Pololu TReX Dual Motor Controller DMC01

The TReX blends RC, analogue, and serial inputs for a powerful motor control solution capable of delivering a continuous 13 A per motor.

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Our Code: SKU-002408

Supplier Link: [Pololu MPN:777]

Description

A Novel Blend of Serial, RC, and Analogue Motor Control

The TReX Dual-Motor Controller is a versatile, high-power DC motor controller designed to seamlessly blend autonomous and human control of small- and medium-sized robots. The TReX 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). It maintains compactness through a two-board design that features the VNH2SP30-based Dual High-Current Motor Driver Carrier as its bottom layer. (For a lower-power version of the TReX, please consider the TReX Jr).

The TReX 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:

Channel 1: motor 1 speed and direction or, if in mix mode, turn left/right
Channel 2: motor 2 speed and direction or, if in mix mode, go forward/reverse
Channel 3: auxiliary (unidirectional) motor speed
Channel 4: can be used to enable “flipped mode”, which allows invertable robots to be controlled as normal when they are inverted
Channel 5: determines whether the motors are controlled by the channel inputs or the serial interface; this channel allows you to switch between autonomous and human control at will

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 Dual Motor Controller with labels

Technical specifications

Dimensions	1.9" x 1.9" x 0.8"
Supply voltage	6 – 16 V
Primary motor outputs	2 bidirectional, 30 A peak, up to 13 A continuous per channel (may be combined to control 1 bidirectional, 25 A continuous)
Auxiliary output	1 unidirectional, 15 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

RC/Analogue control features

Battery Elimination Circuit (BEC) jumper lets the TReX optionally power your RC receiver or analogue controller
mix-mode jumper allows for single-stick motor control of differential-drive robots
automatic calibration for your particular RC or analogue controller (the TReX can learn the channel ranges)

Options accessable through the serial interface

all five high-resolution channel input values are available
remapped channel input values show what the TReX would do if it were in control
optional 7-bit cyclic redundancy checking to ensure command/data validity
calibration values can be explicitly read and set
each channel can be reversed and parabolically scaled
current limit, acceleration, and maximum motor speed settings
the bidirectional motors can (individually) be set to coast or variable brake when in the deadband
upgradable firmware

Safety features

“safe-start” requirements prevent accidental motor activation at power-up
optional automatic motor shutdown on serial error, timeout, or input channel noise

Note: The TReX 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 provides if you do not make use of the serial interface, though.

Pololu TReX connected to an RC receiver

Servo cable accessories

The TReX 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 can use up to five channels).

Specifications

Dimensions

Size:	1.9" x 1.9" x 0.8"
Weight:	1.3 oz

General specifications

Motor driver:	VNH2SP30
Motor channels:	3¹
Control interface:	non-inverted TTL serial (2-way); RS-232 serial (1-way), RC servo pulses, analogue voltage
Minimum operating voltage:	6 V
Maximum operating voltage:	16 V
Continuous output current per channel:	13 A
Continuous paralleled output current:	25 A
Current sense:	0.13 V/A²
Maximum PWM frequency:	19.5 kHz
Minimum logic voltage:	2.7 V
Maximum logic voltage:	5.5 V
Reverse voltage protection?:	Y

Notes:

1: Two bidirectional, one unidirectional.
2: Current readings are converted to a digital number from 0-255.

Resources

Documentation and other information

Pololu TReX User’s Guide (Printable PDF)

User’s guide for the Pololu TReX motor controller

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.

File downloads

TReX Configurator utility for Windows version 100608 (295k zip): If you have the ability to connect your TReX to a computer (via serial port or USB-to-serial adaptor), you can use this program to monitor the channel inputs, control the motor drivers, and configure its various settings. This version supports TReX and TReX Jr firmware versions 1.3 and below. Please manually uninstall older versions of the TReX Configurator before installing this version.
TReX command documentation (100k pdf)
TReX configuration parameter documentation (125k pdf)
TReX (DMC01) Firmware version 1.2 (160k trx): This firmware fixes a bug that affected the 38,400 and 28,800 bps baud rates, and it adds a configuration parameter that lets you optionally insert a 1 ms delay between the last byte of a received command packet and the first byte of the TReX’s transmitted response. Without this delay, slower controllers, such as the Basic Stamp, can miss the first byte of the TReX’s response.
VNH2SP30 motor driver datasheet (670k pdf)
Drill guide for Pololu TReX Dual Motor Controller DMC01 top board (113k dxf): This DXF drawing shows the locations of all of the board’s holes. The DXF for the bottom layer can be found on the product page for the Dual VNH2SP30 Motor Driver Carrier MD03A.

FAQs

Why can’t I get the TReX or TReX Jr to work at 28.8 or 38.4 kbps baud rates?: TReX and TReX Jr firmware versions 1.0 and 1.1 have a bug that prevents the device from working at 28,800 and 38,400 bps baud rates. All other supported baud rates work correctly on versions 1.0 and 1.1, so if you do not need them, there is no need to perform a firmware update. Firmware version 1.2 fixes this bug. You can find this firmware update under the resources tab of the product’s web page. Note that you should also upgrade to TReX Configurator version 090923 or later before you perform the firmware update (you will need to manually uninstall any earlier versions of the TReX Configurator). Please see the product user’s guide for instructions on performing a firmware update.