I have a residential gate with a mag-lock that is set to normally closed. It is controlled by an intercom system. When a resident enters their code the mag-lock is energized and allows entry.

I want to add a "push to exit" button. The intercom system does not allow this to be integrated. So I will need to provide the mag-lock with 12v from the "push to exit" button.

My question is how do i provide 12v to the mag-lock from two different 12v switched inputs? I don't want to have any back flow that could damage the intercom system. I have used simple automotive relays to control lights and the like, but I cannot wrap my head around this problem. Thank-you in advance for any help.

 

Are you sure it requires 12v to UNlock and not a constant 12v to remain locked, assuming it is a magnetic lock? If it's an electromagnet lock that requires 12v to remain locked, then just add a normally closed button along the magnet power wire somewhere. Pressing the button will interrupt the 12v and unlock the gate.

If it really does require 12v to UNlock and you're worried about sending power back to the main system, then just use a diode on the 12v supply from the main system.

 

Normally you can isolate the two 12 volt sources with diodes. Values depending on the current requirements.
SG

 

Add a Schottky rectifier/diode in series with the intercom output.
The diode current rating should be at least 1.5 times the solenoid current.
That will prevent any other applied voltage from damaging the intercom output .

Then you can apply the 12V to the solenoid from any source (PB switch or relay) without problem.
It won't need a diode.

 

Are you sure it requires 12v to UNlock and not a constant 12v to remain locked, assuming it is a magnetic lock? If it's an electromagnet lock that requires 12v to remain locked, then just add a normally closed button along the magnet power wire somewhere. Pressing the button will interrupt the 12v and unlock the gate.

If it really does require 12v to UNlock and you're worried about sending power back to the main system, then just use a diode on the 12v supply from the main system.

Thank you for all the replies. Ill check the voltages next week. I have meetings and obligations the next couple of days.

 

Is the device an electric strike? Unlike what I think of as a magnetic lock, an electric strike remains locked with zero power applies, and takes little power to release. A photo of the device would help. Also, check the operating current if you can.

ak