Disable 3v3 to camera and SD-card for solar powered project

With great help from folks here I got a micro SD-card and a VC0706 camera hooked up to my water monitoring electron. They work fine and the only problem is they suck so much current (around 75 - 150 mA) I can’t power them with GPIO pins.
They work fine powered with the 3v3 pin but that doesn’t turn off in deep sleep which is a problem since the system is solar powered and operates through the winter.
I understand from other posts here that I can use a digital pin and a N-MOSFET to turn off the 3v3 power feed. Unfortunately my understanding of electronics diagrams is minimal. Pointers for an electronics idiot would be greatly appreciated. In the mean time I’ll continue with trial and error.
thanks, john

You would apply your 3.3V to the external devices as usual and then instead of connecting the GND pins of the external devices to GND on the controller board, you’d go to the N-MOSFET’s Drain pin and connect its Source pin to GND.
This way the transistor acts like a switch that cuts or closes the circuit on the low side.

When the Gate is supplied with a LOW signal the transistor blocks (cuts the circuit - like an open switch) and when you set it HIGH the transistor opens (becomes conductive - like a closed switch).

To provide that signal you can use any free GPIO pin.

Thanks once again. This looks pretty straight forward. I’m curious though, why on the low side?
thanks, john

You can read up on that here

ScruffR, With your help I got the unit working and using a NpN to disconnect the ground for the camera and Sd-card.

The camera prefers 5v but will run on the 3v of the electron. Unfortunately with the NpN in place there is some voltage drop across the transistor (as mentioned in the article you provided) and the camera gets very flaky.
As long as I power the VC0706 camera from the 3v3 pin and ground directly to a ground pin on the electron the camera works fine.

So I’m back to my original setup of powering the camera from the 3v3 pin, grounding directly to the electron and worrying that the camera will slowly drain the battery during deep sleep since it remains powered by the 3v3 pin. Is that a valid concern?
Seems like if the camera is not taking photos and there is not a stray short to ground maybe it would not draw any current even as it remains powered during deep sleep.

I’m running some tests now to see if the camera does actually cause battery drain during deep sleep but wondering if my worries are just unfounded.
thanks, john

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You should be able to use the Li+ pin to get the full LiPo power to drive the camera.
Alternatively you can use a boost-converter like this.

This even has a Sleep pin to power it of when not needed.
I have used that one for another camera project with Electron

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