LM317 regulater

[MrWild]

I'm making a control box for a G540 with a Keling 48v supply. One of the things I want to do is run a couple of solid state relays for the router and shop vac. These would be controlled through the G540. The relays I have are 3-32v DC control for 120v AC 10a. I'd really like to save some room (and learn something) and looking into voltage regulation, found the LM317 might be perfect. I say might be because I've never used the circuit before.

The 1.5a they are supposed to be able to push is way overkill. I'll only need 60-70ma at the most (20mz each relay plus some LEDs). What happens with the circuit when there is no load? Will the voltage rise and be too high when the circuit is closed? Should I include a load reisister?

Thanks

[vger]

The 317 will do fine with no load. Here is a link to the datasheet http://cache.national.com/ds/LM/LM117.pdf There is a limit on the input to output voltage difference of 40 volts so with 48 volts in you will have to set the output to greater than 8 volts. Don't forget the bypass capacitors from the input pin to ground and the output to ground, these things have high enough gain they will oscillate at a high frequency without the capacitors.