Relay box

This is a simple box for a 5V relay, similar to HL-51 Relay case (https://www.thingiverse.com/thing:1639266). This one has slightly different dimensions and supports parallel power pins rather than vertical. This fits the "Tolako 5V relay module for Arduino":

https://smile.amazon.com/gp/product/B00VRUAHLE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I needed this to replace the fans in an AC Infinity AV rack cooler, which uses hardwired 5V fans. I used 12V Noctua fans, with an external 12V power supply and connected the output of the AC Infinity temperature controller as the power/input for the relay. The controller thinks everything is 5V USB, the relay just translates. And since I now had a 12V source I added a component fan from the same relay (a 200mm fan on top of the AV amplifier).

A comment on the little "walls" on the base on either side: because the relay is on stands it lifts the relay 4mm off the base. This leaves a hole in either side that seems out of place. These little walls fill the space when the cover is attached while still keeping the print "bottoms up" so no support is needed. If you built a "tunnel" in the cover (or the base" you would probably end up needing support, although depending on your printer it might span the gap without too much stringing. I have a hard time "printing" over space without supports.

I might suggest replacing the pins with holes for self-tapping screws. I used automotive putty (it's for molding) to fix the relay to the base, a self tapping screw is more manageable.

The cover just snaps to the base. Given the precision of the print there is a small but consistent amount of tension that is sufficient to hold it in place (it has a 1mm lip). In my application this is perfect, but if there is concern about the cover falling off I might suggest building a clip on the cover to snap over the base. You could use a small screw through an overlap of cover-to-base, but that seems like overkill. The cover has no mechanical force on it.