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Motor with 48 CPR Encoder for 25D mm Metal Gearmotors (No Gearbox)


$27.59 AUD, inc GST
$25.08 AUD, exc GST

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Motor with 48 CPR Encoder for 25D mm Metal Gearmotors (No Gearbox)
27.59 AUD


$27.59 AUD, inc GST
$25.08 AUD, exc GST
Shipping Offer


  • $6.95 Standard (2-4 days, tracked)
  • $8.95 Express (Overnight*, tracked)
  • $3 Economy Post* (3-7 days, no tracking)
  • FREE Pickup (Newcastle only)

Shipping costs may increase for heavy products or large orders.

Exact shipping can be calculated on the view cart page.

*Conditions apply, see shipping tab below.


This motor with integrated 48 CPR (counts per revolution) quadrature encoder is intended as a replacement low-power (non-HP) motor and encoder for Pololu's 25D mm metal gearmotors. The output shaft has a non-removable pinion gear that works with all of Pololu's 25D mm gearmotor gearboxes. Note that we do not sell the 25D mm gearboxes separately, but if you have a gearmotor with a damaged motor or encoder (or if you want to effectively add an encoder to a version without an encoder), you can transfer the gearbox to this replacement motor.

The motor has a diameter of 24.2 mm (0.95 in) and a length of approximately 43 mm (1.7 in) from the top of the motor can to the bottom of the encoder. The top of the motor has two mounting holes threaded for M3 screws. These mounting holes are 17 mm apart and form a line with the motor shaft at the center. The mounting holes have a depth of approximately 6.5 mm.

A higher-power motor with encoder with identical dimensions and an identical pinion gear is also available.

Pinion Gear Specs

  • Metric with module m = 0.4
  • Number of teeth: 12
  • Face thickness: 2.5 mm
  • Pressure angle: 20°
  • Gear position: 4.5 mm from top of motor to top of gear

Gearmotor Options

You will typically want to combine this motor with a gearbox to give it a more appropriate combination of torque and speed (without a gearbox, it offers very high speed with very low torque). Pololu's 25D mm line of metal gearmotors consist of this non-HP motor or an HP motor combined with different gearboxes. We do not carry the gearboxes by themselves, so unless you are looking at this as a replacement motor for a compatible gearbox you already have, Pololu strongly recommend you consider getting a preassembled gearmotor with the gear ratio that best suits your project requirements.

Gear Ratio No-Load
@ 6 V
Stall Torque
@ 6 V
Stall Current
@ 6 V

With Encoder

Without Encoder
1:1 9800 RPM 2 oz-in 6 A motor without gearbox
5600 RPM 1 oz-in 2.2 A motor without gearbox
4.4:1 2220 RPM 8 oz-in 6 A 25Dx48L mm HP
1280 RPM 5 oz-in 2.2 A 25Dx48L mm
9.7:1 1010 RPM 17 oz-in 6 A 25Dx48L mm HP 25Dx48L mm HP
580 RPM 11 oz-in 2.2 A 25Dx48L mm 25Dx48L mm
20.4:1 480 RPM 36 oz-in 6 A 25Dx50L mm HP
275 RPM 24 oz-in 2.2 A 25Dx50L mm
34:1 285 RPM 60 oz-in 6 A 25Dx52L mm HP 25Dx52L mm HP
165 RPM 40 oz-in 2.2 A 25Dx52L mm 25Dx52L mm
47:1 210 RPM 80 oz-in 6 A 25Dx52L mm HP 25Dx52L mm HP
120 RPM 50 oz-in 2.2 A 25Dx52L mm 25Dx52L mm
75:1 130 RPM 130 oz-in 6 A 25Dx54L mm HP 25Dx54L mm HP
75 RPM 85 oz-in 2.2 A 25Dx54L mm 25Dx54L mm
99:1 100 RPM 160 oz-in 6 A 25Dx54L mm HP
57 RPM 110 oz-in 2.2 A 25Dx54L mm
172:1 57 RPM 260 oz-in 6 A 25Dx56L mm HP
33 RPM 170 oz-in 2.2 A 25Dx56L mm 25Dx56L mm
227:1 25 RPM 220 oz-in 2.2 A 25Dx56L mm
378:1 15 RPM 250 oz-in 2.2 A 25Dx58L mm
499:1 12 RPM 300 oz-in 2.2 A 25Dx58L mm

Note: At some of the higher gear ratios, these motors can generate enough torque to damage themselves. Any torque greater than about 250 oz-in (18 kg-cm) is likely to damage the gearbox, so they recommend that you avoid stalling the 172:1 HP, 227:1, 378:1, and 499:1 versions of these motors at 6 V.

These motors are intended for use at 6 V. In general, these kinds of motors can run at voltages above and below this nominal voltage, so they should comfortably operate in the 3 – 9 V range, though they can begin rotating at voltages as low as 1 V. Higher voltages could start negatively affecting the life of the motor.

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

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 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, 11" (28 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 Pololu's 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 (non-HP) 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

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

Some of the Pololu metal gearmotors.
Documentation and Resources:

Product Comments

Exact shipping can be calculated on the view cart page (no login required).

We deliver Australia-wide with these options:

  • $3 for Small Items (3-7 days, not tracked, only available on selected small items)
  • $6.95 for Standard Post (2-4 days, tracked)
  • $8.95 for Express Post (Overnight for Australia Post Next Day Network, tracked)
  • Pickup - Free! Only available to customers who live in the Newcastle region (only after we email you to notify your order is ready)

International Orders - the following rates are for New Zealand and will vary for other countries:

  • $11.49 for Pack and Track (3+ days, tracked)
  • $16.50 for Express International (2-5 days, tracked)

If you order lots of gear, the postage amount might increment based on the weight of your order.

Our physical address (here's a PDF which includes other key business details):

Unit 18, 132 Garden Grove Parade
NSW, 2289

Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.

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