250:1 Micro Metal Gearmotor HPCB 6V with 12 CPR Encoder, Side Connector

Overview

Our Micro Metal Gearmotor family consists of tiny brushed DC metal gearmotors with nitride-hardened martensitic stainless steel gears in a wide range of gear ratios, motor windings, brushes, and encoder configurations:

The following comparison table shows basic specifications for all of the available versions (see the Micro Metal Gearmotor datasheet (5MB pdf) for additional information, including detailed performance graphs):

Note: Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. The recommended upper limit for instantaneous torque is 2.5 kg⋅cm (35 oz⋅in) for the 380:1 and 1000:1 gearboxes, and 2 kg⋅cm (25 oz⋅in) for all the other gear ratios; we strongly advise keeping applied loads well under this limit. Stalls can also result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes, especially for the versions that use high-power (HP and HPCB) 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; lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.

Motor windings/brush options

The 6V and 12V HPCB motors have long-life carbon brushes, and they offer the same performance at their respective nominal voltages, just with the 12 V motor drawing half the current of the 6 V motor. The 6V HP, MP, and LP motors have shorter-life precious metal brushes, which are generally lower-friction than carbon brushes and preferred for lower-current applications. The HPCB versions (shown on the left in the picture below) can be differentiated from versions with precious metal brushes (shown on the right) by their copper-colored terminals. Note that the HPCB terminals are 0.5 mm wider than those on the other Micro Metal Gearmotor versions (2 mm vs. 1.5 mm), and they are about 1 mm closer together (6 mm vs. 7 mm).

Micro Metal Gearmotor HPCB long-life carbon brushes (left) next to Micro Metal Gearmotor HP precious metal brushes (right).

Encoder options

Micro Metal Gearmotor (standard version without encoder or extended motor shaft).

Micro Metal Gearmotor with 12 CPR encoder, back connector (cable not included).

Micro Metal Gearmotor with 12 CPR encoder, side connector (cable not included).

Micro Metal Gearmotor with extended motor shaft.

In addition to standard versions that are not intended for use with encoders, we have versions of our Micro Metal Gearmotors available with integrated 12 CPR quadrature encoders on the motor shafts (i.e. on the inputs to the gearbox). These are available in two styles—back connector and side connector—and work with our assortment of 6-pin JST SH-style cables and 6-pin JST SH-style connector boards (cables are not included). A plastic snap-on housing covers the encoder disc and electronics.

We also have motor versions available with an extended motor shaft for adding your own encoder. This 1 mm diameter shaft extends 4.5 mm from the rear of the motor and rotates at the same speed as the input to the gearbox. These versions work with our separately available encoders for Micro Metal Gearmotors.

Gearbox options

The table below shows the exact gear ratios for our Micro Metal Gearmotors. All gearboxes have the same overall dimensions except for 1000:1, which is 3.5 mm longer than the others. The gearboxes use brass plates on all versions except 380:1, which has steel plates for increased durability and resistance to wear from radial loads.

Please note that the higher gear ratios can generate enough torque to damage themselves if exposed to loads beyond what they are rated for (25 kg⋅mm for 1000:1 and 380:1, 20 kg⋅mm for everything else). The point of these higher gear ratios is not to deliver more overall torque but rather to allow for slower speeds at a given voltage and to draw less current for a given torque within its rated operating range.

Dimensions

Our Micro Metal Gearmotors all have gearboxes with a 10 × 12 mm cross section and a 9 mm-long, 3 mm-diameter D-shaped gearbox output shaft. The gearbox length is the same for all gear ratios except 1000:1, which is 3.5 mm longer than the others. On versions without an encoder, the motor fits entirely within the 10 × 12 mm gearbox cross section. The two encoder options fit within the gearbox cross section on the side opposite the connector and extend past it by 3 mm or 4 mm on the connector side, depending on the connector orientation; for the other two sides, the encoder extends past the gearbox cross section by 0.25 mm.

In terms of size, these gearmotors are very similar to Sanyo’s popular 12 mm NA4S DC gearmotors, and gearmotors with this form factor are sometimes also referred to as N20 motors. The versions with carbon brushes (HPCB) have slightly different terminal and end-cap dimensions than the versions with precious metal brushes, but all of the other dimensions are identical.

See our detailed dimension diagrams (635k pdf) for more information.

Details for item #5197

Micro Metal Gearmotor with 12 CPR encoder, side connector.

