Attaching an Encoder to a Stepper motor

The voind robot will use encoders to provide feedback on the position of 4 different axles. These optical encoders attach directly to the motor shaft and were supplied disassembled with the encoder disks carefully packaged inside a sheet of protective foam.


The encoder uses a mylar disk with the optical grid almost invisible to the naked eye. This component attaches directly to the motor shaft.CAM00371_detail

The motor producing the movement on the X direction was the first to have its encoder attached. However, unlike some other motors which already have mounting holes for encoders, this particular motor required an additional arrangement to securely attach the encoder.


An option would be to drill very shallow (2-3mm) mounting holes on the motor backplate hoping that these holes would not damage the motor. However I was not able to determine if the backplate was sufficiently thick to drill a hole without ruining the motor.

The first option was to build a bracket using aluminum sheet that would be secured at the front of the motor using the existing mounting screws and extend to the back of the motor to provide the mounting point for the encoder.


Two bolts would prevent it from moving sideways and provide additional adjustment.


This design had however a fatal flaw: the encoder needs at least 13.5 mm of shaft to properly attach the encoder wheel. This arrangement would let only 8mm of shaft exposed. The part could be redesigned to sit more closely to the motor backplate, giving the extra shaft exposure needed.

We decided to try something simpler: using the very shallow M3 threaded holes on the motor backplate to fix an adapter plate to which the encoder would then be attached. The challenge here was to fix the adapter plate using only 2mm of thread engagement and at the same time providing M3 threaded holes to fix the encoder, all this on 1.8 aluminum sheet.


This arrangement proved to be adequate for fixing the encoder.


After a final cleaning to remove the dust particles that were sitting on the disk, the encoder cover was screwed in.