Author Topic: Connecting an absolute encoder to a 1 1/4" diameter shaft  (Read 1368 times)

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Offline cadcoke5Topic starter

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Connecting an absolute encoder to a 1 1/4" diameter shaft
« on: May 10, 2016, 01:53:16 PM »
I am designing a robot for industrial use.  I am currently using a worm drive gearbox that drives the rotation using a V-belt system.  To permit the end user to disengage the drive mechanism, and move the equipment by hand, there is a clutch-like mechanism that adjusts tension on the V-belt. So, when the v-belt is slack, they can move it by hand.

However, this design also means that the encoder I have on the motor is not going to help me after the user has made use of the clutch.  So, I need an encoder on the main shaft of the equipment.  Currently, I have a 5-sensor Single Track Grey Code system that gives me 12deg of resolution. https://en.wikipedia.org/wiki/Gray_code#Single-track_Gray_code

However, ideally I would like much better resolution.  So, I am trying to work a commercial absolute encoder into the system. I have a hollow shaft that is 1 1/4" Dia, and a solid shaft that is 2" Dia.  Here is one that can adapt to various shafts, http://www.mouser.com/ds/2/670/amt20-534922.pdf
But, its max is an 8mm shaft.  And since my 1 1/4" Dia. shaft is hollow to allow for wiring to go though, I can't just make a adapter at the end.

So, I think I need to use a timing belt connection to tie the large shaft to the small shaft of an encoder.  But, this is proving to be a challenge as well.  The timing belt pulleys I find, that are for narrow belts, do not come with large bore sizes.  At Martin Sprocket, their timing belt pulleys that can handle my Shafts are for 1/2" belts, and the pulley is 1 3/8" Thick. I don't have much space to fit this, and this is a bit tight for my space.  I also would prefer a thinner belt, so hopefully my encoder can just take the pulley without any special effort to support the force of the belt and weight of the pulley.

Any suggestions for a source for timing belt pulleys for narrow belts, but for up to a 2" dia shaft? Or alternatively, a different method of putting an encoder on a shaft, but not on the end?

Thanks for any ideas,
-Joe

Offline bdeuell

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Re: Connecting an absolute encoder to a 1 1/4" diameter shaft
« Reply #1 on: May 10, 2016, 07:46:59 PM »
Drawings and/or photos of your existing setup would help.

It will probably be hard to find a narrow (i'm guessing you are thinking ~1/4") timing belt pulley with a 2" bore. You may need to modify or otherwise manufacture a custom pulley to go this route.

 


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