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20.4:1 Metal Gearmotor 25Dx50L mm LP 12V

Pololu item #: 3251 38 in stock
Brand: Pololu
Status: Active and Preferred 
RoHS 3 compliant
 Free shipping in USA 

Price break Unit price (US$)
1 19.95
10 17.96


backorders allowed

This gearmotor consists of a low-power, 12 V brushed DC motor combined with a 20.4:1 metal spur gearbox. The gearmotor is cylindrical, with a diameter just under 25 mm, and the D-shaped output shaft is 4 mm in diameter and extends 12.5 mm from the face plate of the gearbox. This gearmotor is also available with an integrated encoder.

Key specifications:

voltage no-load performance stall extrapolation
12 V 280 RPM, 50 mA 2.4 kg⋅cm (33 oz⋅in), 0.9 A

Alternatives available with variations in these parameter(s): gear ratio motor type encoders? Select variant…

 Description Specs (19) Pictures (10) Resources (3) FAQs (2) On the blog (0) 

Overview

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). Each version is also optionally available with an integrated 48 CPR quadrature encoder. 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 version that offers the best combination of speed, torque, and current draw for your particular application. A more basic comparison table is available below:

Motor
Type
Rated
Voltage
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)
High-Power
(HP) 12 V
12 V 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
Medium-Power
(MP) 12 V
12 V 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
Low-Power
(LP) 12 V
12 V 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
Motor
Type
Rated
Voltage
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)
High-Power
(HP) 6 V
6 V 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
Low-Power
(LP) 6 V
6 V 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.

Details for item #3251

Exact gear ratio: ``(22×22×22×23) / (12×10×10×10) ~~ bb(20.4:1)``

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 without encoders. Units are mm over [inches].

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

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 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 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 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 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 left picture below. For a general-purpose hex adapter, consider our 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.

We have a number of motor drivers and motor controllers that work with these 25D mm metal gearmotors. For the LP and MP versions, we recommend our TB9051FTG-based drivers, for which we have a basic single carrier, a dual-channel shield for Arduino, and a dual-channel expansion board for Raspberry Pi. 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.

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 our 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.

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.

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.

People often buy this product together with:

Pololu 25D mm Metal Gearmotor Bracket Pair Pololu 25D mm Metal Gearmotor Bracket Pair
Pololu Universal Aluminum Mounting Hub for 4mm Shaft, M3 Holes (2-Pack) Pololu Universal Aluminum Mounting Hub for 4mm Shaft, M3 Holes (2-Pack)

Related Products

Pololu 25D mm Metal Gearmotor Bracket Pair
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 Aluminum Scooter Wheel Adapter for 4mm Shaft
12mm Hex Wheel Adapter for 4mm Shaft (2-Pack)
Dagu Wild Thumper Wheel 120x60mm Pair with 4mm Shaft Adapters - Metallic Red
Dagu Wild Thumper Wheel 120x60mm Pair with 4mm Shaft Adapters - Chrome
Pololu Wheel 60×8mm Pair - Black
Pololu Wheel 90×10mm Pair - White
TB9051FTG Single Brushed DC Motor Driver Carrier
VNH5019 Motor Driver Carrier
Pololu G2 High-Power Motor Driver 24v13
Dual TB9051FTG Motor Driver Shield for Arduino
Pololu Dual VNH5019 Motor Driver Shield for Arduino
Pololu Dual G2 High-Power Motor Driver 24v14 Shield for Arduino
High-Power Simple Motor Controller G2 24v12 (Connectors Soldered)
Jrk G2 24v13 USB Motor Controller with Feedback
Jrk G2 21v3 USB Motor Controller with Feedback
Pololu Qik 2s12v10 Dual Serial Motor Controller

Related Categories

12V Low-Power (LP) 25D mm Gearmotors
25D Metal Gearmotors
Pololu Wheels and Tracks
RoboClaw Motor Controllers
Brushed DC Motor Controllers
Brushed DC Motor Drivers
Robot Controllers
Current Sensors
37D Metal Gearmotors
20D Metal Gearmotors
Micro Metal Gearmotors
Wild Thumper All-Terrain Chassis
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