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Thread: VCRX Contact Closure Input compatibility with Liftmaster 3800/8500 Door Lock signal

  1. #1
    Junior Member
    Join Date
    Jun 2014

    VCRX Contact Closure Input compatibility with Liftmaster 3800/8500 Door Lock signal

    I have a Liftmaster 5800/3800 MyQ controlled garage door system as well as a RA2 VCRX controlled overhead garage light, that I am trying to get to play nice together . I have a couple questions before I end up taking the smoke out and not being able to put it back in ;-).

    What I would like to do is utilize the door lock pins on the liftmaster opener to drive the Contact closure input connector on the VCRX so that I can control the lights. Currently I have it programmed so that one of the car's homelink button controls the garage door, and another homelink button controls the overhead light. (I have nice industrial overhead garage lights) and opted not to use the cheap plastic light , hence the dilemma.

    The Liftmaster garage door lock is essentially a 12 Volt car door lock mechanism that when operated pulses 1.1 - 1.3 amps @13 volts

    In looking at the VCRX Contact Closure Input specs, it says..

    Dry contacts only
    ON saturation: <1 V- at 2 mA
    OFF leakage: <1 μA at 9 VMinimum

    I am in search of a mechanism to wire this up safely without running the risk of damaging the VCRX. Unfortunately Liftmaster's support as has been shown here was not very helpful with the spec for the door lock. (The information on the operation voltage/amps was gleaned from the URL below)

    Anyone have a recommendation on how to wire this up to the VCRX input?

    I want to have a VCRX CCI turn on a RA2 light, and then have that light turn off after a set programmed time.

  2. #2
    Hi irieblue,

    I too considered using the bolt lock as a trigger for the lights, but figured out a better approach. I'm using this device:

    mounted to the side rail of the door, and door railing, connected to the VCRX's input ports (1 and C). Its a strong magnetic dry contact closer, and use it to trigger the overhead recessed lights on / off states based on the garage door being open or closed. Works great!

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