I am trying to build a raspberry pi dashcam. I plan to have the RPi connected to battery and turned on and off with 12v ignition input. The RPi can be turned on and off by shorting 2 pins on the board momentarily.

I started researching relays, which can be made momentary with resistors and capacitors. But with this method I can only turn the RPi on and not off.

I then was considering an electronic circuit using a 555 timer in a monostable config with a XOR module to control a relay, but most XOR modules I can find are rated for 5v max. I want to build the unit into a plastic shroud around my mirror and space is limited. Should I build the XOR gate using surface mount resistors? Or Is there another way?

 

Welcome to AAC!

Wouldn't using an SPST momentary switch be simpler?

 

Yes and that is what I am trying to replicate with the circuitry without the momentary switch (see here: https://howchoo.com/g/mwnlytk3zmm/how-to-add-a-power-button-to-your-raspberry-pi )

The problem comes with convenience as I would need to push the button to turn on the dashcam and then again to turn off every time I got in and out of my car. If I forget to turn off the RPi it drains the battery, if I forget to turn on the RPi it does not record.

 

I am trying to build a raspberry pi dashcam. I plan to have the RPi connected to battery and turned on and off with 12v ignition input. The RPi can be turned on and off by shorting 2 pins on the board momentarily.

I started researching relays, which can be made momentary with resistors and capacitors. But with this method I can only turn the RPi on and not off.

I then was considering an electronic circuit using a 555 timer in a monostable config with a XOR module to control a relay, but most XOR modules I can find are rated for 5v max. I want to build the unit into a plastic shroud around my mirror and space is limited. Should I build the XOR gate using surface mount resistors? Or Is there another way?

Could I use a XOR gate with negative edge triggered and positive edge triggered inputs?