99:1 Metal Gearmotor 25Dx69L mm HP 12V with 48 CPR Encoder

These cylindrical brushed DC gearmotors are available in a wide range of gear ratios and with five different motors (two power levels of 6 V motors and three power levels of 12 V 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). The motor and encoder portion is available by itself (no gearbox) for each combination of power level and nominal operating voltage, and versions without the encoder are also available. See the 25D metal gearmotor datasheet (2MB pdf) for more information, including detailed performance graphs for each gearmotor version. You can also use Pololu's dynamically sortable 25D gearmotor comparison table to search for the version that offers the best combination of speed, torque, and current draw for your particular application. A more basic comparison table is available below.

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.

In general, these kinds of motors can run at voltages above and below their nominal voltages (they can begin rotating at voltages as low as 1 V); lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

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

Details for item #4847

Exact gear ratio: 22×22×22×22×22×2312×10×10×10×10×10≈98.78:1" role="presentation" style="position: relative;">22×22×22×22×22×2312×10×10×10×10×10˜98.78:1$\frac{22\times 22\times 22\times 22\times 22\times 23}{12\times 10\times 10\times 10\times 10\times 10}˜98.78:1$

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 (171k pdf).

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

Warning: Do not screw too far into the mounting holes as the screws can hit the gears. Pololu recommend screwing no further than 6 mm (0.24") into the screw hole.

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, 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 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.

Gearmotor accessories

The face plate has two mounting holes threaded for M3 screws. You can use Pololu's 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 encoder mounted to 25D mm bracket.

The 4 mm diameter gearbox output shaft works with Pololu multi-hub wheels as shown in the left picture below. That shaft also works with the Pololu universal aluminum mounting hub for 4mm shafts, which can be used to mount Pololu's larger Pololu wheels (60mm-, 70mm-, 80mm-, and 90mm-diameter) or custom wheels and mechanisms to the gearmotor’s output shaft as shown in the right picture below.

Pololu 80×10mm multi-hub wheel on a Pololu 25D mm metal gearmotor with encoder.

Pololu 60×8mm wheel with 4mm hub adapter on Pololu 25D mm metal gearmotor with encoder.

Alternatively, you could use Pololu's 4mm scooter wheel adapter to mount many common scooter, skateboard, and inline skate wheels to the gearmotor’s output shaft as shown in the left picture below. For a general-purpose hex adapter, consider Pololu's 12mm hex wheel adapter, which lets you use this motor with many common hobby RC wheels as shown in the right picture below.

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

12mm hex wheel adapter for 4mm shaft on a 25D mm metal gearmotor with encoder.

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 as shown in the image below:

Dagu Wild Thumper wheel 120×60mm (metallic red) and Pololu 25D mm metal gearmotor with encoder.

Pololu have a number of motor drivers and motor controllers that work with these 25D mm metal gearmotors. For the LP and MP versions, Pololu recommend Pololu's TB9051FTG-based drivers, for which Pololu have a basic single carrier, a dual-channel shield for Arduino, and a dual-channel expansion board for Raspberry Pi. For the HP versions, Pololu recommend Pololu's VNH5019-based motor drivers (available as single and dual carriers), though these can also be a good choice for the lower-power motors.

TB9051FTG Single Motor Driver Carrier.

Pololu dual VNH5019 motor driver shield for Arduino.

If you are looking for higher-level control interfaces, such as USB, RC, analog voltages, I²C, or TTL serial, consider Pololu's Simple Motor Controllers, Jrk motor controllers, or RoboClaw 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).

High-Power Simple Motor Controller G2 18v15.

Jrk G2 21v3 USB Motor Controller with Feedback.

RoboClaw 2×7A Motor Controller (V5B) in its included case.

Pololu 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.

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.

People often buy this product together with:

Pololu Universal Aluminum Mounting Hub for 4mm Shaft, #4-40 Holes (2-Pack)

Pololu Universal Aluminum Mounting Hub for 4mm Shaft, M3 Holes (2-Pack)

Pololu 25D mm Metal Gearmotor Bracket Pair

Dimensions

General specifications

Performance at maximum efficiency

General specifications

Notes:

1

Length measurement is from gearbox face plate to back of encoder cap (it does not include the output shaft). See dimension diagram for details.

2

D shaft.

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 gearmotor. 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

This motor will run at 6 V but is intended for operation at 12 V.

7

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.

• 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 Pololu generally recommend against it, and Pololu 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 Pololu do not know how well such a modification will work out.