This gearmotor is a powerful 12V brushed DC motor with a 18.75:1 metal gearbox and an optional integrated quadrature encoder that provides a resolution of 64 counts per revolution of the motor shaft, which corresponds to 1200 counts per revolution of the gearbox’s output shaft.
These units have a 16 mm-long, 6 mm-diameter D-shaped output shaft
These motors are intended for use at 12 V, though in general, these kinds of motors can run at voltages above and below the nominal voltage (they can begin rotating at voltages as low as 1 V). Lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.
Note: Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. In order to avoid damaging the gearbox, we recommend keeping continuously applied loads under 10 kg-cm (150 oz-in), and the recommended upper limit for instantaneous torque is 25 kg-cm (350 oz-in). Stalls can also result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes; a general recommendation for brushed DC motor operation is 25% or less of the stall current.
|Size:||37D × 68L mm1|
|Shaft diameter:||6 mm2|
|No-load speed @ 12V:||530 rpm|
|No-load current @ 12V:||0.2 A|
|Stall current @ 12V:||5.5 A3|
|Stall torque @ 12V:||8.5 kg·cm3|
|Max output power @ 12V:||12 W|
|No-load speed @ 6V:||270 rpm4|
|No-load current @ 6V:||0.15 A4|
|Stall current @ 6V:||3.0 A5|
|Stall torque @ 6V:||5.0 kg·cm5|
Performance at maximum efficiency
|Max efficiency @ 12V:||55 %|
|Speed at max efficiency:||470 rpm|
|Torque at max efficiency:||1.0 kg·cm|
|Current at max efficiency:||0.76 A|
|Output power at max efficiency:||5.0 W|
|Lead length:||20 cm6|
|Encoder resolution:||64 CPR|
1 Length measurement is from gearbox face plate to back of encoder cap (it does not include the output shaft). See dimension diagram for details.
2 D shaft.
3 Stalling is likely to damage the gearmotor. Stall parameters come from a theoretical extrapolation of performance at loads far from stall. As the motor heats up, as happens as it approaches an actual stall, the stall torque and current decrease.
4 This motor will run at 6 V but is intended for operation at 12 V.
5 Stalling is likely to damage the gearmotor. Stall parameters come from a theoretical extrapolation of performance at loads far from stall. This motor will run at 6 V but is intended for operation at 12 V.
6 May vary by a few centimeters.
- Exact gear ratio: (25x30x30)/(10x10x12)=18.75:1
- Dimensional drawing
Warning: Do not screw too far into the mounting holes as the screws can hit the gears. We recommend screwing no further than 3mm (1/8″) into the screw hole.
Using the Encoder
A two-channel Hall effect encoder is used to sense the rotation of a magnetic disk on a rear protrusion of the motor shaft. The quadrature encoder provides a resolution of 64 counts per revolution of the motor shaft when counting both edges of both channels. To compute the counts per revolution of the gearbox output, multiply the gear ratio by 64. The motor/encoder has six color-coded, 8″ (20 cm) leads terminated by a 1×6 female header with a 0.1″ pitch, as shown in the main product picture. If this header is not convenient for your application, you can pull the crimped wires out of the header or cut the header off. The following table describes the wire functions:
|Red||motor power (connects to one motor terminal)|
|Black||motor power (connects to the other motor terminal)|
|Blue||encoder Vcc (3.5 – 20 V)|
|Yellow||encoder A output|
|White||encoder B output|
The Hall sensor requires an input voltage, Vcc, between 3.5 and 20 V and draws a maximum of 10 mA. The A and B outputs are square waves from 0 V to Vcc approximately 90° out of phase. The frequency of the transitions tells you the speed of the motor, and the order of the transitions tells you the direction. The following oscilloscope capture shows the A and B (yellow and white) encoder outputs using a motor voltage of 12 V and a Hall sensor Vcc of 5 V:
By counting both the rising and falling edges of both the A and B outputs, it is possible to get 64 counts per revolution of the motor shaft. Using just a single edge of one channel results in 16 counts per revolution of the motor shaft, so the frequency of the A output in the above oscilloscope capture is 16 times the motor rotation frequency.