LOCK

Main conern: compact size , stall torque.

In electric locks , mostly micro spur gear motors smaller than 25mm diameter are used . In a few high precision locks, high-cost planetary gear motors are aslo applied . The motor solution finally depends on the mechanical design .

In the  past,  the locks used to have DC motors with direct drive system , nowadays , gear motors are replacing them rapidly because of low cost . 

Motors usually will stall at the moment to lock and unlock . So strong gears and stall torque are the main technique difficulties to overcome .