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Pololu Optical Encoder Pair for Micro Metal Gearmotors (extended rear shaft)

Pololu Optical Encoder Pair for Micro Metal Gearmotors (extended rear shaft)

£7.75 incl VAT
(£6.46 exc. tax)
Price in points: 1292 points
4.00 g.
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Add quadrature encoders to your micro metal gearmotors (extended back shaft version required) with this kit consisting of two sensor boards, two 3-tooth encoder wheels, and two 5-tooth encoder wheels. The installed system does not exceed the 12mm × 10mm cross section of the motors and extends only 5mm beyond the plastic motor end cap. The 3-tooth wheel provides 12 counts per revolution; using the 5-tooth wheel yields 20 counts per revolution. This version is intended for use at 3.3V.


This set includes sensor boards and reflective wheels to add quadrature encoding to two micro metal gearmotors with extended back shafts. 3-tooth and 5-tooth encoder wheels are included to provide options of 12 counts per revolution and 20 counts per revolution of the motor shaft (to compute the encoder counts per revolution of the gearbox output, multiply by the gear ratio). Because the encoder board outputs are direct phototransistor outputs, some signal conditioning is often necessary between the sensor and a digital system processing the signals.

Note: This sensor system is intended for relatively advanced users comfortable with the physical encoder installation and with using the resulting signals. It only works with micro metal gearmotors that have extended back shafts.

Pinout and Installation

The encoder board is designed to be soldered directly to the back of the motor, with the back shaft of the motor protruding through the hole in the middle of the circuit board. The better aligned the board, the better the output signal quality will be. One way to achieve good alignment is to tack down the board to one motor pin and to solder the other pin only when the board is well aligned. Be careful to avoid prolonged heating of the motor pins, which could deform the plastic end cap of the motor or the motor brushes. Once the board is soldered down to the two terminals, the motor leads are connected to the M1 and M2 pads along the edge of the board, along with the power for the sensors and the two quadrature outputs:

The edge connections are on a 2 mm pitch. The board can be soldered perpendicularly to another PCB, to a 2 mm connector, or to individual wires as shown above.

Once the board is soldered to the motor, the plastic encoder wheel can be pushed onto the motor shaft. The encoder wheel should be pushed on far enough that the gap between the wheel and sensors is approximately 0.5 mm. One way to get consistent gaps is to use a few sheets of paper or a business card as a shim when installing the encoder wheel. The best way to confirm optimal placement of the encoder wheel is to look at the signal with an oscilloscope.



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Has the problem about the motors you sell not having the extended shafts been resolved yet? I would like to order the following motor 1451-420, and would like to know if it is compatible with the this optical encoder?

Asked by James | 17/02/2015, 14:54 | 1 answer(s)

The description states these are designed to go with a micro metal gearmotors (extended back shaft version required) but I cant find the extended rear shaft versions on the website. Can you point me in the right direction for a Pololu 150:1 Micro Metal Gearmotor HP with extended rear shaft?

Asked by Ben Crundwell | 21/11/2014, 16:16 | 1 answer(s)

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