Absolute Encoder Mounting


I was wondering if anyone had any pictures on how to attach a absolute encoder to a turning motor, specifically a PG71. I just want to be sure I’m CADing it right. Also, does cad for the abs. encoder exist, it would be nice to incorporate into my CAD.


Here’s the encoder that most people like to use.

To mount it, you use the threads already on it for a low-profile jam nut, which you can use to sandwich the mounting plate. To couple it to anything else, you can use a shaft coupler to the rotating shaft or use a press-on gear, like the Andymark one.


https://www.pololu.com/product/1993 here is a good hub if you want to 3D print a gear for the encoder


Everybody so far has given great responses as to how to actually mount to the encoder shaft, but with regards to coupling the encoder to the turning motor, you actually have a couple of options.

The simplest option is coupling the encoder shaft directly to the shaft that the motor is turning, whether it be by turning down the shaft and using a surgical tubing connector or something more robust. This would typically only work in situations where you have a live axle.

In a situation where you have a dead axle, say, with a motor driving an arm, a good way to make use of the absolute encoder is to have a separate gear reduction just for the encoder that matches whatever reduction you have driving the arm. If you simply just mounted the encoder on the output of the motor, you wouldn’t actually be sensing the movement of the arm!

I hope this made sense! If you have any questions, please don’t hesitate to ask!


Set screws?? I prefer these especially at speeds you’re likely to see on a PG71.


That’s actually a pretty cool find.


An easy way to mount MA3s is to drill out/ream the center of your shaft to 0.25", then cut a small slit into the shaft with a bandsaw. Slide the MA3 in, and use a shaft collar to compress the shaft around the MA3, like a collet. Then use bent polycarb with the integrated nut to secure the body.


What are some best practices for using a potentiometer to measure shaft rotation

When using the surgical tubing method, what connector would you recommend using?


The surgical tubing is the connector. It wraps around the axle shaft (turned down to 1/4") on one side and the encoder shaft (1/4") on the other.

Tested our encoder today that’s mounted like this. For our application, I wasn’t happy with the play it results in when shifting direction, due to the twist of the tubing. Going to see if we can figure out a more rigid coupler.


What did you guys end up using to mount the encoder?


1/4" aluminum spacer, drilled and tapped on either end + set screws (I think #8, but maybe #6). Swore I took a picture, but apparently not. It’s basically what pkrishna3082 posted above. Worked like a charm, but our use is relatively low speed and full travel is about 100 degrees. If you’re using higher speed, I’d go with something like GeeTwo suggested.