CNC Relay Board

We’re having a thermal problem in an underwater housing for a pulsed laser system at work. It turns out the problem is that heat isn’t adequately being pulled away from the laser and the TEC eventually goes into thermal runaway. The quick solution is to switch the main laser power off when it’s not being used but there weren’t any relays to switch the power so I knew it was time for a new home-brew relay board.

I have a fairly complete electronics lab at home and one of my coolest toys is my little desktop CNC that I use to make quick turn PCBs. So lets get to it!

We bought some nice Omron G6RL-1 24V relays for the job so I slapped them and other components I had in my parts bin down on a quick schematic. We need to switch three power lines so we duplicate the same schematic 3 times.

Next step is to do a quick layout on a single side because we’re going to use some simple singled-sided copper clad board. We want the board to be fairly small as we don’t have too much spare room in the housing.

You can see in the next two images that I’m using some left over single-sided copper clad from a previous project. We’ll mount the relays and connectors on the unclad side and the SMT components in the bottom side.

I converted the gerber files to G-code using pcb2gcode so we can use EMC2 to mill the board.

Next we mill the board. The pointy bit with the blue depth setter is used to actually mill the isolation tracks that make up the circuit. The pink drill bit (0.037″) with the pink depth setter is used to drill the holes for the connectors. and the end mill bit with the red depth setter in the machine is used to cut the board out of the copper clad.

Here we tin the PCB to make soldering easier and to protect the copper from corroding. I’m using some left over tinning solution that I’ve had for a while. Not the freshest solution but it’ll get the job done.

We then flush and dry the tinned PCB.

Here’s the PCB under the microscope. The isolation tracks aren’t perfect but it’s good enough for my purposes.

Alright, let’s gather the parts…

…and get to soldering!

And here is the finished board! It needs to be cleaned a bit and I didn’t have the remaining connectors at home but it looks good.

Now to test it. Lets clip together some leads and run it from the bench supply.

Works like a charm. Thumbs up!