Does Access Control locking hardware require a diode or MOV?

Whenever an output relay drives/controls an inductive load (electromechanical device), a suppression device is recommended to be installed to protect the circuitry. External protection is not required if the device being driven already has internal protection. For more information, refer to the device’s installation manual.

Note: If the lock has internal protection and an external diode or MOV is added, unexpected lock behaviors may occur such as delayed or failed unlocking.

If protection is not installed, the relay’s contacts may be damaged and prematurely fail.

For inductive loads such as a door strike, relay, or solenoid, the suppression device is typically a diode. For 12 or 24 VDC devices, use 1N4002 or equivalent. For MAG locks, the suppression device must be a Metal Oxide Varistor (MOV).

Important: Regardless of the suppression type used, install it as close to the device being driven as possible.