19:1 Metal Gearmotor 37Dx68L mm 12V with 64 CPR Encoder (Helical Pinion)

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Pololu item #: 4751
Brand: Pololu
Status: Active and Preferred 
RoHS 3 compliant


This gearmotor is a powerful 12V brushed DC motor with a 18.75:1 metal gearbox and an integrated quadrature encoder with a resolution of 64 counts per revolution (CPR) of the motor shaft and 1200 CPR of the gearbox’s output shaft. The gearbox is composed mainly of spur gears, but it features helical gears for the first stage for reduced noise and improved efficiency. These units have a 16 mm-long, 6 mm-diameter D-shaped output shaft. This gearmotor is also available without an encoder.

Key specifications:

voltage no-load performance stall extrapolation
12 V 530 RPM, 200 mA 8.5 kg⋅cm (120 oz⋅in), 5.5 A

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

Compare all products in 12V 37D Metal Gearmotors.

Pictures

19:1 Metal Gearmotor 37Dx68L mm with 64 CPR Encoder (Helical Pinion).

19:1 Metal Gearmotor 37Dx68L mm with 64 CPR Encoder (Helical Pinion).

19:1 Metal Gearmotor 37Dx68L mm with 64 CPR Encoder (Helical Pinion).

37D Gearmotor (Helical Pinion) with the gearbox removed showing the helical pinion gear and first mating gear.

37D mm metal gearmotor with 64 CPR encoder connected to a Pololu 90×10mm wheel with a Pololu universal mounting hub.

37D mm metal gearmotor with 64 CPR encoder (with end cap removed).

37D mm metal gearmotor with 64 CPR encoder (with end cap removed).

37D mm metal gearmotor with 64 CPR encoder (with end cap removed).

The 25D and 37D mm metal gearmotors with encoders have cables that are terminated with a 6-pin, 0.1″-pitch female connector.

Encoder A and B outputs for 37D mm metal gearmotor with 64 CPR encoder (12V motor running at 12 V).

Dimensions of the 37D metal gearmotors with 64 CPR encoders. Units are mm over [inches].

37D mm gearmotor (without encoder) with L-bracket and 6mm universal mounting hub.

37D mm gearmotor (without encoder) with L-bracket and 6mm universal mounting hub.

37D mm gearmotor (without encoder) with L-bracket and 6mm universal mounting hub.

37D mm Metal Gearmotor next to a Micro Metal Gearmotor for size comparison.

An assortment of Pololu metal gearmotors.




Overview

Measuring 37 mm (1.46″) in diameter, these brushed DC gearmotors are the largest and most powerful we carry. They are available in a range of gear ratios from 6.3:1 to 150:1 and with 12 V or 24 V motors, and all versions are available with integrated 64 CPR quadrature encoders on the motor shafts. The 12 V and 24 V motors offer approximately the same performance at their respective nominal voltages, with the 24 V motor drawing half the current of the 12 V motor. See the 37D metal gearmotor datasheet (2MB pdf) for more information, including detailed performance graphs for each gearmotor version. You can also use our dynamically sortable 37D 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		 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 5.5 A 0.2 A 1:1 (no gearbox) 10,000 0.5 7 – – item #4750
6.3:1 1600 3.0 42 12 item #4747 item #4757
10:1 1000 4.9 68 12 item #4748 item #4758
19:1 530 8.5 120 12 item #4741 item #4751
30:1 330 14 190 12 item #4742 item #4752
50:1 200 21 290 10 item #4743 item #4753
70:1 150 27 380 10* item #4744 item #4754
100:1 100 34 470 8* item #4745 item #4755
131:1 76 45 630 6* item #4746 item #4756
150:1 67 49 680 6* item #2829 item #2828
24 V 3 A 0.1 A 1:1 (no gearbox) 10,000 0.55 8 – – item #4690
6.3:1 1600 3.5 49 14 item #4688 item #4698
10:1 1000 5.5 76 14 item #4689 item #4699
19:1 530 9.5 130 13 item #4681 item #4691
30:1 330 15 210 13 item #4682 item #4692
50:1 200 23 320 12 item #4683 item #4693
70:1 140 31 430 10* item #4684 item #4694
100:1 100 39 540 8* item #4685 item #4695
131:1 79 47 650 6* item #4686 item #4696
150:1 68 56 780 6* item #4687 item #4697
* Output power for these units is constrained by gearbox load limits; spec provided is output power at max recommended load of 10 kg⋅cm.

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 10 kg-cm (150 oz-in), and the recommended upper limit for instantaneous torque is 25 kg-cm (350 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 the nominal voltages; lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

The gearboxes are composed mainly of spur gears, but they feature helical gears for the first stage for reduced noise and improved efficiency:

37D Gearmotor (Helical Pinion) with the gearbox removed showing the helical pinion gear and first mating gear.

On units with encoders, the encoder portion is protected by a black plastic end cap:

The 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 pictures below:

Details for item #4751

This gearmotor is a powerful 12V brushed DC motor with a 18.75:1 metal gearbox and an integrated quadrature encoder that provides a resolution of 64 counts per revolution of the motor shaft, which corresponds to 1200 counts per revolution of the gearbox’s output shaft. These units have a 16 mm-long, 6 mm-diameter D-shaped output shaft. This gearmotor is also available without an encoder.

