With respect to the Pi zero; I would really like to know what is dragging 45mA when it is powered off. Cannot find any circuit diagrams and I am not about to reverse engineer the board. Just engineering interest at this time.
If I use an On/Off Shim to power the Pi Zero, current dain is less the 1uA; when powered off.
The Pi Foundation wont publish the circuit diagram because of a past situation where someone made poor quality copies of their boards. Anyway that is what I have read.
PS I can get a Pi Zero to run in idle mode at about 68mA; by disabling display, keyboard, and mouse. So why does it need 45mA when powered off. …
Issuing a shutdown will just be the Linux side of things. The voltage regulator, network hardware, etc, will remain powered. A bit like shutting down a PC, parts of the motherboard often remain powered.
To remove power entirely, an external switch or circuit would be needed to isolate power from the USB power.
Thanks for your reply Graham.
I found a circuit diagram (just the input power) from a web site dedicated to fault finding a non running Pi Zero. PAM2306AYPKE dual voltage, DC to DC converter IC; same as other Pi models.
The light on the Pi Zero going off would make you think it has powered down and use of the command poweroff would do the same. Most likely the low level commands just switch the processor into Standby mode, not Shutdown mode, so the processor is still powered somewhat.
In a battery powered design where the Pi is woken up, does something, then goes back to sleep; use of the Pimoroni On/Off Shim would be the best solution. This device removes power completely.
Anyway, this has been an interesting exercise for me, hopefully this is useful.
Good question. I guess some circuitry needs to be on to allow soft power on.