Overview

These cylindrical brushed DC gearmotors are available in a wide range of gear ratios and with five different motors (two power levels of 6V motors and three power levels of 12V motors). The gearmotors all have the same 25 mm diameter case and 4 mm diameter gearbox output shaft, so it is generally easy to swap one version for another if your design requirements change (though the length of the gearbox tends to increase with the gear ratio). All versions are also available with an integrated 48 CPR quadrature encoder on the motor shaft. Please see the 25D metal gearmotor comparison table for detailed specifications of all our 25D metal 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:

Rated
Voltage
Motor Type Stall
Current
@ Rated Voltage
No-Load
Speed
@ Rated Voltage
Approximate
Stall Torque
@ Rated Voltage


With Encoder


Without Encoder
6 V high-power
(HP)
6.5 A 10,000 RPM 5 oz-in 1:1 HP 6V w/encoder
2150 RPM 20 oz-in 4.4:1 HP 6V w/encoder 4.4:1 HP 6V
990 RPM 39 oz-in 9.7:1 HP 6V w/encoder 9.7:1 HP 6V
460 RPM 75 oz-in 20.4:1 HP 6V w/encoder 20.4:1 HP 6V
280 RPM 90 oz-in 34:1 HP 6V w/encoder 34:1 HP 6V
200 RPM 115 oz-in 47:1 HP 6V w/encoder 47:1 HP 6V
130 RPM 150 oz-in 75:1 HP 6V w/encoder 75:1 HP 6V
97 RPM 210 oz-in 99:1 HP 6V w/encoder 99:1 HP 6V
56 RPM 350 oz-in 172:1 HP 6V w/encoder 172:1 HP 6V
6 V low-power
(LP)
2.4 A 6200 RPM 2 oz-in 1:1 LP 6V w/encoder
1300 RPM 8 oz-in 4.4:1 LP 6V w/encoder 4.4:1 LP 6V
590 RPM 17 oz-in 9.7:1 LP 6V w/encoder 9.7:1 LP 6V
290 RPM 33 oz-in 20.4:1 LP 6V w/encoder 20.4:1 LP 6V
170 RPM 50 oz-in 34:1 LP 6V w/encoder 34:1 LP 6V
120 RPM 65 oz-in 47:1 LP 6V w/encoder 47:1 LP 6V
78 RPM 95 oz-in 75:1 LP 6V w/encoder 75:1 LP 6V
58 RPM 130 oz-in 99:1 LP 6V w/encoder 99:1 LP 6V
34 RPM 200 oz-in 172:1 LP 6V w/encoder 172:1 LP 6V
25 RPM 220 oz-in 227:1 LP 6V w/encoder 227:1 LP 6V
15 RPM 300 oz-in 378:1 LP 6V w/encoder 378:1 LP 6V
11 RPM 400 oz-in 499:1 LP 6V w/encoder 499:1 LP 6V
12 V high-power
(HP)
5.6 A 10,200 RPM 5.5 oz-in 1:1 HP 12V w/encoder
2250 RPM 23 oz-in 4.4:1 HP 12V w/encoder 4.4:1 HP 12V
1030 RPM 44 oz-in 9.7:1 HP 12V w/encoder 9.7:1 HP 12V
500 RPM 85 oz-in 20.4:1 HP 12V w/encoder 20.4:1 HP 12V
290 RPM 120 oz-in 34:1 HP 12V w/encoder 34:1 HP 12V
210 RPM 165 oz-in 47:1 HP 12V w/encoder 47:1 HP 12V
130 RPM 240 oz-in 75:1 HP 12V w/encoder 75:1 HP 12V
100 RPM 300 oz-in 99:1 HP 12V w/encoder 99:1 HP 12V
12 V medium-power
(MP)
2.1 A 7800 RPM 2.7 oz-in 1:1 MP 12V w/encoder
1700 RPM 11 oz-in 4.4:1 MP 12V w/encoder 4.4:1 MP 12V
770 RPM 22 oz-in 9.7:1 MP 12V w/encoder 9.7:1 MP 12V
370 RPM 42 oz-in 20.4:1 MP 12V w/encoder 20.4:1 MP 12V
220 RPM 63 oz-in 34:1 MP 12V w/encoder 34:1 MP 12V
160 RPM 85 oz-in 47:1 MP 12V w/encoder 47:1 MP 12V
100 RPM 125 oz-in 75:1 MP 12V w/encoder 75:1 MP 12V
76 RPM 165 oz-in 99:1 MP 12V w/encoder 99:1 MP 12V
43 RPM 250 oz-in 172:1 MP 12V w/encoder 172:1 MP 12V
33 RPM 320 oz-in 227:1 MP 12V w/encoder 227:1 MP 12V
12 V low-power
(LP)
1.1 A 5600 RPM 2 oz-in 1:1 LP 12V w/encoder
1200 RPM 8 oz-in 4.4:1 LP 12V w/encoder 4.4:1 LP 12V
560 RPM 15 oz-in 9.7:1 LP 12V w/encoder 9.7:1 LP 12V
260 RPM 29 oz-in 20.4:1 LP 12V w/encoder 20.4:1 LP 12V
150 RPM 43 oz-in 34:1 LP 12V w/encoder 34:1 LP 12V
110 RPM 60 oz-in 47:1 LP 12V w/encoder 47:1 LP 12V
71 RPM 85 oz-in 75:1 LP 12V w/encoder 75:1 LP 12V
55 RPM 115 oz-in 99:1 LP 12V w/encoder 99:1 LP 12V
31 RPM 180 oz-in 172:1 LP 12V w/encoder 172:1 LP 12V
23 RPM 240 oz-in 227:1 LP 12V w/encoder 227:1 LP 12V
14 RPM 320 oz-in 378:1 LP 12V w/encoder 378:1 LP 12V

