"Intermediate" tutorial on PCB layout?

Community PCB Design
6

Dave, thanks for the offer. At the very least, getting help routing this board will teach me some general lessons.

I don’t have the EAGLE files handy on this PC but I do have this screen capture of one of my routing attempts:

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http://i2.photobucket.com/albums/y30/de … roller.gif

The circuit has a few main areas:

  1. Lower left-center is power. There’s an SMT +5v regulator for main power, plus a voltage inverter and -5v regulator. This raises a question - when I’ve got several regulators close together like this, how do I determine the caps needed for each one?

  2. Immediately above and to the left of the power section is a real time clock (DS1307). This bit is simple and I’ve used a similar circuit many times before, but never on the same PCB as all this other stuff.

  3. Top left is a stripped-down “Arduino.” There’s the processor and resonator, plus some resistors and an FTDI header.

  4. The big IC towards the top right is a port expander to drive an LCD (header for the LCD is the long one far top right). The LCD header will be on the bottom of the board, allowing this PCB to be plugged in to the back of an LCD. Also up in that corner, a 2x6 header to provide two ports each for I2C and One Wire. Almost all of the external circuits/devices I’ll be using with this controller will be I2C or One Wire. Just below the 2x6 header is a 12mm buzzer to provide an audible alarm.

  5. The big mess in the bottom right, taking up all the room covered by the top ground plane is an amplifier circuit for a pH probe. I lifted this circuit off another hobbyist. It works on it’s own, but it’s never been put on a busy PCB like this. Do I need a separate ground plane for this big (mainly analog) section? Do I use one big ground plane on the bottom, plus separate ones on top (as I have it now) or just separate ground planes on one side only?

  6. Also evident are “standard” Arduino headers, to allow shields to be stacked on this PCB as if it was a Duemilanove. And one last lonely 3 pin header, just to the end of the LCD header, to bring out one of the digital pins with a power and GND pin for a sensor I’ll be using that’s not One-Wire compatible.

So, like I hinted in my OP above, I’ve got some digital areas, some analog areas, some sensitive crystals, plus a bunch of awkward tracks to route to the “standard” Arduino headers, which add a lot of mess. In the attempt I posted above, I had tried to route some of those traces manually, then let the autorouter finish, which made a huge mess around the resonator.

Thoughts, suggestions, helpful wishes appreciated. . .