Can hardwired power be switched?

[comadose]

With a hardwired cam with parking mode, can you just switch off the hardwired power to force a shutdown? Or do they not have a battery for safe shutdown at all?

 

[Nigel]

Depends on the camera, but the Viofo cameras have a power button on the camera, if you press it then they will turn off until you next start the engine. If "you just switch off the hardwired power" then it will still be off next time you start the engine, and you will likely forget to turn it on again. All dashcams can power down OK if they lose power, either using a battery, using a super capacitor, or using nothing but making sure the memory card is never left corrupt (which tends to lose the last couple of seconds of video, so is not ideal!).

 

[comadose]

I was thinking that a simple Arduino + GPS could turn the cam off when at home. Sounds like it would only need to interrupt power until the car is started again, and then turn the hardwired power back on.

 

[Nigel]

I was thinking that a simple Arduino + GPS could turn the cam off when at home. Sounds like it would only need to interrupt power until the car is started again, and then turn the hardwired power back on.

Yes, you could implement geofencing with that, switching the camera would be no problem. Generally you can just switch the +V BAT wire to the dashcam hardwire kit, leaving the ACC and GND connected.

I would be a little concerned about power consumption of your switching system. Just a relay coil can empty a car battery given time, you would want to implement some form of low voltage shutdown with wake up on ACC signal.

Ideally you would use a dashcam with inbuilt geofencing feature instead, but the dashcam manufacturers seem to be failing to provide us with that feature, which might indicate that it will be more difficult for you to implement than you might expect!

 

[comadose]

I wouldn't use a relay, I'd have a latching MOSFET circuit that came on with accessory power and was held on by the Arduino until the GPS detected being at home, or probably some sort of time-out too.

 

[Nigel]

I wouldn't use a relay, I'd have a latching MOSFET circuit that came on with accessory power and was held on by the Arduino until the GPS detected being at home, or probably some sort of time-out too.

Very good.

I guess the Arduino can spend most of its time asleep, how much power are you expecting it and the GPS to take while parked not at home?

If you stay overnight not at home, maybe for a few days, then I imagine you do need to monitor the voltage levels and turn off when appropriate.

 

[comadose]

I was thinking that the latching MOSFET would power the Arduino and GPS as well, so when it was off at home it would be really off, basically zero power draw. ACC would turn it back on again.

It just need some logic to handle when you start out from home.

 

[comadose]

This is what I had in mind:



The switch on the left is accessory power, the switch on the right is the Arduino. The 12V at the top is hardwired.

You can see that only nano amps flows when off. The accessory power turns the circuit on, and the Arduino holds it on. The logic is pretty simple when you think about it:



Basically just wait until the car has been at home for 5 minutes with the ACC power off, or the battery is low, and then turn off. I'd probably want an override switch for long term parking too.

 

[Panzer Platform]

This is what I had in mind:

View attachment 71928

The switch on the left is accessory power, the switch on the right is the Arduino. The 12V at the top is hardwired.

You can see that only nano amps flows when off. The accessory power turns the circuit on, and the Arduino holds it on. The logic is pretty simple when you think about it:

View attachment 71930

Basically just wait until the car has been at home for 5 minutes with the ACC power off, or the battery is low, and then turn off. I'd probably want an override switch for long term parking too.

You just made Pee-Wee's Breakfast Machine. lol
Why not press the power button?

 

[comadose]

Why not press the power button?

I'll forget.