The jrk 21v3 motor controller is a highly configurable brushed DC motor controller that supports four interface modes: USB, logic-level serial, analog voltage, and hobby radio control (RC). The controller can be used with feedback for closed-loop speed or position control, or it can be used without feedback as an open-loop speed control. The continuous output current is approximately 3 A in the recommended operating range of 8–28 V, with derated performance down to 5 V and transient protection to 40 V. The board ships with connectors included but not soldered in, allowing for custom installations.
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 (Windows 8, 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.
- 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.
The jrk 21v3 is available in two versions: “fully assembled” with terminal blocks and 0.1 male header pins pre-installed, and this connector-free version. 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
- TTL serial control
- RC / pulse width control
- Analog control
- Product Wiki
- Pololu Jrk USB Motor Controller User’s Guide: The user’s guide for the Jrk 21v3 USB Motor Controller and the Jrk 12v12 USB Motor Controller.
- Pololu USB Software Development Kit: The Pololu USB SDK contains example code 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.
- Application Note: Using AutoHotkey with Pololu USB Products: An application note about using AutoHotkey for Windows to control Pololu USB products.
- Jrk Motor Controller Windows Drivers and Software (release 121204): This ZIP archive contains the installation files for the Jrk Configuration Utility, the jrk command-line utility (JrkCmd), and the jrk drivers for Microsoft Windows.
- jrk 21v3 settings for linear actuators: Use a jrk 21v3 to precisely control our Concentric LD series linear actuators with feedback. Instructions for using this file can be found on the linear actuator product pages.
- Dimension diagram of the Pololu Jrk 21v3 USB Motor Controller with Feedback
- Pololu Jrk 21v3 USB Motor Controller with Feedback drill guide: This DXF drawing shows the locations of all of the board’s holes.
- 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.
- VertiGo robot drives up walls with propellers: VertiGo is a novel robot designed with one main goal: the ability to drive on floors and walls, even if the walls arenât perfectly flat. To...
- Raspberry Pi-controlled chicken coop: Forum user bennard posted about his WiFi-enabled chicken coop, which uses a Raspberry Pi to monitor and log data about its environment, serve a web...
- Maker Faire demo: automated treasure chest with jrk motor controller and linear actuator: This blog post is part of a continuing series of blogs about the demos that Pololu displayed at our booth at Las Vegas Mini Maker Faire 2014. For...
Jrk 21v3 USB Motor Controller with Feedback 
- Brand: Pololu
- Product Code: POL-1392
- Reward Points: 43
- Availability: 1
- Ex Tax: £43.95
- Price in reward points: 500