12v diagram help - Off momentary switch, on ignition

[peteramjet]

This is doing my head in. It’s no doubt simple, but my brain is just not working.

I have a 12v dash camera permanently installed in a car. The camera normally continues in a standby/parking mode while the ignition is off, activating itself by motion.

I’m seeking to have the ability to switch off the camera manually when the car is off (by a momentary push switch) then have the camera automatically turn back on when when the the car is ignition is activated.

Essentially:
- car on, camera on.
- car off, camera on. UNLESS,
- car off, momentarily button pushed, camera off.

Somebody please put my simple mind to rest with an answer on how to get this sorted.

[hinekadon]

fet the supply mombutton in the gate to ground or 12v

[peteramjet]

fet the supply mombutton in the gate to ground or 12v

That’ll switch it off, but won’t the camera restart as soon as the button is released as there is still a 12v feed?

[hinekadon]

the fet will stay to where its pulled ie hi /low

[peteramjet]

the fet will stay to where its pulled ie hi /low

If use the button to switch the gate, that’ll stop the drain. But if I use ignition on the same gate, won’t that switch the fet each time the ignition is cycled, regardless of its previous state?

I feel like I’m missing something obvious here

[peteramjet]

Been through the s-parts box, and all I have access to is automotive relays (NO, NC). Short term I’ll try and get this going with relays only - can’t go out due to lockdown.

Edit: SPST and DT available.

[hinekadon]

think about it as a state you want then build to suit each state in parallel with the others then intersect them

[wotnot]

Latching relay & momentary switch =)

[ammlione]

I think I can do it with an inverter relay (like the one in this picture )

30 Common
87A NC
87 NO
85 Coil
86 Coil
Will need a NO pushbutton (pins 1 & 2)

30 to Battery Positive and pushbutton pin 1
87A to camera
87 to 85 and pushbutton pin 2
86 to GND

(Sorry, don't know how to place a pic here)
Not sure if it is what you want, but beware, the relay coil will use power from your battery when the camera is in the OFF state

Cheers

[peteramjet]

30 to Battery Positive and pushbutton pin 1
87A to camera
87 to 85 and pushbutton pin 2
86 to GND

(Sorry, don't know how to place a pic here)
Not sure if it is what you want, but beware, the relay coil will use power from your battery when the camera is in the OFF state

Cheers

Have 85 and 86 been switched there? In my mind that should read:
- 87 to 86 and push button
- 85 to ground

[peteramjet]

Turns out I was overthinking it

The device attached to the camera (that detects voltage and shuts it off below a set amount) obviously turns off when constant power is cut, and turns back on when it senses power to the acc wire.

Breaking the 12v constant power to this device (with my desired momentary switch and relay) causes the camera to switch off. The camera (via the device) switches back on when acc power is supplied.

I forgot about the functions of the power device already installed, making the fix overly simplistic.

Thanks all.