Circuit Board Design

[colin]

Hey guys, I just need somebody to verify my circuit board design to make sure everything will work properly! I've looked it over and it all looks fine but I don't want to pay the $150 to get some panels created and THEN recognize an error like I did last time!

Im looking for things like:

- design advice
- ground pour
- vias
- spacing

[2k1Toaster]

So it is just a breakout board for analouge ins and digital outs?

Not sure if it is just an image artifact, but the top layer's bottom edge silkscreen doesn't line up.

[Curiosity]

I don't see any errors. Hope that's a cap or 2 on Vusb.

[JS8531]

Probably the most professional designed PCB I have seen in this forum so far.

[colin]

Quote: Originally Posted by 2k1Toaster

So it is just a breakout board for analouge ins and digital outs?

Not sure if it is just an image artifact, but the top layer's bottom edge silkscreen doesn't line up.

The board is my version of your "Fusion Brain". It is USB controlled, has 14x 500mA outputs from the ULN2003, has 2x PWM outputs, 14 In/Out/Analog, etc. I'm using it to control all my stuff -- it's a project I revamped from about 2 years ago, maybe 3. It all started from the Car I/O project on this very forum, thanks to Curiosity.

Yeah it's a tiny bit off at the bottom but there's a gap on the ACTUAL parts so its there to line it all up once assembled. I'll look into it, thanks.

Quote: Originally Posted by Curiosity

I don't see any errors. Hope that's a cap or 2 on Vusb.

That's 2 caps, 100nF each. According to the data sheet, "An
external 220 nF (±20%) capacitor is required for stability." I did that because my SMD collection only has 100nF caps, most of them are in the pF range.

Quote: Originally Posted by JS8531

Probably the most professional designed PCB I have seen in this forum so far.

Thank you Took me quite a while to get it right! Last time I ordered an older version of this PCB and it didn't have a ground plane and the switch was connected wrong. It never did work. I'm hoping this time I won't mess up right off the bat.

[Curiosity]

Oh! I forgot about that project. hehe.

I probably would swap the USB jack and LEDs or put them in some odd spot, but your design gives it a nice look.

The one thing I skipped was the ULN2803. Are they going to be switching 5V? Why not 12V?

[colin]

Quote: Originally Posted by Curiosity

Oh! I forgot about that project. hehe.

I probably would swap the USB jack and LEDs or put them in some odd spot, but your design gives it a nice look.

The one thing I skipped was the ULN2803. Are they going to be switching 5V? Why not 12V?

Why would you swap the LEDs or the USB jack? And where would you put them?

The ULNs will be switching 5v, but they only switch ground so technically they could switch a 12v system too as long as it shares the same ground. The reason it's switching 5v is because I have a ton of 5v relays from eBay that I would ideally like to use. Also, this will be powered off a USB hub and a molex connector. I would rather it used one supply to keep things simple. This way I can use a simple 12v to 5v POL regulator and run a USB hub AND this board together at the front of the car without a molex.

[Curiosity]

Oh I was thinking that would just be straight for the USB. LEDs would then fit on the right side.

The reset button: I'm pretty sure it should be tied directly to the MCLR pin to pull all the way to ground. It shouldn't cause any problems with the porgrammer plugged in either.

[colin]

Quote: Originally Posted by Curiosity

Oh I was thinking that would just be straight for the USB. LEDs would then fit on the right side.

The reset button: I'm pretty sure it should be tied directly to the MCLR pin to pull all the way to ground. It shouldn't cause any problems with the porgrammer plugged in either.

Sorry, I really don't know what you're talking about with USB

As far as reset goes, that's how I usually did it. Except this circuit is to be programmed with the PICKIT2 programmer that I got knocked-off from eBay. In the user manual, it says to put a 470ohm isolation resistor before the button, which I did. The other resistor is just a pull-up to VCC to ensure that MCLR doesn't get a floating input.

The problem lies with the programmer being plugged in AND the button being pressed (perhaps accidentally). Would you really want 13v shorting directly to ground? I wouldn't.

[colin]

Revision 1.2:

+ Added thermal planes on the bottom layer for the chips which could get hot
+ Added silkscreen:
+ 1 PWM Ports
+ 2 Interrupt Ports
+ 3 Barcode
+ 4 Identification + Logo