voltage reducer formula

what is the formula for reducing a 12 source(battery) to run a 9 volt device. i know i need to also install a voltage regulator.

What are you connecting and is it a constant current draw? The formula is E=IxR (voltage = current x resistance) if the current changes, the resistance required changes also. If it's something simple like a light, it will be easy to figure out. You need to know the current draw or the wattage. If it's something like a portable CD player, go to Radio Shack and buy a converter..it will be easier.HotRod

thanks hotrod! thats what ill do!

yea you dont really want to use any voltage divider setup although you can if you know the current draw of the load. A linear voltage regulator can be used, it may get hot so i recommend a heatsink, you can also use a zener diode, i think 9.1 V is a standard value zener...

thanks xetmes, what im want to do is, use a 12 volt batt to power 6 or 9 volt loads for prolong times. maybe 6 hours or more. and i wanted the extra useage from the 12 source. that way by the time the voltage starts to drop and effect the loads ability to perform  its proper function, i would be done for the day. and recharge if needed the battery for the next days fun! thanks for your help! it should be easy to make and probly it is already ava. at radio shack if id get up and look for it!

hmm the problem with using zener diodes and voltage regulators in applications like this is they waste power, thats why they get  hot.. I though this was going to be put in a vehicle where the wasted power is not really a big deal.. If you want a more effiecient way you could oscillate the 12V and step it down and rectify it, but for just 3 volts it would not be worth it... so i guess your best bet is still a voltage regulator or zener.. dont ask me why i typed this hah

yeah defenetly what he said everything stolen :(

Workin on a new system :)

Peace in the middle east