Geared DC Motor (Gearmotor)
A DC motor manufactured together with a gearbox mounted directly on the motor shaft. The gearbox lowers the speed and raises the torque by the same ratio, so a small, low-current motor can move a heavy load. It is the standard solution in automatic door, barrier and greenhouse screen mechanisms.
Output torque is roughly the motor torque multiplied by the gear ratio and the gear efficiency. Efficiency is typically around 90 percent in a single stage, but can fall to 50–70 percent in multi-stage or worm gearboxes. That loss is reflected directly as current at the driver.
Points that affect driver selection:
- Calculate current from the output: Divide the required output torque by the ratio and the efficiency to find the motor torque, then use the torque constant to find the current.
- Stall happens more easily: With high-ratio gearboxes it is easy to reach the mechanical end stop; current-sensing stop takes advantage of that behaviour.
- Gear backlash: On direction changes there is dead motion equal to the backlash; a soft start ramp prevents that backlash from closing with an impact.
On modules with a ramp adjustment such as the PT500 and KS250, setting the ramp to the shortest time at which the backlash closes quietly improves both mechanical life and starting current.
Where this term is used: DC Motor Driver Selection Guide