Note: Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. For these gearboxes, the recommended upper limit for instantaneous torque is 200 oz-in (15 kg-cm); we strongly advise keeping applied loads well under this limit. Stalls can also result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes, especially for the versions that use high-power (HP) motors; a general recommendation for brushed DC motor operation is 25% or less of the stall current.

In general, these kinds of motors can run at voltages above and below their nominal voltages; lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

Details for item #3257

Exact gear ratio: ``(22×22×22×22×22×22×24) / (12×10×10×10×10×10×10) ~~ bb(226.76:1)``

Dimensions

The diagram below shows the dimensions of the 25D mm line of gearmotors (units are mm over [inches]). This diagram is also available as a downloadable PDF (223k pdf).

Dimensions of the Pololu 25D mm metal gearmotors. Units are mm over [inches].

Gearmotor accessories

The face plate has two mounting holes threaded for M3 screws. You can use our custom-designed 25D mm metal gearmotor bracket (shown in the picture below) to mount the gearmotor to your project via these mounting holes and the screws that come with the bracket.

Pololu 25D mm metal gearmotor bracket pair.

Pololu 25D mm gearmotor with bracket.

The 4 mm diameter gearbox output shaft works with Pololu universal aluminum mounting hub for 4mm shafts, which can be used to mount our larger Pololu wheels (60mm-, 70mm-, 80mm-, and 90mm-diameter) or custom wheels and mechanisms to the gearmotor’s output shaft as shown in the left picture below. Alternatively, you could use our 4mm scooter wheel adapter to mount many common scooter, skateboard, and inline skate wheels to the gearmotor’s output shaft as shown in the right picture below.

Pololu 60×8mm wheel on a Pololu 25D mm metal gearmotor.

A 25D mm gearmotor connected to a scooter wheel by the 4 mm scooter wheel adapter.

These are the same type of motors used in the Wild Thumper all-terrain chassis, so the gearbox’s output shaft also works directly with the hex adapters included with the 120mm-diameter Wild Thumper wheels (the left picture below shows a 25D mm gearmotor while the right picture shows the smaller 20D mm gearmotor):

Dagu Wild Thumper wheel 120×60mm (chrome) with Pololu 25D mm metal gearmotor.

Dagu Wild Thumper wheel 120×60mm (metallic red) with Pololu 20D mm metal gearmotor.

