12V Motor with 64 CPR Encoder for 37D mm Metal Gearmotors (No Gearbox, Helical Pinion)

This 12 V motor with integrated 64 CPR (counts per revolution) quadrature encoder is intended as a replacement motor and encoder for Pololu's 12V 37D mm metal gearmotors with helical pinion gears.

The 2mm output shaft has a non-removable pinion gear that works with all of Pololu's “Helical Pinion” 37D mm gearmotor gearboxes. Note that Pololu do not sell the 37D 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.

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

Dimensions

Dimensions of the Motor with 64 CPR Encoder for 37D mm Metal Gearmotors (No Gearbox, Helical Pinion). 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 damage the motor. Pololu recommend screwing no more than 3.5mm (0.14") into the screw hole.

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). Pololu's 37D mm line of 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	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.

This motor is intended for use at 12 V, though in general, these kinds of motors can run at voltages above and below the nominal voltage; lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

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 can be seen in the pictures below that show this motor combined with a gearbox:

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 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 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.

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 measurement does not include motor shaft or pinion gear.

2

This motor does not have a gearbox.

3

Stalling can 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.

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

• Datasheet for Pololu 37D Metal Gearmotors (2MB pdf)

• Dimension diagrams of the Pololu 37D mm Metal Gearmotors (459k pdf)

• 3D models of 37D mm gearmotors (7MB zip)

  This file contains 3D models (in the step file format) of the 37D mm gearmotors with and without encoders.

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.