12v to 7.2v ??

[woodymaxx]

Hello I have a rig that uses a 12v for power and I am adding something that runs on 7.2 volts. How would I get the 12 volts down to around 7.2? Resistors? a potentiometer? I have tryed some resitors I use for my leds and they did nothing. So is it a potentiometer I would use? And if so how do I wire all that up. the potentiometers seem to have three prongs to solder to. how does that work? thanks a lot!!

[SandManRacing]

It all depends on how much current the device that use 7.2v will drain.

To use the correct resistor, R = V/I

R= Value of resistor in Ohm
V= Voltage across the resistor (12v-7.2v = 4.8v)
I= Current thru the resistor (or thru the device that will use 7.2v)

To know the correct power of the resistor (Watts)

W = VxI or I²xR or V²/R


Or the best choice would be to use a Voltage Regulator.
Very simple and cheap device that plugs between the power source and the load.

See :
http://www.national.com/pf/LM/LM317.html

Under 1$

Available at any electronic parts store. Even Radio-Shack...

[woodymaxx]

really at radio shack? whats the part number I work there! lol

[woodymaxx]

is this it? http://www.radioshack.com/product/index.jsp?productId=2062601&cp=&origkw=Voltage+Regulator&kw=voltage+regulator&parentPage=search how do you wire that up and adjust it?

[SandManRacing]

Yep that's the part you want :)

You will need to add some resistors to make it work.

http://www.national.com/pf/LM/LM317.html

R1 would be 240 ohm

R2 would be 1.2 Kohm (1200 ohm)

Resistors are ¼ Watt

Bye !

[SandManRacing]

The resistors will "adjust" the regulator to give you 1.2v output.

This part can provide constant 1.5A current. You can add a power transistor in parallel to boost the current to wathever you want.

You can look at a power supply I made to give you an idea.

http://70.83.160.67:85/images/circuits/powersupply2.gif

bye