Help regarding voltage regulators.

[jjotjjotjjot]

Hi! I'm currently having problems with my voltage regulator circuit. My input voltage is 42V. My first voltage regulator steps down input 42V into about to 12V, I then paralleled a L7805CV that uses the 12V as its input to have an output of 5 volts. I used the output of the L7805CV as an input to a LM317 voltage regulator. The problem is that when I measure the output at the LM317, I only get about 0.5-0.54V when I configured it to have an output voltage of 3.3v. can anyone please help me? Thanks.

 

[dougy83]

Have you got it wired correctly? Note that the LM317 has a different pinout to the 7805 & 7812.

 

[colin55]

LM317 needs about 3v across it. Try jacking up the output of the L7805CV. Or make the input of the LM317 12v.