I ordered a 7 inch hdmi touchscreen for the Raspberry Pi 3 on ebay and started developing my Python openCV application.
So my setup is a Raspberry Pi 3 + webcam + 7 inch touchscreen powered via usb
During development I noticed a lightning bolt icon in the upper right corner. It is a undervoltage warning, so I ordered a 3A power adapter. But this didn't help.
I also noticed my webcam video framerate performance was horrible, but as soon is I powered the touchscreen with a 2nd power adapter instead of via the Pi all my speed and power problems disappeared. The downside is that I don't have any touch input now.
The original setup with touchscreen powered via the Pi draws around 1.1Amps The touchscreen itself draws around 0.9amps
This is measured with a usb power meter, but I'm hesitated if the results are correct, because this will mean Raspberry + webcam is only 0.2amps with running opencv application with 55% CPU.
Are the 4 USB on the raspberry limited to a certain amount of milliamps?
Update: In my /boot/config.txt my max_usb_current is already default set on 1