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:
    1. USB interface for direct connection to a PC.
    2. Full-duplex, TTL-level asynchronous serial interface for direct connection to microcontrollers or other embedded controllers.
    3. Hobby radio control (RC) pulse width interface for direct connection to an RC receiver or RC servo controller.
    4. 0–5 V analog voltage interface for direct connection to potentiometers and analog joysticks.
  • Two closed-loop feedback options:
    1. 0–5 V analog voltage.
    2. 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.

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.

TTL serial control.

RC / pulse width control.

Analog control.


Specifications

Dimensions

Size: 1.35" x 1.35" x 0.4"1
Weight: 0.23 oz

General specifications

Motor driver: MC33926
Motor channels: 1
Control interface: USB; non-inverted TTL serial;
RC servo pulses; analog voltage2
Minimum operating voltage: 5 V
Maximum operating voltage: 28 V
Continuous output current per channel: 3 A
Peak output current per channel: 5 A
Current sense: 0.5 V/A3
Maximum PWM frequency: 20 kHz
Minimum logic voltage: 4 V4
Maximum logic voltage: 5 V
Reverse voltage protection?: Y
Partial kit?: Y

Notes:

1
Without included hardware.
2
Autodetects baud rates between 300 and 115,200 bps, or can be set to any fixed baud rate in this range.
3
Current readings are converted to a digital number from 0-255.
4
In RC mode, the pulses can be as low as 2V.

Resources

Documentation and other information

Pololu Jrk USB Motor Controller User’s Guide (Printable PDF)

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 (Printable PDF)

An application note about using AutoHotkey for Windows to control Pololu USB products.


File downloads

Jrk Motor Controller Windows Drivers and Software (release 121204) (5MB zip)
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 (1k txt)
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 (402k pdf)
Pololu Jrk 21v3 USB Motor Controller with Feedback drill guide (60k dxf)
This DXF drawing shows the locations of all of the board’s holes.

(PL-1392)

SKU PL-1392
Brand Pololu

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