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, analogue voltage, and hobby radio control (RC).

AUD$ 104.95

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Discontinued. Replaced by SKU-004772: Jrk G2 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.

Description

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 a lower 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

Pololu Jrk 21v3 USB motor controller with dimensions.

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. Analogue 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 G2 21v3	Jrk G2 18v19	Jrk G2 24v13	Jrk G2 18v27	Jrk G2 24v21
Recommended max operating voltage:	28 V⁽¹⁾	28 V⁽¹⁾	24 V⁽²⁾	34 V⁽³⁾	24 V⁽²⁾	34 V⁽³⁾
Max nominal battery voltage:	24 V	24 V	18 V	28 V	18 V	28 V
Max continuous current (no additional cooling):	2.5 A^*	2.6 A	19 A	13 A	27 A	21 A
USB, TTL serial, Analogue, RC control:
I²C control:
Hardware current limiting:
Dimensions:	1.35″ × 1.35″	1.0″ × 1.2″	1.4″ × 1.2″		1.7″ × 1.2″
Price:	$74.95	$54.95	$109.95	$109.95	$149.95	$149.95

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

Pololu Jrk 21v3 USB motor controller with feedback, labeled top view.

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 analogue voltage interface for direct connection to potentiometers and analogue joysticks.

Two closed-loop feedback options:
1. 0 V to 5 V analogue voltage.
2. Frequency/tachometer digital input up to 2 MHz with 1 ms PID period.
  (Open-loop control with no feedback also available.)

The Input tab of the Jrk Configuration Utility

The Jrk plot window, showing all variables simultaneously.

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 analogue 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 V to 28 V
Continuous output current:	3 A
Peak output current:	5 A
Auto-detect baud rate range:	300 bps to 115,200 bps
Available fixed baud rates:	300 bps to 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

Pololu Jrk 21v3 USB motor controller with included hardware soldered in (fully assembled).

Pololu Jrk 21v3 USB motor controller with 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; analogue 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
Version:	original 21v3 (28 V max, 3 A max continuous)

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)
3D model of the Pololu Jrk 21v3 USB Motor Controller with Feedback (10MB step)
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.

FAQs

Why is the Jrk not driving my motor?: There might be an error preventing the Jrk from driving the motor; check the Errors tab in the configuration utility. If you are trying to use a feedback mode, make sure that you have entered some non-zero PID constants (good starting values are Proportional=1, Integral=0, Derivative=0) and make sure there is a large difference between the values of the Target and Feedback variables. If you are trying to use the no-feedback (speed control) mode, then make sure that the target is not close to 2048 (speed 0); try setting the target to 2648 (full speed forward). In either case, you should look at the graph and make sure that the Duty Cycle is not close to 0; try to get it closer to +600 or -600 (full speed forward or full speed reverse).
Does the Jrk support using a quadrature encoder for feedback?: The Jrk motor controllers do not work with encoders, in the sense that you cannot get position control over unlimited number of rotations. (The Jrks are typically used with potentiometer feedback, which allows for up to a few rotations when using multi-turn potentiometers.)