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 7, Vista, or Windows XP) 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 (Windows 7, Vista, and Windows XP compatible).
- 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 14×1 straight 0.100" 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.
Example Feedback System – 4 Methods of Control
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| 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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Documentation and other information
Pololu USB Software Development Kit
The Pololu USB SDK contains the code you need for making your own applications that use native USB to control the Jrk Motor Controller, Maestro Servo Controller, Simple Motor Controller, or USB AVR Programmer.
Recommended links
- The Haunted Organist
- A spooky animatronic skeleton using the Jrk USB Motor Controller. See the final result or more pictures and information. By Mark Goodson, October 2009.
- R2D2 dome position control
- A replica of the famous Star Wars droid R2D2 that uses the Jrk USB Motor Controller for position control. See the video which shows the Jrk Configuration Utility in action, or read the blog post which has more information. By ggpipe, February 2010.
- Microsoft .NET Framework 3.5
- The Microsoft .NET Framework version 3.5 is required for many Pololu configuration, control, and utility programs under Windows. Most computers will have this installed already or can automatically install it over the internet, but you can also get .NET 3.5 directly from Microsoft at this link. If you are installing on a computer without internet access, make sure to get the Full Redistributable Package.