Electrical Engineering V3 - Developers

[media]https://www.youtube.com/watch?v=xLUf2ymoltQ[/media] Yay for coil guns.

[t]http://i.imgur.com/WAaqvJS.png[/t] Can someone remind me why it is that it is a good idea to hold the PIC in reset for a short period of time? I've forgotten, and my book isn't being much of a help

[QUOTE=gokiyono;52157327][t]http://i.imgur.com/WAaqvJS.png[/t] Can someone remind me why it is that it is a good idea to hold the PIC in reset for a short period of time? I've forgotten, and my book isn't being much of a help[/QUOTE] Probably something to do with bootloader passing so that instead of waiting for the ISP to load new firmware it just goes directly into the application code. AVRs do something similar but most of the circuitry is built in and all that is required is to pull down the RESET pin.

[QUOTE=gokiyono;52157327][t]http://i.imgur.com/WAaqvJS.png[/t] Can someone remind me why it is that it is a good idea to hold the PIC in reset for a short period of time? I've forgotten, and my book isn't being much of a help[/QUOTE] Really the best thing to do with PICs is to switch to AVRs or some cortex m0 of your choice (for example STM32)

Are there any EE graduates who'd be willing to take a questionnaire about their job? It's a really long one but it make it worth your while I'll gift you a game of your choice (up to 50 bucks) on steam. I can go more in depth through PM if anyone is interested.

[QUOTE=DrDevil;52161239]Really the best thing to do with PICs is to switch to AVRs or some cortex m0 of your choice (for example STM32)[/QUOTE] Can't agree more. So much more community contributions and if you have a board that supports mbed, developing for it is an ease, not to mention a lot of free compiler suites.

So I just built [URL="https://www.banggood.com/DIY-TDA7294-100W-Subwoofer-Amplifier-Board-Kit-p-989281.html?rmmds=myorder"]this[/URL] cheap amp board for a tactile trancducer (I don't really care for audio quality here) and only now noticed that it either needs AC Dual 11V ~ 25V or ± 35V DC neither of which I have a power supply for Now I have two laptop power supplies just laying around here, one being 19V 4.47A and the other being 16V 4.5A. After some reading online it seems that I could build a +/- supply by connecting them up a certain way Will that cause any problems because of the voltage mismatch? Also will I need to add a (or maybe I need two?) regulator for it?

Hunt down the power brick for one of the many Lexmark printers in the late 90's and the 00's. I know they used a 35v DC power brick.

Only ones I can find on ebay are like <1amp, I think I'd need more like 3-4 amps. Also I doubt these are +/- supplies

[QUOTE=LennyPenny;52168508]Only ones I can find on ebay are like <1amp, I think I'd need more like 3-4 amps. Also I doubt these are +/- supplies[/QUOTE] The TDA7294 does require a dual rail supply. The circuit board is designed to provide this for you, if you use the AC input, 11V to 25V rms, otherwise you will need a dual DC supply. If you want more than a few watts out you must mount the TDA7294 on a heatsink or it'll melt down, also you will not get even close to 100W with that simplified design, maybe 20W or more with a substantial heatsink. Also laptops supplies will most likely be no good, with 30dB of gain and the probably poor PSRR the noise will likely swamp your input signal.

Okay yea I'm retarded I just need a transformer, I'm guessing any cheap ass tranformer from ebay that does 220v to 20v will do? And yea I already ordered the heat sink with it, it will only have a to drive a 8ohm 50wrms tactile transducer so I couldn't really care less about probably even 15% distortion :v:

[QUOTE=LennyPenny;52169058]Okay yea I'm retarded I just need a transformer, I'm guessing any cheap ass tranformer from ebay that does 220v to 20v will do? And yea I already ordered the heat sink with it, it will only have a to drive a 8ohm 50wrms tactile transducer so I couldn't really care less about probably even 15% distortion :v:[/QUOTE] Yep that should do fine, a rating of 50VA would be sufficient for your application.

Woooow these are pretty expensive [editline]30th April 2017[/editline] Also the description says something about "dual" AC Is that something special?

[QUOTE=LennyPenny;52169154]Woooow these are pretty expensive [editline]30th April 2017[/editline] Also the description says something about "dual" AC Is that something special?[/QUOTE] After taking a closer look at the PCB it needs a transformer with a center tap, these are usually sold as two separate windings. Something like this is suitable: [url]http://de.farnell.com/pro-power/ctfc50-24/transformator-50va-2-x-24v/dp/1780860[/url] You wire it up like this: [img]http://i.imgur.com/qmJNXuy.png[/img]

Turns out farnell only ships to business customers in germany, uuuugh

[QUOTE=DrDevil;52161239]Really the best thing to do with PICs is to switch to AVRs or some cortex m0 of your choice (for example STM32)[/QUOTE] Unfortunately, out teacher insists us using a PIC16, which sucks. I at one point looked up a problem I had, where I found someone with the same problem as I, and the answer was basically "get with the times grandpa" :v:

[QUOTE=LennyPenny;52169303]Turns out farnell only ships to business customers in germany, uuuugh[/QUOTE] That sucks, try look for a local supplier, you can get some pretty good deals on transformers if you shop around.

