Detect car ignition on and off - send pulse / pulse relay of GoPro camera.

Simple question really but I've forgotten the basics. I need to turn on a Gopro camera when my car ignition is turned on, i.e. 12v (the go pro has interface via an iPod dock like connector and I'll simply short two pins - need to short then for about 3 seconds). Now when the car ignition is turned off I need to shot the pins again - this is where I'm stuck. Need to detect the rise of the 12v send pules then the fall, send pulse - op amp, simple capacitor draining ..... ??????

I'm building a car DVR out of my go pro hence the need to turn the camera on and off when the car ignition is on - gorpo has a kool feature called one touch recording.

Use optocoupler for that, dont put any additional load on ignition contact lock.

You dont even need ignition lock, You can make circuit which will sens difference between turned off engine 12V-12,73V and when engine is on 13,8V-14,2V from lighter plug or similar.

tpetar said:

Use optocoupler for that, dont put any additional load on ignition contact lock.

You dont even need ignition lock, You can make circuit which will sens difference between turned off engine 12V-12,73V and when engine is on 13,8V-14,2V from lighter plug or similar.

Click to expand...

I assume the 12v or around there is the same where ever I tap into it. I basically need to send a pulse to the go pro when I turn the ignition on then when I turn it off I need another pulse, not sure how an op amp would be able to do this? Need to detect the rise of the 12v then the fall and send a pulse on the leading and trailing edge, must be a simple circuit to do that.

tranny said:

I assume the 12v or around there is the same where ever I tap into it. I basically need to send a pulse to the go pro when I turn the ignition on then when I turn it off I need another pulse, not sure how an op amp would be able to do this? Need to detect the rise of the 12v then the fall and send a pulse on the leading and trailing edge, must be a simple circuit to do that.

Click to expand...

But we supose that you have working alternator in function when start engine, this will give us different voltage level, when car is off or on.

And one big thing if you use this based on voltage level. If car is older tech production, there is problem. If you turn lights and other heavy consumer voltage will drop, but if car is newer and have new generation of alternators there is no problems you will get always the same voltage level from it.

Maybe you have some small indicator lamp which is turned on on dashboard which can be used with optocoupler to sense state of car.

Or you can use dc current sensor switch (hall sensor).


See this circuit :

CAR BATTERY AND ALTERNATOR MONITOR
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I actually need a pulse, one for about 2 seconds when the ignition is turned on and another pulse when the ignition is turned off. The gopro needs two terminals to be shorted( pin 12 to ground) for about 3 seconds to turn it on, then three seconds to turn it off again.

Not sure if the above can do this. I was actually going to use a little micro controller as I need more functionality but wondered if there was perhaps an analog / cheaper solution.

Use simple transistor/capacitor delay circuit.

tpetar said:

Use simple transistor/capacitor delay circuit.

Click to expand...

Can you post a circuit.