Cherry Pi III USB and XBox power box

This is a small box that allows me to connect an unmodified power plug from an XBox 203W PSU to my Cherry Pi delta printer (http://www.thingiverse.com/thing:543303). It also provides a way to turn the PSU on and off, either with the switch or by using the PS-ON connection on the RAMPS board, and to connect a USB lead.

Although designed to fit a Cherry Pi, it should also work for any similar printer that uses 2 rails made from 20x20 aluminium extrusion and M5 t-nuts.

UPDATE: (26/04/15)

I've added 2 more mounting holes to make the box more secure - the extra holes will only work if the 2 extrusions are approx. 30mm between centres. It can still be used with just 2 screws.

Also, the FreeCAD file has had an error removed by a member of the FreeCAD forum - this made it difficult to edit the design, although the end product wasn't affected.

UPDATE: (27/05/15)

It proved necessary to redesign this box as the XBox PSU proved inadequate - but it wasn't easy to change the design in FreeCAD. The new design is written in OpenSCAD, and is (mostly) parametrized. See http://www.thingiverse.com/thing:851611

Instructions

The case and it's lid were made using PLA, 0.3mm layer height, 33% fill, 2 perimeters and 2 layers top and bottom. The case isn't an economical design - expect to use around 6 metres of 3mm filament!

You will have to arrange these 2 parts to print properly - the box should sit on its back face when printing, and the front plate should sit on its face (reinforcement upwards). You will need to use support for the case (specifically for the PSU socket plinth) but not for the cover. The holes may need to be cleaned out with drills - 5mm for the case mounting holes, 2.5mm for the USB socket mounting holes, and 3mm for the case lid fixing holes. Don't drill out the lid fixing holes in the case.

The lid is designed to be a snug fit to the case - you may need to scrape here and there to get it to fit nicely.

The XBox socket was wired up using ideas lifted from http://www.instructables.com/id/XBOX-360-Power-Supply-to-12V-Accessory-Adapter/step9/Essential-Info-The-Pinout/, with slight changes to allow the wires to come out at right-angles to the casing. The socket is fastened to the case using No.4 x 5/8" (16mm) self-tapping screws from underneath. You will need to use some heat-shrink over the +5v and Power-Enable soldered joints; I also blobbed some 'Liquid Tape' insulation over the bare power wiring once I was sure that the connections were good. I had to trim the springy bits off the of the socket casing so that the USB socket would have enough room to fit.

The USB socket was the end of a short USB-A Male to USB-A Female extension lead plugged into the Arduino board that drives RAMPS: this is held to the faceplate using M2.5 screws.

The round SPDT switch fits into a 20mm diameter hole with a cut-out on the right (included in the front plate). The switch is wired with the Power-Enable wire connected to the centre terminal, the PSU's +5v wire to the the terminal that's connected when the switch is on, and the wire from the RAMPS PS-ON pin to the terminal that's connected when the switch is off. I can't be more specific as terminals vary between switches!

The front plate is fixed with No.4 x 1/2" (13mm) self-tapping screws - the 16mm ones would probably work as well. Don't screw them in too hard, as they're an easy fit and you risk stripping the threads in the plastic.

IMPORTANT NOTES: These parts were designed as a one-off part for my printer and are unlikely to evolve any further. They were created using FreeCAD and making apparently minor changes in that application can be remarkable difficult - the source files are included if you really want to change things, but be it on your own head!

There is a slight flaw in the faceplate, specifically the small cut-out on the switch hole. This doesn't affect the print in any way: neither Cura nor Slic3r complain about it. I've applied a fix using NetFab anyway...