rotary position sensor

General project help for Adafruit customers

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
jbc
 
Posts: 159
Joined: Wed Aug 14, 2013 7:18 pm

rotary position sensor

Post by jbc »

I have a few stepper motors that use limit switches to set their home position(s).
What I would like to do is use a rotary position sensor that responds to a magnet attached to the stepper motor's shaft so I can know the shaft's position. The limit switch isn't enough as I need to know the angle the shaft is currently placed at.
*******(updated, hopefully making more sense)*******

I came across this while searching for a way for my stepper(s) to know the position of the arm attached to the shaft:
http://www.futureelectronics.com/en/tec ... .aspx?IM=0

I have looked at the hall effect sensor;
https://www.adafruit.com/products/158 and would love to use this as it's small footprint and low cost brings a smile to my face.
I read the white sheet on this item but didn't see it as a solution.

Anyone have a small footprint, low cost rotary position sensor?
Using a magnet on the stepper shaft is a solution I covet.

Thanks in advance for any help.
jbc
Last edited by jbc on Fri Aug 21, 2015 6:24 pm, edited 1 time in total.

User avatar
Franklin97355
 
Posts: 23911
Joined: Mon Apr 21, 2008 2:33 pm

Re: rotary position sensor

Post by Franklin97355 »

Why do you think the hall sensor won't work for you?

User avatar
jbc
 
Posts: 159
Joined: Wed Aug 14, 2013 7:18 pm

Re: rotary position sensor

Post by jbc »

After reading the white paper on the hall sensor it looks to me to function the same as a limit switch....high and low or on and off.
I want to know the position of the stepper's shaft.
Can this hall sensor do that?

User avatar
jbc
 
Posts: 159
Joined: Wed Aug 14, 2013 7:18 pm

Re: rotary position sensor

Post by jbc »

My first post didn't explain what I needed. Sorry. Take a look at what I edited please.

User avatar
Franklin97355
 
Posts: 23911
Joined: Mon Apr 21, 2008 2:33 pm

Re: rotary position sensor

Post by Franklin97355 »

That device would work but you would need to build a board to support it and the electronics to read it. Here is a wiki on encoders. https://en.wikipedia.org/wiki/Rotary_en ... ry_encoder

User avatar
jbc
 
Posts: 159
Joined: Wed Aug 14, 2013 7:18 pm

Re: rotary position sensor

Post by jbc »

Thanks I'll dig in.
jbc

User avatar
jbc
 
Posts: 159
Joined: Wed Aug 14, 2013 7:18 pm

Re: rotary position sensor

Post by jbc »

Franklin, the wiki link describes different processes but does not help with the fabrication.
I will search the web more diligently hoping to find hall effect sensor usage in rotary position sensing.

I was hoping someone here has had success making a low cost approach.
jbc

User avatar
Aridzonan_13
 
Posts: 4
Joined: Tue Dec 29, 2015 1:42 am

Re: rotary position sensor

Post by Aridzonan_13 »

I have worked with hall effect sensor relative encoders. This particular application was on a McDonald Douglas two axial solar tracker. I actually saw one that had been milled by the mechanical rotary element and it still functioned!! However, the down fall to all relative encoders I worked with was you had to "home" them. Where a you have to tell it where "0 deg" is on power up. Absolute encoders are the way to go. I'm going to have to do an experiment with a variable resistor and see what kind of positional resolution I can achieve. Not to mention, check if the R changes with temperature variations.

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: rotary position sensor

Post by adafruit_support_bill »

Robotshop has some reasonably priced optical and magnetic encoders - but they are all quadrature encoders that will give you relative readings. You would need to 'home' them first to get an absolute position..
http://www.robotshop.com/en/encoder-disks.html

Absolute encoders are available also:
http://www.andymark.com/product-p/am-2899.htm
http://www.avagotech.com/products/motio ... -encoders/

Locked
Please be positive and constructive with your questions and comments.

Return to “General Project help”