PWM Control

CTR Electronics motor controllers support "hobby" style 1-2ms rise-to-fall PWM control.

This PWM control is characterized by encoding the applied duty cycle within the 1-2 ms rise-to-fall pulse. A 1.5ms rise-to-fall corresponds to a neutral output, 1ms is full reverse, and 2ms is full forward. Any value between these is an output that linearly corresponds to the output.

In addition to the rise-to-fall parameter, there must be at least 2.9ms and less than 100ms between the rise-to-rise edge.

Note that PWM control is one-way communication and can only set the output duty cycle of the motor controller. Any advanced features the controller has (closed loop control, position reporting, current measurement) would need to be utilized over CAN.

 

Most RC receivers support this style of PWM control, but verify your own RC receiver to ensure this is the case.

Most Arduino Platforms also support the PWM Servo class, in which case you can specify the rise-to-fall period using the "writeMicroseconds()" method. In this case, commanding the motor controller to neutral would be done with "servo.writeMicroseconds(1500)".

PWM Electrical Specifications

The PWM controller is connected by attaching the signal pin to the CAN H (yellow) line, and ground to the CAN L (green) line. Only one set of signal/ground wires is necessary for connection, if the motor controller provides two sets (4 wires total), the other set should be electrically isolated using tape or heat shrink to prevent shorting to itself or the chassis.

The minimum voltage for a logic-high is 1V.

The maximum voltage for a logic-low is 0.4V

PWM Extensions

Our newer Talon motor controllers provide some extensions for configurability over PWM. In every extension case, the specified Rise to Fall period must be sent repeatedly at the previous Rise to Rise rate for at least 1 full second to ensure the configuration is applied.

We recommend updating the device to the latest firmware to ensure it supports extensions listed below. Users may field-upgrade devices over CAN using a CANivore and a Windows computer or through any of our supported platforms.

Brake/Coast

Brake mode can be configured with a Rise to Fall period of 4.0 milliseconds.

Coast mode can be configured with a Rise to Fall period of 3.5 milliseconds.

Motor Arrangement

The Talon FXS requires configuring the motor arrangement for proper control of a motor. The available extensions along with the Rise to Fall timing is provided below:

A Minion can be configured with a Rise to Fall period of 3.0 milliseconds.

A Brushed DC motor can be configured with a Rise to Fall period of 3.7 milliseconds. This allows brushed DC motor control via the A/B (red/black) output terminals.