Question About Limit Switches


I want to add a contact sensor to my driveway electric gate. I want to avoid a sensor on the actual gate to stay out of the weather. Sensative strips are unlikely to work due to the gap I have between closed gate and post plus I feel they are still overpriced.

I am wondering if I could tap in to a limit switch the gate system uses to determine open (or closed). See the kind of deal I am talking about below:

I assume these switches are tripping a relay and that they are dry contacts. I can’t go pull the cover and check right now due to rain. If so, my thought is to wire in parallel with one of them (probably the closed side) and use that as a dry contact feed to a Z-Wave contact sensor that has external connections.


(Robin) #2

Those limit switches won’t give you a dry contact because they will be getting a power feed from the gate system… even wiring in parallel to them will apply current to a dry contact sensor which won’t be a good thing… also, the sensor could short-circuit the limit switches causing the gate to malfunction.

You would need to measure the voltage across the limit switches, and buy a dumb relay with a coil voltage to match. Wire the relay to the negative side of the limit switch and ground. Then connect the dry contact sensor to the switched side of the dumb relay.

You could always buy a high strength neodymium magnet (but not too high) to achieve a greater gap for a sensitive strip.


Okay thanks Robin. I just couldn’t find this info anywhere else so I appreciate your input.

Now I just have to wait days for this rain to stop. We can go months without rain, literally, then when I have something I want to do outside in dry weather we have a flash flood watch, lol.