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.

Bill of Materials

Qty	Description	Manufacturer's Part Number	Farnell Order Code	RS Order Code
1	ATmega8 Microcontroller	Atmel ATMEGA8-16PU	917-1380
1	28-pin DIL Socket	Multicomp 2227MC-28-03-05-F1	110-3850
1	16MHz Crystal, HC49/S	IQD LF A161K	971-3700
2	22pf ceramic capacitor	Multicomp 2222 680 34229	113-8845
3	100nf ceramic capacitor	Multicomp MCRR25104X7RK0050	121-6438
1	10nf ceramic capacitor
1	6-way 0.1-inch Header	Harting 09 18 506 7324	109-6984
1	2-pin KK Header	Molex 22-27-2021	973-1148
1	Rectangular amber LED
1	390Ω resistor
1	10kΩ resistor
1	Pushbutton switch