Power supply options for 120v ac input switching


I’m stuck on my project. I’m building a single enclosure that has a Spark, RPi, screen and 4 SSR inside with one single input of 120v AC. It has 4 outputs of 120v AC that will be controlled by the SSRs. I need to convert some of the incoming power to 5v DC to run the Spark, RPi and screen. I was considering just wiring in a small AC-DC converter for this.

Something like this…

Is this possible? I suppose another option would be to hook up one of those wall plate outlets with USB outputs. Any suggestions of what would be best here? Could you re-purpose an Apple charger? Any suggestions would be appreciated.

Also, what would be the recommended amperage for output? Would 2A be correct for the RPi and Spark?

I am slowly assembling my BrewPi. I, too, am putting everything inside a large enclosure. For safety reasons I decided to feed the mains power from outside to a regular outlet inside. This outlet is mounted onto a surface-mounted electrical back-box. Inside the back-box is the relay board and a fuse. Two separate single outlets are mounted on the outside of the outer box, and a cable goes from the relay board to each outlet. A low-voltage cable from the Pi enters the electrical back-box to drive the relays, and a plastic divider inside the back-box keeps the low-voltage and mains voltage parts separated (in case a wire should come loose inside).

I will plug a USB plug-pack into the mains outlet inside the box which will power the Pi, which is also inside the box.

So, if someone were to open the outer box it will be safe. They will see an outlet with the USB PSU in it. They will see the mains supply cable enter the outer box and go straight into the inner electrical back-box. They will see the two switched mains cables going to the electrical sockets on the outside of the box. So all the mains stuff is touch-safe with the outer box opened, and any exposed wiring is all low-voltage. To access the mains a person would have to remove the cover of the inner electrical outlet, or the outlets on the outside.

Regarding power requirements, I expect a 2A USB supply to be adequate.

Very interesting. Sounds like you have some direction. I decided to use one of these :


I think I’ll just go micro usb to the RPi from here and then connect the screen and Spark to the RPi and hope that powers it all okay.