Can the raspi 7 inch touch screen be powered by a spare raspi 3 USB port?

Question

Can the element14 raspi 7 inch touchscreen be powered by a spare raspi 3 USB port without damaging the screen?

balearicdynamics · Answer

Hello Nathan,

As a matter of fact if you take a look in depth to the powering connections between the Pi and the screen you see that you can power it in several ways:

power the screen board with the micro USB and from the regular USB plug power the PI
Power the screen with the micro USB and with the two wires from the GPIO on the PI power the device

In theory I think no but I also suppose you don't damage the USB port (hardware). Probably you get and unstable device. As you can see in this post https://www.raspberrypi.org/documentation/hardware/display/ it specifically recommends:

Power the setup via the PWR IN micro-USB connector on the display board. Do not power the setup via the Pi's micro-USB port: the input polyfuse's maximum current rating will be exceeded as the display consumes approximately 400mA.

so the resulting current load needed by the screen should be higher than what is supplied by the USB ports. Maybe that the B3 can do this job but you should try and see what happens testing the entire assembly with some power consuming application (that stress the CPU.

Maybe it works supposing that nothing else is attached to the PI USB but if your project includes some other USB connection I have some doubts.

Enrico

balearicdynamics · Answer

Add-on

A good screening of the current available at the end points of the pins and other parts of the PI (including the reason, limitations and end components can be found here: GPIO Electrical Specifications, Raspberry Pi Input and Output Pin Voltage and Current Capability

Enrico