea if I have to specially care how to rectify that etc. if someone took the design, built it in the UK and used it over there.[/QUOTE] Pretty sure yours is identical - you just don't have a ground pin. The only reason we have a "live" and "neutral" is because the live is one phase of a 3 phase system and the neutral is the common neutral point. I can't see off the top of my head how connecting it backwards would make any difference - it would still be a 50 HZ 230V sine wave.