Hall effect sensors

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Omiccioli
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Re: Hall effect sensors

Post by Omiccioli » Thu May 07, 2015 1:52 am

I noticed and I tried it myself. Was nervous at first but then I saw how well it worked I was able to relax. :D

PAPPP
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Re: Hall effect sensors

Post by PAPPP » Thu May 07, 2015 8:04 pm

I've been using bare A3144 type sensors for about two years and really like them. Installed on the ends of servo extension cables for convenient wiring, using little rare earth disc magnets taped to the extrusion to trigger. They only cost about $1.70/ea including the servo cables and such. No built-in indicator, but if the machine is powered and under control, there is something to observe them with in software at the other end.

The only annoying bit is arranging to get power to them, since most boards are really only set up for sense and ground.

atrueresistance
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Re: Hall effect sensors

Post by atrueresistance » Thu May 07, 2015 9:57 pm

Is there a clear difference between types of sensors? Optical, Switch, or Hall Effect?
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WillAdams
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Re: Hall effect sensors

Post by WillAdams » Thu May 07, 2015 11:53 pm

AIUI optical are vulnerable to dust, mechanical to vagaries of mechanical accuracy, Hall effect are more expensive.
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calebv2
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Re: Hall effect sensors

Post by calebv2 » Fri May 08, 2015 3:14 am

Hall effect are more expensive because you getting a more accurate and much better product.

Omiccioli
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Re: Hall effect sensors

Post by Omiccioli » Fri May 08, 2015 9:45 am

In addition, you can control the effects of the Hall sensor by changing parameters such as voltage, placement, strength and orientation of the magnets. Where as a optical sensor is more rigid in the deployment.

LTEPM
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Re: Hall effect sensors

Post by LTEPM » Fri May 08, 2015 12:21 pm

Has anyone preformed a test to see how repeatable the stops are and if they are consistent? I like the idea of the sensors, but would like a comparison of repeatability accuracy compared to mechanical switches.

WillAdams
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Re: Hall effect sensors

Post by WillAdams » Fri May 08, 2015 12:39 pm

FWIW, we did have a note on the wiki about this:

http://www.shapeoko.com/wiki/index.php/ ... t_Switches
Limit switches can be mechanical, magnetic, optical, or a combination. There are pros and cons to each. For example, mechanical are the easiest to setup, test, and adjust; but they are also physically moved and therefore can fail or get in the way. Optical sensors don't require contact so the potential for damage is reduced, but calibration can be difficult. Dust and dirt can degrade reliability run-after-run. Magnetic sensors, such as Hall Effect sensors, are a great option as they only need to be calibrated once and are very reliable even if dirty. But you must do your research on the components and some coding may be required.
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Omiccioli
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Re: Hall effect sensors

Post by Omiccioli » Fri May 08, 2015 12:48 pm

I don't have measuring tools but I have an idea of repeatability that I am going to try. I'm on a business trip so I will attempt it this weekend and report on it.

jjubenv
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Re: Hall effect sensors

Post by jjubenv » Sat May 09, 2015 1:52 pm

There is a large thread in a cnczone forum about Hall Effect sensors (http://www.cnczone.com/forums/open-sour ... forum.html). About 8 posts down, he shows some of the repeatability of them, they are pretty accurate.

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