[QUOTE=Chryseus;52169462]That sucks, try look for a local supplier, you can get some pretty good deals on transformers if you shop around.[/QUOTE] Okay last time bothering you as don't want to get this wrong Is either of these ok? [url]http://www.ebay.de/itm/Netz-Transformator-Trafo-Pr-230V-Sek-2-x-19V-49-4VA-5420-/311838750832?hash=item489b09b870:g:hVMAAOSwdGFY4WXt[/url] [url]http://www.ebay.de/itm/Universal-Netztransformator-2-x-230-V-2-x-20-V-AC-80-VA-2-A-IZ-67-elma-TT-/361194099743?hash=item5418d8941f:g:IRwAAOSwstxVMFRX[/url] I really want the first one to work as I want to spend as little money was possible

[QUOTE=LennyPenny;52169303]Turns out farnell only ships to business customers in germany, uuuugh[/QUOTE] And students. Write to their customer support.

[QUOTE=LennyPenny;52169601]Okay last time bothering you as don't want to get this wrong Is either of these ok? [url]http://www.ebay.de/itm/Netz-Transformator-Trafo-Pr-230V-Sek-2-x-19V-49-4VA-5420-/311838750832?hash=item489b09b870:g:hVMAAOSwdGFY4WXt[/url] [url]http://www.ebay.de/itm/Universal-Netztransformator-2-x-230-V-2-x-20-V-AC-80-VA-2-A-IZ-67-elma-TT-/361194099743?hash=item5418d8941f:g:IRwAAOSwstxVMFRX[/url] I really want the first one to work as I want to spend as little money was possible[/QUOTE] Both of those are fine.

Okay I got the thing now [t]https://vgy.me/F2GFCL.jpg[/t] I'd connect my power line up to 1 and 6 right? (I'm on 220v) Is there convention as to what is coming out my wall is 0v and whats 220v? [editline]5th May 2017[/editline] Oh wow that little thing on the left most side even is earth

[QUOTE=LennyPenny;52189954]Okay I got the thing now [t]https://vgy.me/F2GFCL.jpg[/t] I'd connect my power line up to 1 and 6 right? (I'm on 220v) Is there convention as to what is coming out my wall is 0v and whats 220v? [editline]5th May 2017[/editline] Oh wow that little thing on the left most side even is earth[/QUOTE] 1 and 6 yes, if the output voltage is lower than you want you can try 1 and 7, in Germany and most of Europe the nominal supply voltage is 230V so either can be used, it isn't critical. You generally don't need to earth transformers, it's more for convenience since insulation faults on transformers are exceedingly rare, if you mount it to a metal chassis then it should be used.

Anyone have a good methodology for organizing parts? I'm finally building up my own workbench and went ahead and started organizing parts in excel. I'm using x4 of [URL="https://www.harborfreight.com/40-bin-organizer-with-full-length-drawer-94375.html"]these organizers[/URL] for passives (1 Res SMD, 1 Res TH, 1 Cap & Ind SMD, 1 Cap & Ind TH) and then x1 of [URL="https://www.amazon.com/Akro-Mils-10144-20-Inch-16-Inch-Hardware/dp/B003P2UOCO/ref=pd_lpo_469_bs_t_2?_encoding=UTF8&psc=1&refRID=WDV1WKXBM6JJ9055C5P2"]this organizer[/URL] for ICs & Active Discretes (Both SMD & TH). So far this is how I have it organized: [img_thumb]http://i.imgur.com/VNGvdMi.png[/img_thumb] [img_thumb]http://i.imgur.com/jphk6qJ.png[/img_thumb] [img_thumb]http://i.imgur.com/a9UH3QG.png[/img_thumb] And a rendering of what I have so far for the workbench (yellow boxes are the organizers, and then the rest is a bench supply, Rigol Scope & sewing machine), I'll probably be mounting pegboard to the back beams of the bench too: [img_thumb]http://i.imgur.com/I8eoEbZ.png[/img_thumb]

Parts organizers are good, I also use things likes these: [t]http://i.imgur.com/SXSzcLg.jpg[/t] Salvaged stuff I usually just throw in a box or metal biscuit tins, plastic takeaway boxes are also very useful as well if you don't mind your parts smelling like old chinese food.

FLIR cameras are awesome for troubleshooting. [img]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/board_overview.jpg[/img] [img]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/romram.jpg.jpg[/img]

What system are you diagnosing?

CBM PET. Yes, THAT Commodore computer. [img]http://cdnaka.dcfever.com/articles/news/2015/07/150716_commodorepet_02.jpg[/img] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/Computer%20related/IMG_5830.jpg[/IMG] It's one of the early models that use unobtanium MPS 6550 DRAM and ROM that likes to go bad. All the chips run hot in comparison to today's IC's but when they do fail they become visibly hotter under a thermal imaging camera due to internal short circuiting. I can see at least three ROMs are looking funny.

Are the ROMs in industry/IEC standard pinouts? I'd almost see if you could burn the ROMs on more modern EPROMs to save on power/heat/etc.

The early PET uses the MPS 6540 mask ROM it is not pin compatible with EPROMs. You need to build [url=http://www.dasarodesigns.com/product/mps-6540-commodore-pet-2001-rom-adapter-obsolete-rev-3-version/]this adapter[/url] to be able to use 2716 chips. Unfortunately it is a component that requires PCB's to be fabbed. So I cannot assemble them in my workshop without placing an order.

[QUOTE=pentium;52217433]The early PET uses the MPS 6540 mask ROM it is not pin compatible with EPROMs. You need to build [url=http://www.dasarodesigns.com/product/mps-6540-commodore-pet-2001-rom-adapter-obsolete-rev-3-version/]this adapter[/url] to be able to use 2716 chips. Unfortunately it is a component that requires PCB's to be fabbed. So I cannot assemble them in my workshop without placing an order.[/QUOTE] You like hacky stuff, just get a laser printer and do the toner-transfer method.