24 to 12 volt circuits

Thread Starter

MI Installs

Joined Jul 26, 2007
2
Installing equipment on off road machinery that is 24 volts. I would like to get my power source from the ignition switch. The device only draws 50mA @ full power (12 Volts) and I have a limited amount of space to work with.:confused:
 

SgtWookie

Joined Jul 17, 2007
22,210
For 50 mA @ 12V you just might be able to use a 7812 in a TO-220 package. At 600 mW it will get just a bit warm.
That should work OK - but you should also use some capacitors on the input and output to prevent oscillations, because it's a given that the wire length is going to be at least a foot either way. Use an 0.33 uF cap to ground on the input, and a 0.1 uF cap to ground on the output, both with a 30v rating. Otherwise, the oscillations could lead to some mighty high voltage spikes.

A Texas Instruments uA7812C has a rated output of up to 1.5A (with proper heat sinking, of course) with a minimum Vin of 14.5 and max Vin of 30. If you get it too warm, it'll let you know by shutting down (thermal overload protection). A National LM7812 or other xx7812 would work just the same.
 
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