Make your cheap power supply a little more safe with this cap, and more recently, a cap that accommodates an IEC320-style pluggable-cord (like on computer monitors).

One can find these power supplies pretty easily from online sellers - they're probably made for LED lighting systems but seem to make a decent 12V supply with enough current to drive a project or 3Dprinter gear. The one pictured here is a 12.5Amp unit (model S-150-12). They're only $10-15 typically depending on how much current you want. (many on eBay stores)

Anyway, with the exposed 120V or 220V input terminals, and the high-current DC outputs, you want to be careful with them. So I made a simple end-cap that fits snugly in and is secured with a single self-tapping M3 screw.

The same cap fits on either end. Just print it twice.

You may wish to adjust the cord outlet hole size for whatever cords you wish to use. And you should do something for strain-relief (so that tugging on the cord isn't pulling on the electrical connection. Good options are tying a knot in the leads, or using a big glob of adhesive in the hole.

I also suggest putting lugs on your wires to connect to the screw terminals. Maybe a fuse somewhere too?

Anyway - use at your own risk - but maybe you'll find it a convenient way to get a quick power supply like I did.

Five Years Later: I've added a version to support a standard IEC320 jack, like the one on the backs of monitors. You can get a jack cheap in the same places you get the power supply. See pics. Download the IEC320 version in the STL files.

A future revision may include a switch - or a fused switch!