peter_3d

I haven't done anything like that, and don't know of anyone else who has. Sounds like a good idea, though.

The PoE solution that I added to the writeup is working very well. At my house, I have one touchscreen using the 120V option, and one using the PoE option. Both have been working perfectly for 2+ months. I recommend PoE whenever possible.(You can ignore my comment about 'that adapter wouldn't work'. I bought that adapter, tested it, and that's what I'm using)

Latest update: I purchased some of the parts suggested below (thanks!) and installed one of my touchscreens using Power Over Ethernet. It works great! I updated the Instructable to show both methods of powering the touchscreen.

@wkearney99, thanks for all the thoughts. It's actually a really hard problem. The 3-gang box provides enough space for the Pi hanging off the back of the touch screen, but the remaining space (and shape of that space) is not enough for a USB outlet or any other type of outlet.I'm going to post an update where I no longer wire-wrap the adapter prongs, and instead use an IEC C7 extension cord (see photos below). There will still be a transformer in the box, but it will be easily detachable without tools, so I don't see how that's any different than plugging a transformer into an outlet inside a recessed box.I will update soon and I'll be interested to hear your thoughts on the new version. Thanks for your interest. As you say, it's a tough problem.

Thanks again for all the comments about wiring and safety. I've updated the Instructable with the latest design, which uses a C7 extension cord. This approach eliminates the need to wire-wrap the prongs of the Apple USB adapter.As for the comments about using an electrical box with an embedded, angled location to place a power outlet with USB connectors: I had already looked at those early in the process and I'm afraid they're all much too small. The electronics on the back of the touchscreen require about 2 1/2 spaces of a 3-gang box. This is why my design works so hard to wall off the high-voltage connections in a L-shaped space at the back of the box. Everything could fit in a 4-gang box, but then the bezel would need to be much wider horizontally. I've considered designing and...

Thanks again for all the comments about wiring and safety. I've updated the Instructable with the latest design, which uses a C7 extension cord. This approach eliminates the need to wire-wrap the prongs of the Apple USB adapter.As for the comments about using an electrical box with an embedded, angled location to place a power outlet with USB connectors: I had already looked at those early in the process and I'm afraid they're all much too small. The electronics on the back of the touchscreen require about 2 1/2 spaces of a 3-gang box. This is why my design works so hard to wall off the high-voltage connections in a L-shaped space at the back of the box. Everything could fit in a 4-gang box, but then the bezel would need to be much wider horizontally. I've considered designing and 3D printing an electrical box that meets all the requirements, but that may be a different project altogether.And as I said below, Power Over Ethernet could work well given the right adapter. In my case, cat5 wasn't available at my install locations.

Actually, on closer inspection, it seems that adapter wouldn't work. It supplies 2A at 5V. I observed that if the Pi receives anything less than 2.1 Amps, it shows a low-voltage warning on the screen, and is susceptible to memory corruption. Have you not seen that problem with this adapter?

Thanks for the suggestion that an IEC C7 plug might plug directly into the Apple USB adapter, @HockleyDawg. I bought one and it fits! This will eliminate the need to wire wrap the plugs on the adapter. I will update Instructable this weekend. Thanks very much for the great suggestion!