Overview
The jrk 21v3 is a versatile, general-purpose motor controller that supports a variety of interfaces, including USB. The broad operating range from 5 V to 28 V and continuous output current of 3 A (5 A peak) allow this board to control most small DC brushed motors. Analog voltage and tachometer (frequency) feedback options allow quick implementation of closed-loop servo systems, and a free configuration utility (for Windows) allows easy calibration and configuration through the USB port.
Key improvements over competing products and earlier Pololu motor controllers with feedback include:
- USB connectivity with emulated serial (COM) port allows direct motor control from a PC.
- Ultrasonic PWM to eliminate switching-induced motor shaft hum or whine.
- Robust, high-speed communication protocol with user-configurable error condition response.
- High internal resolution (12 bits) for smooth and flexible calibration to various input and feedback devices.
- Current sensing and limiting.
- Reversed power protection.
- Field-upgradeable firmware.
Note: A USB A to mini-B cable (not included) is required to connect this controller to a computer.
Main Features of the Jrk 21v3
- Simple bidirectional control of one DC brush motor.
- 5 V to 28 V operating supply range.
- 3 A maximum continuous current output (5 A peak).
- Four communication or control options:
- USB interface for direct connection to a PC.
- Full-duplex, TTL-level asynchronous serial interface for direct connection to microcontrollers or other embedded controllers.
- Hobby radio control (RC) pulse width interface for direct connection to an RC receiver or RC servo controller.
- 0–5 V analog voltage interface for direct connection to potentiometers and analog joysticks.
- Two closed-loop feedback options:
- 0–5 V analog voltage.
- Frequency/tachometer digital input up to 2 MHz with 1 ms PID period.
(Open-loop control with no feedback also available.)
- Simple configuration and calibration over USB with free configuration program for Windows.
- Configurable parameters include:
- PID period and PID constants (feedback tuning parameters).
- Maximum current.
- Maximum duty cycle.
- Maximum acceleration.
- Error response.
- Input calibration (learning) for analog and RC control.
- Optional CRC error detection eliminates communication errors caused by noise or software faults.
- Reversed power protection.
- Field-upgradeable firmware.
- Optional feedback potentiometer disconnect detection.
- Comprehensive user’s guide.
Specifications
| Motor channels: |
1 |
| Operating voltage: |
5 – 28 V |
| Continuous output current: |
3 A |
| Peak output current: |
5 A |
| Auto-detect baud rate range: |
300 – 115,200 bps |
| Available fixed baud rates: |
300 – 115,200 bps |
| Available PWM frequencies: |
20 kHz, 5 kHz |
| Reverse voltage protection?: |
Yes |
| USB connector style: |
USB Mini-B |
The jrk 21v3 is the smaller of two jrk motor controllers. For a higher-power version, see the jrk 12v12.
Included Hardware
The jrk 21v3 is available in two versions: “fully assembled” with terminal blocks and 0.1″ male header pins pre-installed (left picture above), and connector-free (right picture above). The connector-free version includes a straight 0.1″ breakaway male header strip and two 3.5mm, 2-pin terminal blocks, but these parts are not soldered to the board, which allows for custom installations.
The three mounting holes are intended for use with #2 screws (not included).
Example Feedback System – 4 Methods of Control
USB control. |
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TTL serial control. |
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RC / pulse width control. |
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Analog control. |
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