Gearmotor details:

motor/brush type	gearbox	encoder
HPCB 6V: high-power 6V with carbon brushes	248.98:1 with brass plates		12 CPR incremental quadrature with side connector

Key specifications:

voltage	no-load performance	stall extrapolation*
6 V	130 RPM, 150 mA	3.2 kg⋅cm (44 oz⋅in), 1.5 A
* Note: Stall torque and stall current specifications are theoretical values; stalls could damage the motor or gearbox.

Exact gear ratio: ``(25×34×37×35×38) / (12×10×10×14×10) ~~ bb(248.98:1)``

Using the encoder

This gearmotor includes an integrated two-channel incremental Hall effect encoder that senses the rotation of a magnetic disk on a rear protrusion of the motor shaft. The quadrature encoder provides a resolution of 12 counts per revolution (CPR) of the motor shaft when counting both edges of both channels. To compute the counts per revolution of the gearbox output, multiply 12 by the gearbox reduction factor. For example, for a 50:1 gearbox, the encoder would provide approximately 617 CPR of the gearbox output shaft (see exact gear ratios above).

Micro Metal Gearmotor with 12 CPR encoder, side connector.

Micro Metal Gearmotor with 12 CPR encoder, back connector.

The encoder features a 6-pin JST SH-style male connector that works with our 6-pin JST SH-style cables and 6-pin JST SH-style connector boards. Two connector orientations are available: Back Connector, which is oriented parallel to the motor, and Side Connector, which is perpendicular to the motor. Note: A cable is not included with this gearmotor.

The motor terminals are connected to the M1 (pin 1) and M2 (pin 2) connector pins, and they can be accessed via the red and black wires when used with our corresponding JST cables. For consistency, M1 always connects to the motor terminal marked with a “+” on the back of the motor case. This mark is not visible on the encoder versions because the board covers it, but it can be seen on the versions without encoders. Please note that this is just an identifying mark, and the motor is intended to be operated in both directions by alternating the polarity of the power to the motor leads. Because the two connector types have pin 1 on opposite sides, they have to be mounted with different motor orientations to ensure pin 1 always connects to the same motor terminal, regardless of encoder style.

The sensors are powered through the Vcc (pin 3, blue wire) and GND (pin 6, green wire) pins; Vcc can be 2.7 V to 18 V. The quadrature outputs A and B (yellow and white wires) are digital signals that are either driven low (0 V) or pulled to Vcc through 10 kΩ pull-up resistors, depending on the orientation of the motor. The sensors’ comparators have built-in hysteresis, which prevents spurious signals in cases where the motor is near a transition point. The A and B signals are square waves with roughly 50% duty cycles that are approximately 90° out of phase. The order of the A-B transitions indicates motor direction, and the frequency indicates motor speed. The following scope capture shows an example of these signals:

Encoder A and B outputs of a magnetic encoder on a high-power (HP) 6V Micro Metal Gearmotor running at 6 V.

Encoder schematic

Motor Accessories

• Wheels and hubs: The Micro Metal Gearmotor’s output shaft matches our assortment of Pololu wheels for 3mm shafts and the Solarbotics RW2i rubber wheel. You can also use our Pololu universal mounting hubs to mount custom wheels and mechanism to the Micro Metal Gearmotor’s output shaft, and you can use our 12mm hex wheel adapter to use this motor with many common hobby RC wheels.

• Mounting brackets: Our mounting bracket (also available in white) and extended mounting bracket are specifically designed to securely mount the gearmotor while enclosing the exposed gears. We recommend the extended mounting bracket for wheels with recessed hubs, such as the Pololu wheel 42×19mm. Our Micro Metal Gearmotors will also work with our 15.5D mm metal gearmotor bracket pair.

• Motor controllers and drivers: We have a number of motor controllers and motor drivers that can be used to control these Micro Metal Gearmotors. In particular, the MP6550 motor driver is well suited for these motors, as are our Motoron M1x550, M2x550, M3S550, and M3H550 chainable serial motor controllers.

• Current sensors: The recommended motor control options above have built-in current sensing, but we also have an assortment of stand-alone Hall effect-based current sensors to choose from:

ACS724LLCTR-2P5AB Current Sensor Carrier -2.5A to +2.5A.

We also incorporate these motors into some of our products, including our Zumo robot and 3pi robot :