Puck.js: power/battery switch off on the "D1 D2 3V GND" part - is it possible from software ?

[espruino-discuss]

Posted at 2020-10-12 by user67655

Hi Everybody,
we have 4 connection points on the bottom right part of Puck: D1, D2, 3V, GND.
Is it possible to switch off this 3V/GND from software?
Many thanks for the answer!

[espruino-discuss]

Posted at 2020-10-12 by @allObjects

3.3V Power and GND: Nope, since it is all hard wired. D1 nd D2 you can put into high impedance (input, without watch on the pin) - if high impedance matches your definition of 'switched off'.

If you want power control, you need to 'sneak in' some small resistor+BJT or FET driven by another pin to drive external power if required current is beyond what the module specifies it can sink or source. If you though want to drive something of the button cell, you do not get very far.

To be of more help, you may reveal a bit more about what you want to do... ;-)

[gfwilliams]

Posted at 2020-10-13 by @gfwilliams

Do you mean for turning Puck.js itself on and off? You can basically do that in software with NRF.sleep() to stop Puck.js from advertising on Bluetooth.

But turning other devices on and off can be done using D1 and D2 as long as they don't draw a lot of power (under 5mA) - connect a device between D1 and GND and you can turn it on with D1.write(1) and off with D1.write(0).

But for higher-power devices (under 200 mA) you can use Puck.js's v2's on-board FET (which is effectively a switch to GND). So you could connect something between the FET pin and the 3v pin, and you can turn that on and off with FET.write(...).

But for higher power stuff you'll need to add an external FET or transistor as @allObjects says, but it's not like you can really draw more than 50mA from the Puck.js battery anyway

[espruino-discuss]

Posted at 2020-10-13 by user67655

Thanks a lot for your answers @allObjects and @gfwilliams !
I have Puck.js v2, so I think the on-board FET will be a great solution for me.
Thank you!

[espruino-discuss]

Posted at 2020-10-13 by @allObjects

Oops... missed the FET option in Puck V2...