Magnetic Encoders

WHERE IT'S USEFUL
01 Mechatronics 12-bit magnetic encoder breakout board allows you to measure absolute angle of a continuous servo. Servos come with position control, but they are not able to rotate more than 180 - 270 degrees without being "hacked" (having the internal potentiometer removed). Once a servo is hacked, it can no longer provide position feedback. If you need both continuous rotation and position feedback a servo alone will not be sufficient. For example, almost any walking robot will need position feedback in order to coordinate the legs. If the drive motors for the legs continually rotate (instead of rotating back and forth which depends on the mechanical design), position control over continuous rotation will be needed. In this case the 01 mechatronics magnetic encoder will be very effective.

BASIC THEORY:
A permanent magnet is glued on the end of the rotating shaft, and the breakout board is mounted with the top facing the end of the rotating shaft within a few millimeters. Hall effect sensors and a lot of digital signal processing in the IC chip allow the angular position of the magnet (and, hence, the angular position of the rotating shaft), to be calculated. The Pulse Width Modulation (PWM) option sends out a square wave signal with a duty cycle proportional to the angle. A simple 2nd order low pass filter can be used to filter out the average value of the signal, and then this can be read through an analog input on a microcontroller.

PRODUCT INFORMATION:
The product comes mounted on a small 15mmx15mm PCB and includes a circular magnet. Instructions for installation into a standard servo are on the 01 Mechatronics website. You can also request them to install the product into a servo of your liking for a fee of 5 to 10 dollars.

WHERE TO ORDER:
Here is a link to the product on their website:


 * http://www.01mech.com/MagEnc