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Pololu Jrk 21v3 USB Motor Controller with Feedback (Fully Assembled)


Description

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.

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

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. 0–5 V analogue voltage interface for direct connection to potentiometers and analogue joysticks.
  • Two closed-loop feedback options:
    1. 0–5 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 (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 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 – 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

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 0.5"
Weight: 0.23 oz

General specifications

Motor driver: MC33926
Motor channels: 1
Control interface: USB; non-inverted TTL serial;
RC servo pulses; analogue voltage1
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/A2
Maximum PWM frequency: 20 kHz
Minimum logic voltage: 4 V3
Maximum logic voltage: 5 V
Reverse voltage protection?: Y
Partial kit?: N

Notes:

1
Autodetects baud rates between 300 and 115,200 bps, or can be set to any fixed baud rate in this range.
2
Current readings are converted to a digital number from 0-255.
3
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.

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.

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.)

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