This circuit above can drive 25 small Xmas lights. The lights operate at about 200mA and 3 volts. The supply voltage is set to 5 volts and the 4017 counter output will drop about a volt using the 2N3053 transistors. The voltage on the emitters of the rows transistors will be about 0.7 volts less than the base so the lamp voltage will be about 3 volts. You can adjust the supply voltage for the desired current if necessary. It works the same way as the LED version but you need diodes in series with each light. Most any small diode rated at 500mA or more should work. I used 1N4001 diodes. Various NPN transistors can be used, I tried 2N2219A and 2N3053. The 2N3053 worked out better with a higher gain than the 2N2219A, but either one should work.

Copyright 2006 Bill Bowden

1x 555 Timer IC
2x 4017 decade counters
Misc NPN transistors, condensators, resistors, etc.