For a general-purpose hex adapter, consider our 12mm hex wheel adapter, which lets you use this motor with many common hobby RC wheels.

12mm Hex Wheel Adapter for 4mm Shaft on a 20D mm Metal Gearmotor.

We have a number of motor controllers and motor drivers that work with these 25D mm metal gearmotors. For the LP and MP versions, we recommend our MC33296-based motor drivers, for which we have basic single and dual carriers and a dual-channel shield for Arduino. For the HP versions, we recommend our VNH5019-based motor drivers (available as single and dual carriers), though these can also be a good choice for the lower-power motors because they will run much cooler than the MC33926 carriers. If you are looking for higher-level control interfaces, such as USB, RC, analog voltages, or TTL serial, consider our Simple Motor Controllers, Jrk motor controllers, or TReX motor controllers; these controllers are available in various power levels, and the appropriate one depends on the particular version of 25D mm motor you have (we generally recommend a motor controller that can handle continuous currents above the stall current of your motor).

Pololu dual VNH5019 motor driver shield for Arduino.

Pololu TReX Dual Motor Controller.

Simple Motor Controller 18v7, fully assembled.

We have an assortment of Hall effect-based current sensors to choose from for those who need to monitor motor current:

ACS711EX current sensor carrier -15.5A to +15.5A.

ACS714 current sensor carrier -5A to +5A.

25D mm metal gearmotor with 48 CPR encoder: close-up view of encoder.

Using the encoder (if applicable)

The versions of these gearmotors with encoders use a A two-channel Hall effect sensor to detect the rotation of a magnetic disk on a rear protrusion of the motor shaft. The quadrature encoder provides a resolution of 48 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 48. 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. This header works with standard 0.1″ male headers and our male jumper and precrimped wires. 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:

Color Function
Red motor power (connects to one motor terminal)
Black motor power (connects to the other motor terminal)
Green encoder GND
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 6 V and a Hall sensor Vcc of 5 V:

Encoder A and B outputs for 25D mm HP 6V metal gearmotor with 48 CPR encoder (motor running at 6 V).

By counting both the rising and falling edges of both the A and B outputs, it is possible to get 48 counts per revolution of the motor shaft. Using just a single edge of one channel results in 12 counts per revolution of the motor shaft, so the frequency of the A output in the above oscilloscope capture is 12 times the motor rotation frequency.

Selecting the right gearmotor

We offer a wide selection of metal gearmotors that offer different combinations of speed and torque. Our metal gearmotor comparison table can help you find the motor that best meets your project’s requirements.

Some of the Pololu metal gearmotors.


Specifications

Dimensions

Size: 25D x 56L mm
Weight: 94 g
Shaft diameter: 4 mm

General specifications

Gear ratio: 226.76:1
Free-run speed @ 6V: 11 rpm1
Stall current @ 6V: 550 mA1
Stall torque @ 6V: 120 oz·in1
Free-run speed @ 12V: 23 rpm
Free-run current @ 12V: 100 mA2
Stall current @ 12V: 1100 mA
Stall torque @ 12V: 240 oz·in3
Motor type: 1.1A stall @ 12V (LP 12V)
Encoders?: N

Notes:

1
This motor will run at 6 V but is intended for operation at 12 V.
2
Maximum.
3
This is a theoretical value; stalling the gearbox output shaft is likely to damage the gearbox.

Resources

File downloads

Dimension diagram of Pololu 25D mm Metal Gearmotors (223k pdf)
3D models of 25D mm gearmotors (9MB zip)
This file contains 3D models (in the step file format) of the 25D mm gearmotors with and without encoders.
Modifying the Wild Thumper to use motors with encoders (3MB pdf)

Customer Richard Nguyen has documented his work modifying the Wild Thumper chassis to use 25D motors with encoders in place of the chassis’s included motors.

Note: This is not an easy modification, and the chassis can be damaged if it is not done properly, so we generally recommend against it, and we can only provide very limited support for those who want to attempt it. The manufacturer did not intend for the chassis to be modified in this way, and we do not know how well such a modification will work out.

(PL-3257)

SKU PL-3257
Brand Pololu

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