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Author Topic: Review Arduino Board Design  (Read 2729 times)
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What do you have going on with buttons? Why do you have VCC going out to them?
I would change to only have GND & the pin connected, place to add 10K pullup to VCC if the internal pullup is not enough. Then test for a low to see if button is pushed.

That pulldown & button shorting to VCC is just bad news - wish the tutorials did not teach that.

FTDI connector looks funny - if you want to plug on an FTDI basic for example, the pins are gnd-gnd-vcc-rx-tx-dtr. Guess you're just missing a gnd.

You show +5V on the input to the regulator - should +7V.
Connect the cap on the other side of the diode.
Add another 0.1uF cap to either pin 7.
Since you have room - move the reset switch & cap down a little, add holes for a header to the ADC pins, just in case. Can be used as digital pins also.

The board:
The VCC Sel header is labelled FTDI. Rotate it 180 also.
Put a +7V near the positive pin of the EXT connector so you know.
Add a label near JP1 and JP2.

Have you figured out polygon?
Delete all your ground traces.
Add a polygon to both layers. Name them GND. Click Rats Nest and let eagle connect all the grounded pins to the polygons.

You could optionally make the traces wider also, for better durability & resistance to ham-fisted soldering for example.

Overall: Nice job for a first time with eagle & pcb design.
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Hey crossRoads quick question, i dont know if you etch pcbs at home or not, but if you do how do you go about preventing them from oxidizing ?
I have some boards ive made for various projects and they look like crap after a week or so ... i was thinking buy some enamel spry paint and throw that on there since it prevents rusting ...?
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Wow, eddiea6987 and CrossRoads,

  Thanks for all your help!  I'll work on "v2" of the schematic and board later today or tomorrow and upload it when complete.

RE: The buttons - really I should have labelled them different.  On this one project I am doing, they are buttons, but I want to be able to reuse this board for other things, so I was thinking "if I send 5v, gnd, and a digital pin out as a three-point plug, I can plug any sort of contraption into them later".  But realistically, I think your idea is much better: just use them for what they are.  Also, I didn't remember that the digital pins had an internal pull-up resistor, so I will be changing them to pullups as suggested.

Thanks again!
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I don't etch at home.
There is stuff liquid tin you can pour on the boards as the last step that should do what you want.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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I have some boards ive made for various projects and they look like crap after a week or so ... i was thinking buy some enamel spry paint and throw that on there since it prevents rusting ...?

I haven't tried a DIY PCB yet, but a while back I was reading some tutorials on it. Some of them talked about a spray-on compound, maybe lacquer. Just found this tutorial on tinning.

http://eegeek.net/electronics/tutorials/tinnittutorial.htm

Lady Ada also talks about tinning. http://www.ladyada.net/library/pcb/inhouseetch.html

This sounds like something I've read before: http://rockgrotto.proboards.com/index.cgi?board=m&action=print&thread=2901
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When I was an apprentice we always painted PCBs with a thin coat of solder-through lacquer, shortly after etching and cleaning. From memory, the lacquer had some slight flux properties, and definitely didn't make soldering any harder.
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In the process control industry it's common to have PCBs treated with 'conformal coating' due to the possibility of H2S contamination. This is a fairly thick epoxy painted over the whole board including all components. It really makes repairing such boards more complex, but it does certainly protect the board from corrosive atmosphere.

Lefty
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I use clear nail varnish

let me re-phrase that  smiley-eek
I paint clear nail varnich on etched PCBs
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I've used normal matte lacquer before and it worked like a champ!  I'm not too sure what the electrical insulation it provides, but after 8 months the traces are as bright and shiny as the day I etched it.

I applied multiple light coats on the freshly etched board and let it dry for a few hours.  The heat (and flux!) from the soldering iron is enough to clean the lacquer off the pads, so it will act as a sort of solder mask as well.
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alrighty then thanks fellas i think ill try both the nail varnish and matte lacquer , aside from the fact you have a board in minutes etching etching, at least the way i do it, can get more expensive then ordering  pcbs online :/
freaking  presensitized boards from parts express cost an arm and a leg for the sizes they offer, i am thinking of trying out the "negative" photoresist film rolls they have on  ebay which dollar for dollar i will get a lot more boards from a roll of that stuff with all the regular copper clads  i have lying around
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Have you tried the laser transfer method?
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Do a little reading before proceeding much further:
http://www.delorie.com/pcb/liquidtin/
http://www.circuitspecialists.com/421-125ml.html
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Okay, here's V2 - hopefully with all the feedback incorporated correctly.  The ground plane things was much easier than I anticipated.  Eagle really isn't that scary after you kind of figure out how they like to do things (doing some AutoCAD in the past is a big help since they act similarly).

I dumped the Molex connectors I had in favor of regular breakaway pins since the buttons no longer depend on polarity.

* plugduino-v2-schematic.pdf (33.59 KB - downloaded 10 times.)
* plugduino-v2-board.pdf (79.92 KB - downloaded 15 times.)
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I'm not seeing the traces for the 0.1uF decoupling caps on pins 7, 20, 21. Check on those.
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Okay, here's V2 - hopefully with all the feedback incorporated correctly.  The ground plane things was much easier than I anticipated.  Eagle really isn't that scary after you kind of figure out how they like to do things (doing some AutoCAD in the past is a big help since they act similarly).

I dumped the Molex connectors I had in favor of regular breakaway pins since the buttons no longer depend on polarity.
I would recommend that you wire up both halves of the reset switch.  This increases reliability and could prevent a problem later on.
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@CrossRoads,

  I think that they're there, but maybe I have them incorrect the auto-route did the routing, so some things are kind of goofy.  For instance, the trace from pin 20 to the cap goes on top to a resistor solder pad, then drops to the bottom for the rest of the route.  I've attached a few printoffs of the different layers of traces with and without the polygon filled.  Let me know what you think.  Maybe I am not doing it right.

@JoeO - I will probably do that on the next edit before sending it in.  I'm rushed this morning.

Thanks!

* plugduino-v2-board-no-polygon-fill.pdf (68.32 KB - downloaded 13 times.)
* plugduino-v2-board-top-filled.pdf (49.52 KB - downloaded 6 times.)
* plugduino-v2-board-bottom-filled.pdf (48.82 KB - downloaded 8 times.)
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