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Speed Sensor

Introduction

The BAC controller can use various methods of detecting wheel speed. One method is using the Hall or sensorless frequency of the motor. A second method is the internal wheel speed sensor often found in clutched geared direct drive motors or external wheel speed sensors used on mid-drive systems with variable final gear ratios.

This page will guide you through setting up your wheel speed sensor.

Speed sensor input & wiring

Available input sources include: Cruise, Brake 1, Brake 2, Hall A.

Generally, speed sensors are 2-wire and are wired to the input source (pulled up digital input) and to ground.

speed sensor

Speed sensor setup

If you have a direct drive motor, or simply a fixed gear ratio and you want to determine wheel speed without a dedicated wheel speed sensor.

  1. Set the Wheel speed sensor pulses per revolution to 0.
  2. Lastly, set the Wheel diameter.

In this configuration, the controller will use the motor rpm and Gear ratio to determine wheel rpm.

  1. Select the appropriate Wheel speed sensor source.
  2. Enter the Wheel speed sensor pulses per revolution.
  3. If the motor is clutched, for example, enable Motor Features bit 2 Bottom bracket motor to allow for the wheel speed to vary independantly from the motor speed.
  4. Lastly, set the Wheel diameter.
  1. Select the appropriate Wheel speed sensor source.
  2. Enter the Wheel speed sensor pulses per revolution.
  3. Enable Motor Features bit 2 Bottom bracket motor to allow account for the wheel speed ratio to vary independently from the Gear ratio entered in BACDoor® when setting up your motor.
  4. Lastly, set the Wheel diameter.
Troubleshooting

Wheel speed sensor fault - Variable gear ratio system

In variable gear ratio systems, the wheel speed and the motor rpm are not in sync. Enable Motor Features bit 2 Bottom bracket motor, otherwise, the controller will continuously compare wheel RPM (motor based) with wheel RPM (speed sensor based), and if the difference is more than 30 rpm, the controller issues a Warning bit 3 Wheel Speed Sensor and switches to motor-based speed calculation. This fault is latching and will require the controller to be restarted to clear it.

Wheel speed sensor fault - Fixed gear ratio system

In a fixed gear ratio system, if the controller detects a difference of more than 30 rpm between wheel RPM (motor based) and wheel RPM (speed sensor based), it will issue Warning bit 3 Wheel Speed Sensor and switches to motor-based speed calculation. Verify the speed sensor is functioning by watching the appropriate input. Verify the # of motor pole pairs and Gear ratio are correct.