Key specifications:

voltage no-load performance stall extrapolation
12 V 530 RPM, 200 mA 8.5 kg⋅cm (120 oz⋅in), 5.5 A

Exact gear ratio: ``(25×30×30) / (10×10×12) = bb(18.75:1)``

Dimensions

Dimensions of the 37D metal gearmotors with 64 CPR encoders. Units are mm over [inches].

This diagram is also available as a downloadable PDF (459k pdf).

Warning: Do not screw too far into the mounting holes as the screws can hit the gears. We recommend screwing no more than 3mm (0.12″) into the screw hole.

37D mm metal gearmotor with 64 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 64 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 64. 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 our 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 12 V motor at 12 V and a Hall sensor Vcc of 5 V:

Encoder A and B outputs for 37D mm metal gearmotor with 64 CPR encoder (12V motor running at 12 V).

By counting both the rising and falling edges of both the A and B outputs, it is possible to get 64 counts per revolution of the motor shaft. Using just a single edge of one channel results in 16 counts per revolution of the motor shaft, so the frequency of the A output in the above oscilloscope capture is 16 times the motor rotation frequency.

Gearmotor accessories

The face plate has six mounting holes evenly spaced around the outer edge threaded for M3 screws. These mounting holes form a regular hexagon and the centers of neighboring holes are 15.5 mm apart. We carry two brackets for these gearmotors: a stamped aluminum L-bracket (sold in pairs) and a sturdier, tombstone-style machined aluminum bracket (sold individually):

37D mm gearmotor (without encoder) with L-bracket and 6mm universal mounting hub.

Pololu machined aluminum bracket for 37D mm metal gearmotors mounting a motor to a clear piece of acrylic.

The 6 mm diameter gearbox output shaft works with the Pololu universal aluminum mounting hub for 6mm shafts, which can be used to mount our larger Pololu wheels (80mm- and 90mm-diameter) or custom wheels and mechanisms to the gearmotor’s output shaft as shown in the left picture below. Alternatively, you could use our 6mm scooter wheel adapter to mount many common scooter, skateboard, and inline skate wheels to the gearmotor’s output shaft as shown in the right picture below:

37D mm metal gearmotor with 64 CPR encoder connected to a Pololu 90×10mm wheel with a Pololu universal mounting hub.

A 37D mm gearmotor connected to a scooter wheel by the 6 mm scooter wheel adapter.

For a general-purpose hex adapter, consider our 12mm hex wheel adapter (also available in an extended version), which lets you use these motors with many common hobby RC wheels, including Dagu Wild Thumper Wheels:

12mm Hex Wheel Adapter for 6mm Shaft connecting a Wild Thumper Wheel to a 37D mm Metal Gearmotor.

We have a number of motor drivers and motor controllers that work with these 37D mm metal gearmotors. We generally recommend our High-Power Motor Drivers, which are available in various power levels and versions, including some dual-channel shields for Arduino and dual-channel expansion boards for Raspberry Pi. Additionally, our VNH5019-based motor drivers, which are also available as single and dual carriers, are a good match for these gearmotors.

Pololu Dual G2 High-Power Motor Driver 24v14 Shield for Arduino.

Pololu Dual G2 High-Power Motor Driver 24v14 for Raspberry Pi (assembled version) with included hardware.

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 several of which can handle these 37D mm metal gearmotors (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.

Dimensions

Size: 37D × 68L mm1
Weight: 200 g
Shaft diameter: 6 mm2

General specifications

Gear ratio: 18.75:1
No-load speed @ 12V: 530 rpm
No-load current @ 12V: 0.2 A
Stall current @ 12V: 5.5 A3
Stall torque @ 12V: 8.5 kg·cm3
Max output power @ 12V: 12 W
No-load speed @ 6V: 270 rpm4
No-load current @ 6V: 0.15 A4
Stall current @ 6V: 3.0 A4
Stall torque @ 6V: 5.0 kg·cm4
Motor type: 12V

Performance at maximum efficiency

Max efficiency @ 12V: 55 %
Speed at max efficiency: 470 rpm
Torque at max efficiency: 1.0 kg·cm
Current at max efficiency: 0.76 A
Output power at max efficiency: 5.0 W

General specifications

Lead length: 20 cm5
Encoders?: Y
Encoder resolution: 64 CPR

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
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.
4
This motor will run at 6 V but is intended for operation at 12 V.
5
May vary by a few centimeters.

File downloads

Recommended links

Frequently-asked questions

Is it okay to stall this motor at its operating voltage?

No! Stalls can 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, which means keeping continuously applied loads around 25% or less of the stall torque.

Additionally, for many of our gearmotors with high gear ratios, the extrapolated stall torque is beyond what the gearboxes are designed to handle, and a stall could instantly damage the gears. Make sure to keep applied loads within the published limits for your gearmotor.

What do the dotted lines mean in the motor performance curves from the datasheet?
In our motor performance curves, the solid lines show the regions where we actually took measurements while the dotted lines show extrapolations beyond that. For many motors, we took measurements out to about 50% of the stall torque, since continued operation at loads past this point increasingly risk thermal damage to the windings. However, for higher gear ratios, going to 50% of the stall torque exceeds what is safe for the gearbox, so the measurements are further limited to not much past our recommendation for continuously applied loads.
What material is the gearbox output shaft made of, and can I get the shaft customized?
The shaft is composed of hardened stainless steel. Some customization is generally possible (e.g., different length or no D-shaft) for sufficiently high-volume orders. If this is something you are interested in, please email us.

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