Optoelectrical Rotary Quadrature Encoder Disc and Sensor Mount
Description
IMPORTANT: This is work in progress. This is my first take on a rotary quadrature encoder, customized for Mr Baddeley's R2D2 v2 design (https://www.thingiverse.com/mrbaddeley/about), using scooter E100 motors and the mod I shared here: https://www.thingiverse.com/thing:3356464 It is intended to allow for accurate measurement of the motor's movements, using low-cost sensors and ICs, paired with an Arduino microcontroller. It is important the sensor case and the encoder disc to be printed in BLACK, so that any stray light is not as easily reflected. The backing of the disc should be printed in WHITE (see below). Encoder Disc The encoder disc should be printed in two colors: black for the front side (with the slots) and white for the back side (which reflects the light). The two parts should easily slide into each other. You can also use aluminium foil/tape between the two parts, to increase reflectivity as in the photo, but I found the use of plain white plastic to give much more reliable to results (diffusses the light). The encoder disc is inserted over the motor's spacer, behind the motor's sprocket. Make sure it's about 1mm away from the motor's front cover and doesn't rub when the motor rotates. Sensor Assembly To assemble the sensor, insert 3x RPR220 reflective sensors into the corresponding slots. Each sensor has 4 pins, which should be guided through the holes at the back of the casing. Also, insert 2x M3 square nuts into the corresponding slots. The assembly is bolted on the side of the motor, with the sensors facing the three tracks of the encoder disc. You will need 2x M3 countersunk bolts, 8mm long. Currently, installation requires drilling the plastic bracket (that holds the motor) with a rotary tool, as in the photo. The holes should form a 52 degrees angle from the motor's shaft. It helps drilling two pairs of holes, at different heights, then working your way to merge each pair into a slot. This will allow you to adjust the distance of the sensors from the encoder disc. Updates: * 09 Feb 2019: Updated the description. The circuit has now been tested at speeds up to 27km/h and delivers motion events with 100% accuracy. After these results, I can't expect anything better :-) * 05 Feb 2019: Updated the encoder disk, the sensors assembly, the circuit and the firmware. Huge improvement in accuracy. * 04 Feb 2019: Encoder Disc: Improved the design of the encoder disc (for accuracy) and switched to 24 slots per track. The electronics have been designed, prototyped and tested at slow speeds. My TO-DO List: - Design a PCB for the circuit. - Update this thing with complete instructions. - Design a protective cover that clips over the wires.
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