120:1 Mini Plastic Gearmotor, Offset 3mm D-Shaft Output, Extended Motor Shaft

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 Pololu 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:

180:1 mini plastic gearmotor offset 3mm D-shaft output.

120:1 mini plastic gearmotor, 90-degree 3mm D-shaft output, extended motor shaft.

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 Pololu's magnetic encoder for mini plastic gearmotors, to provide motor speed or position feedback:

Magnetic Encoder Kit for Mini Plastic Gearmotors assembled on mini plastic gearmotors with extended motor shafts.

Please see the mini plastic gearmotor comparison table for detailed specifications of all Pololu's 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. A more basic comparison table is available below:

Motor Type	StallCurrent@ 4.5 V	No-LoadSpeed@ 4.5 V	Stall Torque@ 4.5 V	90° output	90° output + motor shaft	offset output	offset output + motor shaft
high-power(HP)	1250 mA	150 RPM	25 oz-in	120:1 mini HP	120:1 mini HP	120:1 mini HP	120:1 mini HP
low-power	800 mA	120 RPM	20 oz-in	120:1 mini	120:1 mini	120:1 mini	120:1 mini
		80 RPM	30 oz-in	180:1 mini		180:1 mini

Note: The stall torque values listed are approximate, and the built-in safety clutch might start slipping at lower torques.

The gearmotors in the table above all have a 3 mm diameter D-shaft output. These shafts are just like the ones on Pololu's micro metal gearmotors and are compatible with many Pololu wheels and Pololu's 3 mm universal mounting hubs. Pololu 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 Pololu's wide and tall mounting brackets for mini plastic gearmotors.

Details for item #1516

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 offset from but parallel 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 (69k pdf) of this gearmotor for more information.

Exact gear ratio: 22×38×44×26×3010×11×11×22×9≈119.76" role="presentation" style="position: relative;">22×38×44×26×3010×11×11×22×9˜119.76$\frac{22\times 38\times 44\times 26\times 30}{10\times 11\times 11\times 22\times 9}˜119.76$

Motor Accessories

• Wheels and hubs: The mini plastic gearmotor output shaft matches Pololu's assortment of Pololu wheels and the Solarbotics RW2i rubber wheel. You can also use Pololu's 3 mm universal mounting hubs to mount custom wheels and mechanism to the output shaft, and you can use Pololu's 12mm hex wheel adapter to use this motor with many common hobby RC wheels.

Mini Plastic Gearmotor, 90° 3mm D-shaft Output with Pololu Wheel 90×10mm.

Mini plastic gearmotor offset 3mm D-shaft output with Pololu wheel.

Mini Plastic Gearmotor, 90° 3mm D-Shaft Output with Pololu Wheel 32×7mm.

• Mounting brackets: Pololu's 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.

60×8mm Pololu wheel and 90° mini plastic gearmotor mounted with tall mini plastic gearmotor bracket (with spacer).

60×8mm Pololu wheel and offset mini plastic gearmotor mounted with a tall mini plastic gearmotor bracket (with spacer).

80×10mm Pololu wheel and offset mini plastic gearmotor mounted with a wide mini plastic gearmotor bracket.

• Quadrature encoders: Pololu's magnetic encoder pair kit for mini plastic gearmotors is designed specifically for these motors:

The Magnetic Encoder Kit for Mini Plastic Gearmotors works with Pololu's Tall (left) and Wide (right) Mini Plastic Gearmotor Brackets.

• Motor controllers: Pololu offer a number of motor controllers that make it easy to drive these mini plastic gearmotors.
  • The Qik 2s9v1 Dual Serial Motor Controller allows variable speed and direction control of two small, brushed DC motors using a simple serial interface. An Arduino library is available to make communication easier and multiple units can be daisy-chained together if you need to independently control many motors from a single serial bus.
  • The programmable Baby Orangutan B-328 Robot Controller combines a programmable ATmega328P AVR microcontroller and dual motor driver all in a single, very compact, package and makes interfacing with the motor drivers simple when you use Pololu's Pololu AVR library.

Pololu qik 2s9v1 dual serial motor controller (older version with large silver electrolytic capacitor).

Baby Orangutan B-48/B-168/B-328.

• Motor drivers: Pololu also carry a number of basic motor drivers suitable for use with these motors.
  • The DRV8835 Dual Motor Driver Carrier is a great option for driving 2 of these mini plastic gearmotors, especially if space is limited. Aside from its tiny size, it has the benefit of supporting two control interfaces: IN/IN and PHASE/ENABLE. Pololu also carry a DRV8835 dual motor driver shield that makes it easy to incorporate this driver into an Arduino project, as well a DRV8835 motor driver kit for the Raspberry Pi.
  • The DRV8838 Single Brushed DC Motor Driver Carrier is essentially a smaller, lower-cost, single-channel alternative to Pololu's DRV8835 carrier.
  • The MAX14870 Single Brushed DC Motor Driver Carrier is another great single-channel alternative that also offers optional current limiting. This driver is also available as Dual MAX14870 motor driver shield for Arduino and a Dual MAX14870 motor driver kit for the Raspberry Pi to make it easy to incorporate into a two-motor application.

DRV8835 dual motor driver carrier.

DRV8838 Single Brushed DC Motor Driver Carrier.

MAX14870 Single Brushed DC 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).

People often buy this product together with:

Pololu Ball Caster with 1/2" Metal Ball

Pololu Wheel 60×8mm Pair - Black

Magnetic Encoder Pair Kit for Mini Plastic Gearmotors, 12 CPR, 2.7-18V

Dimensions

Size:	36.5 x 20 x 27.4 mm1
Weight:	19 g
Shaft diameter:	3 mm2

General specifications

Shaft type:	offset 3mm D
Typical operating voltage:	4.5 V
Gear ratio:	120:1
No-load speed @ 4.5V:	120 rpm
No-load current @ 4.5V:	80 mA
Stall current @ 4.5V:	800 mA
Stall torque @ 4.5V:	20 oz·in3
Extended motor shaft?:	Y

Notes:

1

See drawing for detailed dimensions.

2

D shaft.

3

Note: the gearbox's built-in clutch might start slipping at a lower torque.

File downloads

• 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.

Recommended links

• 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.