This compact, inexpensive plastic gearmotor (brushed DC motor with a 120:1 reduction gearbox) is well suited for use in small robots. While intended for operation at 4.5 V, it should run comfortably in the 3 V to 6 V range. The gearbox has a 9.7mm-long, 3 mm-diameter D-shaped output shaft that is perpendicular to the motor shaft, and a built-in safety clutch helps protect the gears from excessive loads. This version also has a 5×1.5 mm extended motor shaft.
Key specs at 4.5 V: 120 RPM and 80 mA free-run, 20 oz-in (1.4 kg-cm) and 0.8 A stall.
These brushed DC gearmotors are compact and affordable — perfect for building a quick, miniature robot. They are intended for use at 4.5 V, though in general, these kinds of motors can run at voltages above and below this nominal voltage, so they should operate comfortably in the 3 V to 6 V range (rotation can start at voltages as low as 0.5 V). Lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor. The plastic gearbox is protected by a built-in safety clutch that will typically slip before the gear teeth can shear (typically when the load exceeds around 25 oz-in, or 2 kg-cm).
The mini plastic gearmotor family offers two output shaft orientations relative to the motor shaft (offset and 90°), two motor options (normal and high-power, or HP for short), and two gearbox options (120:1 and 180:1). The 120:1 versions are white and the 180:1 versions are yellow:
Some versions of these gearmotors are also available with an additional 1.5 mm-diameter output shaft that protrudes from the rear of the motor. This 5 mm-long rear shaft rotates at the same speed as the input to the gearbox and offers a way to add an encoder, such as our magnetic encoder for mini plastic gearmotors, to provide motor speed or position feedback:
Please see the mini plastic gearmotor comparison table for detailed specifications of all our mini plastic gearmotors. This dynamically-sortable table can help you find the gearmotor that offers the best blend of speed, torque, and current-draw for your particular application.
The gearmotors in the table above all have a 3 mm diameter D-shaft output. These shafts are just like the ones on our micro metal gearmotors and are compatible with many Pololu wheels and our 3 mm universal mounting hubs. We also carry two low-power, 120:1 mini plastic gearmotors with 2 mm diameter spline outputs: 90° 2mm spline output and offset 2mm spline output. These gearmotors all work with our wide and tall mounting brackets for mini plastic gearmotors.
This item has a low-power motor (800 mA stall current), a 120:1 gearbox, and a 3 mm diameter “D”-shaped output shaft that is perpendicular to the motor shaft. The 1.5 mm diameter motor shaft extends approximately 5 mm past the base of the motor. See the dimension diagram (70k pdf) of this gearmotor for more information.
Wheels and hubs: The mini plastic gearmotor output shaft matches our assortment of Pololu wheels and the Solarbotics RW2i rubber wheel. You can also use our 3 mm universal mounting hubs to mount custom wheels and mechanism to the output shaft, and you can use our 12mm hex wheel adapter to use this motor with many common hobby RC wheels.
Mounting brackets: Our wide and tall mounting brackets are specifically designed to securely mount these mini plastic gearmotors. Both brackets work with both offset and 90° gearmotor versions, and the two brackets each allow for different mounting options.
Quadrature encoders: Our magnetic encoder pair kit for mini plastic gearmotors is designed specifically for these motors:
Motor controllers and drivers: We have a number of motor controllers that make it easy to drive these mini plastic gearmotors, including our qik 2s9v1 dual serial motor controller and our programmable Baby Orangutan and Orangutan SVP robot controllers. The qik 2s9v1 allows variable speed and direction control of two small, brushed DC motors using a simple serial interface; the Orangutans combine a programmable Atmel AVR microcontroller and dual motor driver all in a single package and make interfacing with the motor drivers simple when you use our Pololu AVR library. We also carry a number of basic motor drivers suitable for use with these motors, including the DRV8838 single-channel motor driver carrier, the DRV8833 dual motor driver carrier, the DRV8835 dual motor driver carrier, and the TB6612FNG dual motor driver carrier.
The 120:1 gear ratio versions have white plastic bodies and the 180:1 gear ratio versions have yellow plastic bodies (see the main product picture).
Size: 54.5 x 20 x 13.8 mm1
Weight: 19.5 g
Shaft diameter: 3 mm
Shaft type: 90° 3mm D
Typical operating voltage: 4.5 V
Gear ratio: 120:1
Free-run speed @ 4.5V: 120 rpm
Free-run current @ 4.5V: 80 mA
Stall current @ 4.5V: 800 mA
Stall torque @ 4.5V: 20 oz·in2
Extended motor shaft?: Y
1 See drawing for detailed dimensions.
2 Note: the gearbox's built-in clutch might start slipping at a lower torque.
dimension diagram: 90° 3mm D-shaft version (75k pdf)
Dimension diagram of the mini plastic gearmotor with 90° 3mm D-shaft output.
dimension diagram: 90° 3mm D-shaft and extended motor shaft version (70k pdf)
Dimension diagram of the mini plastic gearmotor with 90° 3mm D-shaft output and extended motor shaft.
dimension diagram: 90° 3mm D-shaft and extended motor shaft version HP (70k pdf)
Dimension diagram of the mini plastic gearmotor HP with 90° 3mm D-shaft output and extended motor shaft.
dimension diagram: offset 3mm D-shaft version (77k pdf)
Dimension diagram of the mini plastic gearmotor with offset 3mm D-shaft output.
dimension diagram: offset 3mm D-shaft and extended motor shaft version (69k pdf)
Dimension diagram of the mini plastic gearmotor with offset 3mm D-shaft output and extended motor shaft.
dimension diagram: offset 3mm D-shaft and extended motor shaft version HP (69k pdf)
Dimension diagram of the mini plastic gearmotor HP with offset 3mm D-shaft output and extended motor shaft.
MATLAB script to plot motor performance curves for Pololu brushed DC gearmotors
This MATLAB script, written by Ali Asgher Mansoor Habiby, plots speed, power, current draw, and efficiency as they vary with torque when you input the gearmotor specifications. It also prints the resistance of the motor, and the current draw and torque at which maximum efficiency and maximum power occur.