Quote Originally Posted by No1_sonuk View Post
<noob mode> What's the laser for? </noob mode>

Better to use 2 diodes in series - they can give a different voltage drop dependent on current flow.

If you don't need to run the laser for a long duration (assuming it's for alignment of some kind) the batteries/relay idea is safer.
It is for setting the zero work coordinates. Useful on a router where absolute precision isn't needed (cutting a sign maybe). If I need precision, I use a touch probe.

Well, I've got a 5v regulated PSU and a relay board so I'll try your suggestion of the two diodes (100 just arrived from the Bay :) )

Thank you everyone for the help.

Jeff.