Forum Discussion

Commutator's avatar
Commutator
Explorer
Mar 04, 2014

Can I get voltage sensitive power control?

I'm putting a wireless backup camera on my car hauler trailer and I want it to be powered up only when the truck is running. So I'd like to use the hot feed coming from the truck to power the trailer camera but through some circuitry that works like a voltage sensitive relay. The camera should only get power when the voltage is over 13.7 or something like that to indicate the alternator is running.

I don't have or want a battery in the trailer. The VSRs I've read about seem to require a battery on both sides of the relay to operate, whereas I'm looking for something that has the power source on one side and the load on the other, but only passes power at charging voltages.

Any suggestions how to accomplish this?

Thanks,
Fred

18 Replies

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  • naturist's avatar
    naturist
    Nomad II
    Mar 04, 2014
    The second cheapest solution requires a $1 toggle switch. The cheapest involves disconnecting a wire.
  • dougrainer's avatar
    dougrainer
    Nomad
    Mar 04, 2014
    Commutator wrote:
    Of course there's a breakaway battery, but it's not relevant. I'm not going to use it to power a camera for the obvious safety reasons, plus that would make the camera always-on which is worse than just having it on whenever the truck is connected. I only want the camera on when the truck is connected AND running.

    I'm not going to rework the 7 way connector to get an ignition-hot feed to the trailer so I can use a relay. If I can't find the equivalent of a vsr that works without a battery on the load side of the relay, then I'll just feed the camera from the running lights. But my strong preference is to have it automatically on when truck is running, and off when truck is not.

    Thanks,
    Fred


    I connected the Camera to the rear Running lights on the rear of the trailer. You just turn the Truck headlights OR just the running lights ON to activate the Camera. Doug
  • Commutator's avatar
    Commutator
    Explorer
    Mar 04, 2014
    Of course there's a breakaway battery, but it's not relevant. I'm not going to use it to power a camera for the obvious safety reasons, plus that would make the camera always-on which is worse than just having it on whenever the truck is connected. I only want the camera on when the truck is connected AND running.

    I'm not going to rework the 7 way connector to get an ignition-hot feed to the trailer so I can use a relay. If I can't find the equivalent of a vsr that works without a battery on the load side of the relay, then I'll just feed the camera from the running lights. But my strong preference is to have it automatically on when truck is running, and off when truck is not.

    Thanks,
    Fred
  • enblethen's avatar
    enblethen
    Nomad
    Mar 04, 2014
    A heavy duty relay installed with coil operated off a "run" hot location.
    Relay
    Trailers with brakes must have a battery to operate the breakaway function.
  • OnaQuest's avatar
    OnaQuest
    Explorer
    Mar 04, 2014
    You could adapt one of THESE very easily to do exactly what you want it to do.
    I would think that your trailer required a break-away system that would require a battery for braking..
  • beemerphile1's avatar
    beemerphile1
    Explorer
    Mar 04, 2014
    Continuous duty solenoid triggered by the ignition.



    Around $15 to $20 at your local auto parts.

    Doesn't that trailer have brakes? Brake systems need a battery to work in a breakaway situation. They are required by law above a minimal weight.
  • camperpaul's avatar
    camperpaul
    Explorer
    Mar 04, 2014
    Commutator wrote:

    -- snip --

    I don't have or want a battery in the trailer.

    -- snip --
    Thanks,
    Fred

    You are REQUIRED have a battery in that trailer to operate the brakes in case of "break-away".

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