Above makes sense -- as an observation. This may have changed in newer Duet iterations, but my original 1.02 version had odd behavior when powered from a 5V in -- the 5v power pins on the PanelDue and the BL Touch read 4.2-4.5 -- I had to ramp up on the input voltage to over 5.6v to get closer to 5v and still the panel due didn't like the lowered voltage. So I scrapped that idea, I didn't like the 7 screen being on all the time anyway, so I am using a more robust power system. A bit overkill, but here is my solution. I have a 4 channel relay module (common on amazon) -- I have a raspberry pi which is used for the camera streaming anyway, so I attached a small 3.5v cheap SPI screen to it and have a little webapp on that screen which currently displays 4 buttons, printer on/off, light on/off -- the light control is done through my home automation system, because it's there, and there is room on the LCD, so the webapp has the Pi toggle all 4 relays, and 2 relays bridge neutral and hot to the 24v PSU, and the the other 2 relays bridge neutral and hot for my heated bed (presently 1kw 120v, soon to be 1.2kw) -- this works really well as 2 relays per connection ensure that there is no way for the bed to be powered even with leakage current from the SSR (which even the best SSRs do leak when off)