Melanie, That does sound like a clever way of doing it but i think it might be a little over complicated. Using a single pin would be essential. If i can only have 11 bulbs per board then i need more than 7 boards and to address them correctly i need more than 4 DIP switches (taking up more inputs or using multiplexing). You said that i could use 1 pin but that would add even more components to the board. I understand roughly how your diagram works but im not too sure about the resistor. Last time i used a resistor in series with these bulbs i ended up with a fire. The zener probably takes care of that though (aswell as protecting the chip).

Acetronics, That sounds like a good idea. Its like the ammeter version but replacing the resistor/opamp/adc programming with a simple reed switch. Doing it this way instead of the way in my PCB layout means theres no relay so that transistor can be used to drive another bulb. I should probably do some testing first though to see if a single bulb can draw enough current to get a magnetig field strong enough. www.donsbulbs.com says that the smallest bulbs i have are 0.15A. Should that be "10-15 turns divided by amps"?

About the transistors. I used to use some ULN chips which i think were rated at 500mA but im not sure if thats per output or per all 8 outputs. Im sure there was a good reason i changed to transistors but i cant remember what it was. I always prefered the ULN chips. The transistors do seem to be more expensive but i suppose i dont have to have them in groups of 8. I know at first i had some ULNs soldered into PCBs and ended up blowing them up. Eventually i started putting DIL sockets in (should have done this from the start)