LP 12V Motor with 48 CPR Encoder for 25D mm Metal Gearmotors (No Gearbox)

This motor with integrated 48 CPR (counts per revolution) quadrature encoder is intended as a replacement low-power (LP) 12 V motor with encoder for Pololu's 25D mm metal gearmotors. It is intended for use at 12 V, but in general, these kinds of motors can run at voltages above and below this nominal voltage. Lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

The output shaft has a non-removable pinion gear that works with all of Pololu's 25D mm gearmotor gearboxes. Note that Pololu 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 2 mm.

Other motor windings with identical dimensions and pinion gears are also available, resulting in five total options:

• High-power 6 V motor with encoder
• Low-power 6 V motor with encoder
• High-power 12 V motor with encoder
• Medium-power 12 V motor with encoder
• Low-power 12 V motor with encoder (this product)

These motors are functionally identical to the previous versions Pololu carried without end caps (they use the same motor and encoder). The black plastic end cap is easily removable if you need to access the encoder or want to slightly reduce the overall motor size, but there is a little bit of base plastic that will remain, as shown in the picture below:

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). The LP 12V versions of Pololu's 25D mm metal gearmotors consist of this motor combined with different gearboxes. Pololu 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.

Rated Voltage	Motor Type	Stall Current	No-Load Current	Gear Ratio	No-Load Speed (RPM)	Extrapolated Stall Torque		Max Power (W)	Without Encoder	With Encoder
						(kg · cm)	(oz · in)
12 V	High-Power (HP)	5.0 A	250 mA w/o encoder 300 mA with encoder	1:1 (no gearbox)	10,000	0.4	5.5	10	–	item #4840
				4.4:1	2200	1.7	24	9.4	item #3201	item #4841
				9.7:1	1000	3.9	54	10	item #3202	item #4842
				20.4:1	500	7.4	100	9.4	item #3203	item #4843
				34:1	300	11	150	8.9	item #3204	item #4844
				47:1	220	15	210	8.4	item #3205	item #4845
				75:1	130	22	310	–	item #3206	item #4846
				99:1	100	29	400	–	item #3207	item #4847
12 V	Medium-Power (MP)	1.8 A	80 mA w/o encoder 100 mA with encoder	1:1 (no gearbox)	8200	0.17	2.4	3.5	–	item #4860
				4.4:1	1800	0.71	10	3.2	item #3225	item #4861
				9.7:1	800	1.7	24	3.4	item #3226	item #4862
				20.4:1	380	3.2	44	3.1	item #3227	item #4863
				34:1	230	4.7	65	2.8	item #3228	item #4864
				47:1	170	6.4	89	2.8	item #3229	item #4865
				75:1	100	8.5	120	2.3	item #3230	item #4866
				99:1	79	11	150	2.3	item #3231	item #4867
				172:1	46	18	250	2.1	item #3232	item #4868
				227:1	35	24	330	–	item #3233	item #4869
12 V	Low-Power (LP)	0.9 A	50 mA w/o encoder 60 mA with encoder	1:1 (no gearbox)	5600	0.14	1.9	1.8	–	item #4880
				4.4:1	1200	0.53	7.4	1.7	item #3249	item #4881
				9.7:1	580	1.3	18	1.8	item #3250	item #4882
				20.4:1	280	2.4	33	1.7	item #3251	item #4883
				34:1	170	3.7	51	1.6	item #3252	item #4884
				47:1	120	4.8	67	1.4	item #3253	item #4885
				75:1	75	7.1	99	1.4	item #3254	item #4886
				99:1	57	8.7	120	1.2	item #3255	item #4887
				172:1	33	13	180	1.1	item #3256	item #4888
				227:1	25	16	220	1.0	item #3257	item #4889
				378:1	15	23	320	–	item #3258	item #4890
6 V	High-Power (HP)	6.0 A	420 mA w/o encoder 500 mA with encoder	1:1 (no gearbox)	10,000	0.3	4	7	–	item #4800
				4.4:1	2200	1.2	17	6.7	item #1570	item #4801
				9.7:1	1000	2.3	32	5.9	item #1571	item #4802
				20.4:1	480	4.8	67	5.9	item #1572	item #4803
				34:1	290	6.8	94	5.1	item #1573	item #4804
				47:1	210	9.1	130	4.9	item #1574	item #4805
				75:1	130	14	190	4.5	item #1575	item #4806
				99:1	99	15	210	3.9	item #1576	item #4807
				172:1	57	27	380	–	item #1577	item #4808
6 V	Low-Power (LP)	2.0 A	100 mA w/o encoder 120 mA with encoder	1:1 (no gearbox)	6200	0.15	2.1	2.1	–	item #4820
				4.4:1	1300	0.63	8.7	2.1	item #1581	item #4821
				9.7:1	630	1.3	18	1.9	item #1582	item #4822
				20.4:1	290	2.5	35	1.9	item #1583	item #4823
				34:1	180	3.9	54	1.7	item #1584	item #4824
				47:1	130	4.8	67	1.5	item #1585	item #4825
				75:1	80	7.5	100	1.5	item #1586	item #4826
				99:1	61	9.1	130	1.4	item #1587	item #4827
				172:1	35	14	190	1.2	item #1588	item #4828
				227:1	27	17	240	1.1	item #1589	item #4829
				378:1	16	25	350	–	item #1590	item #4830
				499:1	12	31	430	–	item #1591	item #4831

Note: The listed stall torques and currents are theoretical extrapolations; units will typically stall well before these points as the motors heat up. Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. The recommended upper limit for continuously applied loads is 4 kg·cm (55 oz·in), and the recommended upper limit for intermittently permissible torque is 8 kg·cm (110 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.

25D mm metal gearmotor with 48 CPR encoder (with end cap removed).

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:

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

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.

Dimensions

General specifications

Notes:

1

Length does not include the motor shaft. See dimension diagram for details.

2

This motor does not have a gearbox.

3

Typical; ±20%.

4

Typical, ±50%; no-load current depends on internal friction, which is affected by many factors, including ambient temperature and duration of motor operation.

5

Stalling is likely to damage the motor. 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.

6

May vary by a few inches.

File downloads

• Datasheet for Pololu 25D Metal Gearmotors (2MB pdf)

• Dimension diagram of the Pololu 25D Metal Gearmotors (171k pdf)

• 3D models of 25D mm gearmotors (10MB zip)

  This file contains 3D models (in the step file format) of the 25D mm gearmotors with and without encoders.