Like the Jrk 12v12, the JRK 21v3 is a very well thought-out motor controller. It's like a little brother - similar characteristics, but not quite as strong. It's ideal for small motors. Nice work, Pololu!

Where the 12v12 is rated 16V and 12A continuous output, the 21v3 is rated 28V and  3A. Almost every other feature of the 12v12 implemented in the 21v3 (the exception being the current sensor being 0.5V per amp).

Main points of interest:

• 5 to 28 VDC power input
• 3A with 5A surge current rating
• Can be controlled via:
  • USB
  • PWM (servo remote control style)
  • Analog joystick/potentiometer
• Optional Feedback control via:
  • 0-5V analog input
  • Frequency signal (like a tachometer)
• Calibrate with USB interface to Windows software
• Configure feedback loops via software with control over
  • PID period & constants. (Proportional / Integral / Derivative - embedded!)
  • Error response
  • Learning calibration for RC / Analog interfaces
  • Programmable maximum
    • Current
    • Duty cycle
    • Acceleration

WOW - that's a huge bundle of features for a compact unit measuring only 1.35" x 1.35" x 0.4"!

So what make is so superior to other models of motor driver units?

• Control the motor via a PC's USB port (as simulated serial interface)
• Ultrasonic PWM to eliminate switching-induced motor shaft hum or whine.
• Robust, high-speed communication protocol with user-configurable error condition response.
• 12-bit resolution (that's 4096 levels) for smooth and flexible calibration to various input and feedback devices.
• Current sensing and limiting.
• Reversed power protection.
• Field-upgradeable firmware.

The only serious limit to this unit is that it is a single motor driver. Not dual. So if you want to drive a robot, you'll need one of these per motor. But with this feature set, it'll be very easy to work with!

Specifications:

Included Hardware:

The jrk ships with a 14×1 straight 0.100" male header strip and two 5mm, 2-pin terminal blocks. To provide maximum flexibility, none of these parts are soldered to the board.

For the most compact installation, you can solder wires directly to the jrk pads themselves and skip using the included hardware. The included hardware allows you to make less permanent connections. You can break the 14×1 header strip into an 8×1 piece and two 3×1 pieces and solder these strips into the jrk’s I/O pads.

Note: USB cable not included.

• [Documentation]: Pololu Jrk USB Motor Controller User's Guide
• [Support Software]: Drivers & Config Utility for JRK 21v3 and 12v12