I got one of your USB power y-cables to use with the 7" touch screen. How powerful should the USB source I plug the y-cable into be to sufficiently run a Pi (say a Pi 4B) and the touch screen?
My recommendation would be to use the official Pi foundation 2.5 A micro USB supply. Still might be iffy with a PI 4. Plus you’ll need and adapter to plug the Y into a Pi 4.
and
@alphanumeric Thanks for the good ideas. I happen to have a Pi 4 (USB-C) power supply. Since USB-C power supplies are going to be showing up more and more, is it possible to use it with the Y-cable for this purpose? In that case, I guess I would need an adaptor that has USB-C female on one end of the adaptor and microUSB male on the other. Is that correct? [edit: and of course I would still need the adaptor you mention if I put a Pi 4 in with the touch screen. If it was < Pi 4, I guess then I would only need the first adapter I mention here. In short: Pi 3 case: (Pi 4 PSU) -> (USB-C-2-microUSB adaptor) -> (Y-cable) -> both (Pi 3) and (TouchScreen). For the Pi 4 situation: (Pi 4 PSU) -> (USB-C-2-microUSB adaptor) -> (Y-cable) -> Both (TouchScreen) and (microUSB-2-USB-C adaptor -> Pi 4)]
I have yet to see an adapter to plug the new USB C power supply into an older Pi with the micro USB.
USB C female to micro USB male.
How are your soldering skills?
You could cut the female Micro USB off and replace it with this.
Then you’d only need the one adapter.
Do you have plans to use the GPIO pins on the PI? I ask because you can power the display with female to female jumpers you plug into the +5V and ground pins on the Pi. My screen came with the jumpers included. I didn’t use them though. I made up my own custom cables feed from a 5V 4A supply.