Hall effect sensors

[Omiccioli]

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

[PAPPP]

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]

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

[WillAdams]

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

[calebv2]

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

[Omiccioli]

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]

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]

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.

[Omiccioli]

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]

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.