This lower-power, smaller, and lower-cost version of the TReX is the ultimate general-purpose motor controller for small motors: it has a wide operating range (5 to 24 V), delivers 2.5 A continuously per motor, provides current sensing on the two main channels, and it features the TReX triple in...
Pololu TReX Jr bottom with labels and dimensions
The TReX Jr Dual Motor Controller, a lower-power version of the TReX Dual Motor Controller, is a versatile DC motor controller designed to seamlessly blend autonomous and human control of small robots. The TReX Jr can control two bidirectional and one unidirectional motor via three independent control interfaces: radio control (RC) servo pulses, analogue voltage, and asynchronous serial (RS-232 or TTL). Using the compact MC33887 motor driver allows for a single-board design that reduces cost while maintaining a small package. As an added benefit, the use of the MC33887 motor driver allows operation to 24 V.
The TReX Jr uses five input channels to receive the RC or analogue control signals. When operating in RC or analogue mode, the five channels function as follows:
The serial interface can switch instantly with one of the other two interfaces, allowing mixed autonomous and remote control. For example, a robot could be configured to run autonomously most of the time, but a human operator could override the autonomous function if the robot gets stuck or into a dangerous situation. If the serial mode is selected as the primary interface, high-resolution measurements of all five channel input signals (be they RC pulses or analogue voltages) are made available to the autonomous robot controller, allowing for complex and unlimited mixing of operator control and sensor input. For example, the TReX would be a great motor controller for a remotely controlled balancing robot.
Pololu TReX Jr Dual Motor Controller with labels
| Dimensions | 1.75" x 1.75" x 0.5" (0.3" height without connectors) |
| Supply voltage | 5 – 24 V |
| Primary motor outputs | 2 bidirectional, 5 A peak, up to 2.5 A continuous (may be combined to control 1 bidirectional, 5 A continuous) |
| Auxiliary output | 1 unidirectional, 10 A continuous |
| Speed control | 128 steps in each direction |
| Control interfaces | RC servo pulses, analogue voltages, or serial commands; master interface set by mode-select jumper |
| Input channels | 5 (RC servo pulses or analogue voltages) |
| RC pulse measurements | 12-bit resolution, 1 us accuracy |
| Analogue measurements | 10-bit resolution |
| Serial interface | both RS-232 and TTL (logic level), bidirectional |
| Baud rates | supports 11 common baud rates ranging from 1200 to 115,200 bps |
| Expanded protocol | Allows multiple Pololu servo and motor controllers on one serial line |
| Compact protocol | Allows both motors 1 and 2 to be simultaneously set with just three bytes |
Note: The TReX Jr does not require use of the serial interface to function; it will work right out of the box as an electronic speed control (ESC). You will not have access to the full suite of features the TReX Jr provides if you do not make use of the serial interface, though.
24" (600 mm) female-female RC servo extension cable
The TReX Jr has male 0.1" headers; for direct connection to an RC receiver or serial servo controller, we recommend ordering one 6" female-to-female cable, 12" female-to-female cable, or 24" female-to-female cable per channel you intend to use (the TReX Jr can use up to five channels).
| Size: | 1.75" x 1.75" x 0.5" |
|---|---|
| Weight: | 15 g |
| Motor driver: | MC33887 |
|---|---|
| Motor channels: | 31 |
| Control interface: |
non-inverted TTL serial (2-way); RS-232 serial (1-way), RC servo pulses, analogue voltage |
| Minimum operating voltage: | 5 V |
| Maximum operating voltage: | 24 V |
| Continuous output current per channel: | 2.5 A2 |
| Peak output current per channel: | 5 A3 |
| Continuous paralleled output current: | 5 A |
| Current sense: | 0.5 V/A4 |
| Maximum PWM frequency: | 10 kHz |
| Minimum logic voltage: | 2.7 V |
| Maximum logic voltage: | 5.5 V |
| Reverse voltage protection?: | Y |
Sample C# Program for Communicating with the TReX and TReX Jr (Printable PDF)
This sample C# program (written for Microsoft Visual C# 2008) shows how you can use your computer to send and receive data from the TReX and TReX Jr motor controllers.
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