How do I use a 12V power source for a 1.5 volt bulb? I don't want to buy another power source, especially when most of my lights run on the 12V source I have. I would like to get some 1.5 volt minibulbs, but I know it'll fry the bulbs. What resistor do I need, or is this even an option?
Well you could just buy 8 bulbs and light them all together... or use a resistor. Argh, my brain can't remember the exact resistor to use. been a while since electronics class.
To use only a resistor you need to have an idea of how much current the bulb is going to draw, then it can be easily calculated. Jeff
Your best bet is to use a 1.5 volt regulator connected to the 12v source. It will make lots of 1.5v power available for many bulbs. No resistor is required. Radio Shack doesn't stock these, but they do have the LM317T adjustable regulator. It makes 1.2 volts in the simplest arrangement and that will run your 1.5 volt bulbs with a longer life but good brightness. If you feel it necessary, a couple of resistors will adjust the voltage to exactly 1.5 volts. You'll also need the appropriate heat sink and the total cost should be about $5. It comes with instructions. Ray
The other way you could do it would be a diode and a resistor. You'd get about 1.4V across the diode, the resistor gets to drop the rest. The resistor needs to be a small enough value to not limit the current through the bulb, but large enough to limit the current through the diode, or at least keep it from being ridiculous. A regulator would be a cleaner way, if you have room. Jeff
Ok guys, before I go to Radio Shack, I've got a couple of questions. How exactly does this wire up? And what do you mean by heat sink, and how do I install it? Electronics isn't my thing, although I've learned a lot more since I've gotten back into trains that I did before hand.
