On 07/15/2016 06:35 AM, Bruce Esquibel wrote:
Cursitor Doom wrote:

When connected to an external bench power supply at 12V., the board draws
9.3mA. The bench PSU doesn't have any issues powering this board.

When connected to PSU that uses the LM317, however, it draws 3mA and the
voltage across it drops to around 6V.

If the current requirements are that low, why don't you use something like
the LM7812 instead of the 317?

They are far simpler to use, aren't as flakey as the 317 and about as cheap.

Unless the supply the 317 is in is needed to be voltage adjustable or
high current (or higher than a LM78xx can produce), you'll save a lot of
hair pulling using the LM7812.

-bruce



What's flaky about the 317? You can blow them up by overvoltage, or by
pushing a large current backwards into the ADJ or output terminals, but
otherwise they're pretty well-behaved. Well, they will oscillate if
you're running at low gain and you put 10 nF on the output. However,
it's a 1-A class regulator, and just about any circuit needing anything
like that much juice will have a lot more capacitance than that.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net