Power management, Feahter and Pro Mini

Projects General Guidance
1

Hi,

Will you take a look at this power setup and see if it is OK? I have omitted all wires that are not vcc or ground.

Parts:

Adafruit Feather 3.3v
Is being powered either by USB or 3.7v LIPO battery.
It has a JST connector for a battery. In the specifications it says:
When the USB power is powered, it will automatically switch over to USB for power, as well as start charging the battery (if attached) at 100mA. This happens 'hotswap' style so you can always keep the Lipoly connected as a 'backup' power that will only get used when USB power is lost.

Arduino Pro Mini 3.3v
Is being powered by the Feathers charger or the battery, if the battery is switched on. I am worried about this part, if the battery is NOT switched on, but the Feather is in USB.

Sparkfun MicroSD Breakout with level shifter
Is being powered from the Pro Mini.

Sparkfun SX1509 I/O Expander (16 pins)
Is being powered from the Feather. Is only connected to buttons - nothing that draws power.

On/Off switch
Is being used to cut the power from the battery and turn the devices off.

1128×984 181 KB

All inputs and recommendations to how I should manage the power is very, very welcome. Thanks!

2

I would give each board its own power and ground from the battery. SD can pull > 80mA at times.

4

Feather will still supply power to the Pro Mini through the battery charger.

The more serious problem would be the Feather supplying power to any unpowered devices through I/O pins. You must make sure this never happens, as both devices can be destroyed.

5

I see. You have to go through the Adafruit Feather which I just found specs for.

It says you can get 500mA peak current through the regulator so it might be reasonable that > 200mA can be used. That ends my concern so far.

7

SomethingClever:
If I connect the SD card breakout to the battery too I don't think this can happen, as either the battery will power both controllers or the USB and Feather will power both.

The Feather board VCC pin should be powered by the on-board power manager. VCC and GND are not I/O pins.

9

All the boards should get power from the Feather power pin and ground to the Feather gound pin.

There is a maximum continuous current, I expect that the Adafruit forum has the answer already posted.