Magnetic Encoder Pair Kit with Side-Entry Connector for Micro Metal Gearmotors, 12 CPR, 2.7-18V

Overview

This kit includes two dual-channel Hall Effect sensor boards and two 6-pole magnetic discs that can be used to add quadrature encoding to two micro metal gearmotors with extended back shafts (motors and cables are not included with this kit). The encoder board senses the rotation of the magnetic disc and provides a resolution of 12 counts per revolution of the motor shaft when counting both edges of both channels. To compute the counts per revolution of the gearbox output shaft, multiply the gear ratio by 12. This compact encoder solution fits within the 12 mm × 10 mm cross section of the motors on three of the four sides, and it extends 4.2 mm past the edge of the quarter side.

The encoders include a side-entry, 6-pin male JST SH-type connector, and we have cables available for it in three lengths:

• 12 cm (4.5″)
• 30 cm (12″)
• 75 cm (30″)

We also carry a version of this encoder with a top-entry connector; the following pictures show comparisons of the top-entry and side-entry versions:

Note: This sensor system is intended for users comfortable with the physical encoder installation. 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. One way to achieve good alignment between the board and the motor is to tack down the board to one motor pin and to solder the other pin only when the board is flat and 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 connector pins as labelled below, and they can be accessed via the red and black wires when used with our corresponding JST cables. The remaining four connector pins are used to power the sensors and access the two quadrature outputs:

The sensors are powered through the VCC (blue wire) and GND (green wire) pins. VCC can be 2.7 V to 18 V, and the quadrature outputs A and B (yellow and white wires) are digital signals that are either driven low (0 V) by the sensors or pulled to VCC through 10 kΩ pull-up resistors, depending on the applied magnetic field. The sensors’ comparators have built-in hysteresis, which prevents spurious signals in cases where the motor stops near a transition point.

Schematic diagram

This schematic is also available as a downloadable pdf (80k pdf).

Comparison to previous version

This encoder version is a modification of the previous version that adds a connector to enable the use of removable cables. The basic schematic is unchanged, and the electrical performance is identical. The following picture shows the two new encoders with JST SH-type connectors next to the previous (green) one:

Dimensions

General specifications

Identifying markings

Notes:

1

The assembled encoder will extend approximately 5 mm beyond the plastic motor end cap.

2

Weight of full set. Each encoder board weighs ~0.4 g and each magnet disc weighs ~0.3 g.