This gearmotor consists of a high-power, 12 V brushed DC motor combined with a 34.014:1 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 |
290 RPM, 300 mA |
8.5 kg⋅cm (120 oz⋅in), 5.6 A |
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 gearmotor that offers the best blend of speed, torque, and current-draw for your particular application. A more basic comparison table is available below:
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 15 kg-cm (200 oz-in); we strongly advise keeping applied loads well under this limit. Stalls can also result in rapid (potentially on the order of a second) 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 (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 #3204
Exact gear ratio: 22×20×22×22×2312×12×10×10×10≈34.014:122×20×22×22×2312×12×10×10×10≈34.014:1
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).
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| 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.
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| Pololu 25D mm metal gearmotor bracket pair. |
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| Pololu 25D mm gearmotor with bracket. |
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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.
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| Pololu 80×10mm multi-hub wheel on a Pololu 25D mm metal gearmotor with encoder. |
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| Pololu 60×8mm wheel with 4mm hub adapter on Pololu 25D mm metal gearmotor with encoder. |
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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.
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| A 25D mm gearmotor with encoder connected to a scooter wheel by the 4mm scooter wheel adapter. |
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| 12mm hex wheel adapter for 4mm shaft on a 25D mm metal gearmotor with encoder. |
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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:
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| 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.
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| TB9051FTG Single Motor Driver Carrier. |
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| Pololu dual VNH5019 motor driver shield for Arduino. |
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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).
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| High-Power Simple Motor Controller G2 18v15. |
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| Jrk G2 21v3 USB Motor Controller with Feedback. |
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| RoboClaw 2×7A Motor Controller (V5B) in its included case. |
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We have an assortment of Hall effect-based current sensors to choose from for those who need to monitor motor current:
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| ACS711EX current sensor carrier -15.5A to +15.5A. |
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| ACS714 current sensor carrier -5A to +5A. |
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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.
Dimensions
| Size: |
25D x 52L mm1 |
| Weight: |
88 g |
| Shaft diameter: |
4 mm |
General specifications
| Gear ratio: |
34.014:1 |
| No-load speed @ 12V: |
290 rpm |
| No-load current @ 12V: |
300 mA2 |
| Stall current @ 12V: |
5600 mA |
| Stall torque @ 12V: |
120 oz·in |
| No-load speed @ 6V: |
145 rpm3 |
| Stall current @ 6V: |
2800 mA3 |
| Stall torque @ 6V: |
60 oz·in3 |
| Motor type: |
5.6A stall @ 12V (HP 12V) |
| Encoders?: |
N |
Notes:
- 1
- Length measurement is from gearbox face plate to back of motor (it does not include the output shaft or motor terminals). See dimension diagram for details.
- 2
- Maximum.
- 3
- This motor will run at 6 V but is intended for operation at 12 V.
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| 25D mm metal gearmotor. |
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| Pololu 25D mm gearmotor with bracket. |
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| Pololu 60×8mm wheel on a Pololu 25D mm metal gearmotor. |
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| 12mm Hex Wheel Adapter for 4mm Shaft on a 20D mm Metal Gearmotor. |
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| Dagu Wild Thumper wheel 120×60mm (chrome) with Pololu 25D mm metal gearmotor. |
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| Partially disassembled Dagu Wild Thumper 6WD chassis with one of the gearmotors visible. |
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| Encoder A and B outputs for 25D mm HP 6V metal gearmotor with 48 CPR encoder (motor running at 6 V). |
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| Encoder A and B outputs for 25D mm LP 6V metal gearmotor with 48 CPR encoder (motor running at 6 V). |
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| Dimensions of the Pololu 25D mm metal gearmotors without encoders. Units are mm over [inches]. |
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| An assortment of Pololu metal gearmotors. |
Recommended links
- MATLAB script to plot motor performance curves for Pololu brushed DC gearmotors
- This MATLAB script, written by Ali Asgher Mansoor Habiby, plots speed, power, current draw, and efficiency as they vary with torque when you input the gearmotor specifications. It also prints the resistance of the motor, and the current draw and torque at which maximum efficiency and maximum power occur.
I need additional information about this motor; do you have a datasheet?
No; the information we have available for this motor can be found on its product page. However, you can approximate various additional motor parameters from the information found in the “Specs” tab.
The electrical resistance of the motor can be approximated by dividing the rated voltage by the stall current (at the rated voltage). The electromotive force constant (Ke) can be approximated by dividing the rated voltage by the free-run speed (at the rated voltage). To approximate the motor torque constant (Kt), you can divide the stall torque by the stall current.
For pretty much any DC motor, the current, speed, power, and efficiency curves as a function of torque will look like those in the graph below (assuming motor voltage and temperature are constant):
The current and speed curves are approximately linear, and the product pages for our motors provide the approximate end points for these lines: (0 torque, no-load current) and (stall torque, stall current) for the red line, and (0 torque, no-load speed) and (stall torque, 0 speed) for the blue line.
The orange output power curve is the product of the speed and the torque, which results in an inverted parabola with its peak at 50% of the stall torque.
The green efficiency curve is the output power divided by the input power, where the input power is current times voltage. The voltage is constant, so you can divide the output power curve by the current line to get the general shape of the efficiency curve, which in turn lets you identify the torque, speed, and current that correspond to max efficiency.
There are many programs out there that you can use to generate these curves. For example, if you have access to MATLAB, you can use this customer-created MATLAB script to generate these motor plots for you from the specifications we provide for each gearmotor.
Note: A good general rule of thumb is to keep the continuous load on a DC motor from exceeding approximately 20% to 30% of the stall torque. Stalling gearmotors can greatly decrease their lifetimes, occasionally resulting in immediate damage to the gearbox or thermal damage to the motor windings or brushes. Do not expect to be able to safely operate a brushed DC gearmotor all the way to stall. The safe operating range will depend on the specifics of the gearmotor itself.
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