Quote:
Originally Posted by Mashman
You do not want to power the camera from the reverse light signal, but you can control a relay with it. The problem is that voltage on the reverse signal drops when the car is running. You might get 12v with the engine off, the ignition on, and the car in reverse, but when you turn the engine on, the voltage drops to around 9v. When people try to power reverse camera's directly from the reverse signal they often see the camera working fine with the engine not running, but once the engine is on, the camera does not work correctly.
What you can do is power a simple relay off the reverse signal. I don't know if you are familiar with relays, so I will describe how a simple relay works.
Below is a good diagram of how a relay works. What a relay does is it allows for a small current to be used to throw a switch for a larger current. Positions 85 and 86 are for the small current, such as the reverse light signal. When there is power on that current, a coil is energized and forms an electromagnet. Position 30 is connected to constant power, such as the battery (or you can use anything that will have power when you want, such as the amplifier), and position 87 is connected to what you want to have switched power - ie the camera. When the coil does not have power, and spring will keep 30/87 circuit open, when the coil is energized the electromagnet overcomes the spring, and the 30/87 circuit is closed, and power is available on position 87 - the camera.
Many backup camera's have a relay internally, that is why they have three wires, one for power, one for ground, and a separate control wire. Often the radio is only putting out a low voltage control signal, this is not enough to power the camera, and that may be your issue. It's hard to say without knowing what wires you have for your camera, and where they are connected.
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Looking to do this with an Auto Vox V2 soon which I believe only has a power wire (that's supposed to tap the reverse lights). So would something like this be what I need to proceed?
https://www.amazon.com/PACK-AMP-Wate...70_&dpSrc=srch
So based on the attached image below:
I would tap 30 direct to the battery. What fuse size should I use?
87 to the (aftermarket) reverse camera power line.
85 is ground (to chassis), and 86 is the reverse light?. And by the nature of the relay, I won't have to worry about battery drain when the car is not on, correct?