I am making a device that is composed of a RPi 3 and another circuit that draws max 20 mA.
I want to power both devices from a single wall supply; the RPi schematic shown below shows that PP1 is accessible before the F1 fuse. I am going to use PP1 as my 5V lead to my 20 mA circuit, and also connect this circuit back to RPi's ground. I am going to have a 5V/1A power supply; if my RPi draws no more than 700 mA (and probably doesn't get close to this as I'm not running USB peripherals).
Would anyone suggest it is not a good idea for me to draw 20 mA from PP1 as I've described above? Thanks.