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Massmind.org Abosolute/Incremental Rotary Encoder

Commercialy available, partially assembled low cost encoder module

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This moudule is based on the AS5134 magnetic encoder IC, good for up to 76,875 RPM and 360 count per revolution (with 4x decoding). It senses the position of a two pole radially magnetized disk over a full revolution using a hall effect sensor array. The sensor signal changes are converted to a digital quadrature signal, and the position information stored as absolute position data on some registers, which are readable through a 3 wire synchronous serial interface.

Available for purchase on http://techref.massmind.org/techref/io/sensor/pos/enc/ENC1.htm

http://techref.massmind.org/techref/io/sensor/pos/enc/ENC1.htm
Based on the amazing AS5134 chip, this encoder supports 76875 RPM, 360

CPR/counts per revolution (with 4x decoding) quadrature rotational

encoding. It senses the position of a two pole radially magnetized disk

over a full revolution using a hall effect sensor array. The sensor

signal changes are converted to a digital quadrature signal, and the

position information stored as absolute position data on some registers,

which are readable through a 3 wire synchronous serial interface.

Standard quadrature Index, A and B phase signals are also generated just

like any standard encoder.

  • 76,875 RPM (!!!)
  • Non-contact magnetic sensor.
    • No need to mechanically attach to a shaft, just epoxy a small magnet in place. Great for motors with one shaft.
    • Alignment isn't critical. As long as the magnetic field is generally over the chip, within 1/2 inch, it will work quite well
  • The onboard LED indicates that the board is powered, and provides easy testing the alignment of the IC with respect to the magnet.
  • Multiple connection / cable options are supported.
  • Standard Quadrature A and B phase outputs, as well as several digital modes.

Limitations:
  • Fairly low resolution: 360 positions per revolution (1 degree). Honestly, that just helps the PID controller manage higher RPMs. For most applications 360 is plenty. Steppers are 200 to 400 in the real world, as microstepping is NOT positionally accurate.

sch - 395.05 kB - 08/23/2016 at 22:54

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Adobe Portable Document Format - 3.27 MB - 06/03/2016 at 23:33

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sch - 360.77 kB - 06/03/2016 at 23:30

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  • Circular form factor by Bogdan Fargas

    ottoragam08/23/2016 at 22:54 0 comments

    I got an email from Mr. Bogdan Fargas informing me of his modified AS5134 PCB. He needs to control a GR63x25 DC motor from Dunkermotoren for a coil winding machine. He wanted to stack the motor, the encoder board and servo drive board, so he created a circular PCB version of said boards.

    I've been given permission to post his files here. Hopefully they'll be of use to some of you!

View project log

  • 1
    Step 1

    Connector Options / Assembly

    The board supports multiple connector types:

    PMinMO: A 2x5 header soldered on the edge with the PCB inserted between the pins which are soldered along the face of the pads. Used with a 10 conductor ribbon cable and IDC female 2x5 connector, this option has the advantage of a ground line between each signal for very low noise and long runs.

    To install a PMinMO shrouded header, align pin one (marked with the triangle on the shroud) with the pin marked "INDEX" on the edge of the PCB, with one row of pins along the top surface mount pads, and the other row along the bottom pads (see picture below). The notch in the shroud should be on the top side of the PCB, where the chip is mounted. Solder a single pin, then check alignment and solder on the rest. To avoid overheating the plastic and warping the pin positions, solder one pin on the top, then the opposite pin on the bottom, alternating back and forth. It also helps to have a female IDC connector cable plugged into the header while soldering.

    Single Row: A Molex KK or 1x5 header soldered through hole can also be used. In this case, it is best to use a polarized header and cable so that it can not be plugged in backwards.

    Bare Wires: Or you can just solder the wires directly into the holes. Some strain relief, such as threading the wires through an unused mounting hole, would be wise.

    Installation

    Magnet:

    Attach the magnet disk to the part where you need to sense angular position, e. g. front or back of the motor shaft, lead screw, ball screw, etc. For testing and alignment, the magnet will stick to any steel shaft, but vibration and shock will dislodge it. A two part epoxy is recommended for a permanent mounting. After affixing the magnet, slowly turn the shaft to ensure it is centered and will not vibrate loose at higher speeds.

    Mounting:

    The board must be mounted so that the chip is close (less than a half inch) to the magnet and centered over the magnet’s axis of rotation.

    The board supports M3 and #4 screws. At least two screws (diagonally) should be used to hold it in position. Three screws are best. Click the picture to right for a detailed mounting diagram.

    Turn the shaft where the magnet is attached. If the board is centered and close enough to the magnet, the onboard LED should dim and brighten as the magnet rotates in front of the IC.

    Operation

    A microcontroller, such as the Microchip PIC (as used on our BOB PID controller) or ATmega328p (Arduino Uno, Arduino Nano, several other Arduino variants), should be present to read the STEP/DIR signals from the machine controller, read a quadrature encoder input and perform the calculations required for a PID control of the motor position. For more on General PID theory see
    http://www.cds.caltech.edu/~murray/books/AM05/pdf/am08-complete_22Feb09.pdf

    The PID controller, such as the MassMind BOB PID will need to be tuned.

View all instructions

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