ATmega8 Prototyping PCB

• Make the PCB with Toner Transfer
• Use an Atmel AVR chip, the ATmega8
• Enough room for a ULN2803 darlington driver chip (18-pin DIL)
• Use up a spare piece of copper-clad board I've had since the 1970s
• Maximise the usefulness of the PCB for breadboarding/prototyping
• Enough room for two 16-pin DIL chips in addition to AVR chip
• Enough room to expand I/O pins of AVR with shift registers, muxes, etc.
• Six-pin programming header, but with polarisation keyway
• Reset button
• PCB tracks wide enough for easy toner transfer
• PCB layout for four TO220 power transistors or MOSFETs
• Power-on LED
• Minimise area of copper etched away, to make ferric chloride last longer
• Stick to business card or ISO credit card size
• Ground track all around outside edges
• Use free and open source tools, e.g. GNU PCB

More photos of the PCB and the etching process are in this Flickr set.