Hi, i am trying to step down 12v to 3.3v. I have two different 3.3v regulators i have tried (1.5a and 3a) and all i ever get out according to my voltmeter is 0.01v. I have tried a 5v reg and it works fine. Whats going on?
The part numbers are LM1085IT-3.3 and LM1086CT-3.3

 

Are you wiring them the correct way?, regulators often have different connections. I'm presuming you also have the required capacitors on the input and output?, instability could stop it working.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

They are the correct way round. The supply is a 12v lead acid battery and i have a 47uF cap between ground and +3.3v

 

As I see it there are only two possibilities?, either it's wired incorrectly, or you have faulty components somewhere - possibly both chips are faulty? (which seems highly unlikely). Another possibility is an external component, the 47uF S/C would probably cause this as would anything S/C on the output.

Is the chip mounted on a heatsink?, if so, is it insulated from the heatsink?.

It's a simple enough circuit, there's not many possibilities.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Damn you guys are right, its wired wrong :roll: I assumed it would be the same as the 5v ones.
Will i have killed it now?

Edit: Its alive and kicking thanks guys!