I'm trying to setup a car dash cam in my car and have run into a bit of an issue. Basically I want to power my camera for 180 seconds from my car battery after I turn off the car.

So I need a circuit that will detect if the car is on (from a 12v connection to fuse box, this connection will have power when car is on) and it will also get power directly from the battery.

So when the car turns off the the circuit will detect that no power is being supplied from the fuse box connection and thus will switch over to the battery connection to power the camera for 180 seconds. When the car turns on again the circuit will detect that the fuse connection has power and will start powering the camera.

I found this on eBay but I'm not sure if this will let me do what I want as stated above.
http://www.ebay.ca/itm/12V-Power-OFF-Delay-Relay-Module-Delay-Circuit-Module-/121125206932

 

Dont know if this is allowed as Automobile mods are forbidden here.

 

Is is because of safety? If so, that's understandable. Thanks anyway.

 

The owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

This thread is against the AAC forum rules, Chapter 6, as seen here:

6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

• Any kind of over-unity devices and systems
• Automotive modifications
• Devices designed to electrocute or shock another person
• LEDs to mains
• Phone jammers
• Rail guns and high-energy projectile devices
• Transformer-less power supplies

This can be found in our Terms of Service (ToS)

Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

Please try to understand the reasons behind this action, and feel free to browse and use the forums.

You might find answers to your questions in one of these forums:

http://forum.allaboutcircuits.com/showthread.php?t=54400

Another good forum that shares many of the same membership is http://www.electro-tech-online.com/ . Good luck.