Jrk 21v3 USB Motor Controller with Feedback

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 V to 28 V, with derated performance down to 5 V and transient protection to 40 V. This version ships with connectors included but not soldered in, allowing for custom installations.

Not recommended for new designs: We strongly recommend our newer and better (and smaller) Jrk G2 21v3 USB Motor Controller with Feedback over this controller, as it offers increased power and many other improvements at the same price. We are continuing to offer the original Jrk 21v3 for now as a legacy product for those with systems designed specifically for this controller.

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. A USB A to mini-B cable (not included) is required to connect this controller to a computer.

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.

The table below lists the members of the Jrk family, including the original (green) and newer G2 (black) versions, and shows the key differences among them.

	Jrk 21v3	Jrk 12v12	Jrk G2 21v3	Jrk G2 18v19	Jrk G2 24v13	Jrk G2 18v27	Jrk G2 24v21
Recommended max operating voltage:	28 V(1)	16 V	28 V(1)	24 V(2)	34 V(3)	24 V(2)	34 V(3)
Max nominal battery voltage:	24 V	12 V	24 V	18 V	28 V	18 V	28 V
Max continuous current (no additional cooling):	2.5 A*	12 A	2.6 A	19 A	13 A	27 A	21 A
USB, TTL serial, Analog, RC control:
I²C control:
Hardware current limiting:
Dimensions:	1.35″ × 1.35″	1.85″ × 1.35″	1.0″ × 1.2″	1.4″ × 1.2″		1.7″ × 1.2″
Price:	$79.95	$199.95	$59.95	$119.95	$119.95	$149.95	$159.95
1 Transient operation (< 500 ms) up to 40 V. 2 30 V absolute max. 3 40 V absolute max. * Reduced from “3 A” based on newer, more stringent tests. The value now is directly comparable to the rating for the newer G2 21v3.

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 V to 5 V analog voltage interface for direct connection to potentiometers and analog joysticks.

• Two closed-loop feedback options:
  1. 0 V to 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 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

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.