Resistor Question

Cherokee Kid, I'm going to be a typical Australian here and not give you the answer, what I will give you though is a hint on how to work out it yourself....

Using several equations of Ohms Law, it will give you the correct value of the resisotr required.....

Sorry, but it's something you need to work out for yourself.

Raymond Wilkinson-Reed

And I, being a typical American, will say I agree with the Ausie answer above that you need to understand the theory for yourself, but it never hurts to have a shortcut:

http://ourworld.compuserve.com/homepages/Bill_Bowden/r2.htm

 Using Ohm's Law, you can find the resistance..

 Volts equals Amps times Resistance

  If you want to drop from 12 volts to 9 volts, you'll be dropping 3 volts. If you know the current draw of your device you can figure resistance. Assuming 500mA current draw, your resistance would be 3 volts divided by 500mA.. the answer would be 6 ohms.

 Depending on what you want to do, you'd probably be better off using a voltage regulator.. describe what it is you're trying to do.

 Jim

One bleeder resister in series with a zener diode rated at 9v in parallel with your load will give you what you need.  Go to Radio Shack, tell them what you're doing, what you need, and they'll walk you through the rest.  The resistor you use will need to safely handle the current draw of the piece of equipment you're trying to power.