24 to 12 volt circuits

Discussion in 'General Electronics Chat' started by MI Installs, Jul 26, 2007.

  1. MI Installs

    Thread Starter New Member

    Jul 26, 2007
    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:
  2. Papabravo


    Feb 24, 2006
    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.
  3. SgtWookie


    Jul 17, 2007
    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.
  4. MI Installs

    Thread Starter New Member

    Jul 26, 2007
    Thanks for the responses

    Would it be possible to get a drawing of this circuit?
  5. John Luciani

    AAC Fanatic!

    Apr 3, 2007
    There are drawings in the LM7812 datasheet.

    (* jcl *)