Tiny AVR rat's nest type circuit I thought it might be neat to have a one square centimetre micro PCB. At first glance this looks more like one square inch but that is only if you keep the optional extras.
Most if not all of the 8pin tiny series should work on this board. I have both DIP and SOIC footprints so either can be used or the board could be use and a SOIC to DIP breakout.
The circuit just has the basics. The micro doesn't need anything but a DC power source to operate. I've added a regulator, caps, power LED and another LED on an I/O pin. The LEDs have current limitings resistors.
The current version of the PCB is 0.9 inches square with spare pads filling the space. Not obvious in the image is the polygon ground plane fill on both sides.
To make a 1 cm^2 board simply cut off the surrounds. The regulator and I/O led a within the area taken by the DIP. The input filter cap is slightly outside this space. The circuit would probably work without this cap depending on the power source used. The 10uF output cap is overkill and it might be possible to mount both caps in the middle if smaller footprints are used.
I've ordered 10 PCBs (revision-b) so I don't expect to be making a rev-c in the foreseeable future.
Apart from the known short circuit they worked fine. Curiously if I power the micro directly from the USB programmer something smokes (rework flux fumes) but the micro boots and everything is cool by the time I can get at the circuit. The regulator is the only thing it could be.
All three boards I made do this. When powered from 12 volts (into the reg) they seem to work perfectly.
The other minor glitch is the holes in the prototyping area are too small to take normal headers (fixed on rev-c).
One LED didn't work and it appeared to be a faulty via (THP). I had to lift the "large" cap and fill the via with solder - then it worked. Also I didn't have 1206 sized tantalums so I used a 100nF ceramic.
Rev-c and rev-d used the smaller cap. Rev-d has a proto-typing area attached.
in this file http://nerdipedia.com/tiki-download_file.php?fileId=100
You can also order these PCB at BatchPCB.
Note these are the batchPCB prices - I don't make a cent from the sale.
small mega328 pcb