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Author Topic: Limit switch wiring advice needed from you electronics guys, please!  (Read 7770 times)

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Offline simpson36

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Getting false estops again. First time it was swarf getting on switch contacts. Easily remedied. Now getting spooky random e-stops for no apparent reason.

One cause could be momentary induction on the 5v limit switch wires, so I read that bumping them to 24v is the solution . . again easy enough.

I'm at 'Electronics for Dummies' level, so I need some help interfacing the new 24v daisy chain back to the breakout without frying things . . . . again   :'(.

So I would appreciate getting some advice on two possible solutions. First, a part number and wiring instructions for an optoisolator to connect the 24v limit switch loop to the breakout.

Second, I replaced a broken limit switch (don't ask   :-[) with a Cherry brand and it is very inconsistent on homing. I would like to replace all of the mechanical switches with something like the NTE3100 photointerruptor. Would that be a good choice and how would one go about building a circuit out of three of those daisy chained back to the breakout?

Thanks!

BClemens

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #1 on: April 20, 2009, 07:28:24 AM »
During the initial set-up of this machine, I had a similar experience - random Estops for no apparent reason. These turned out to be sourced from the computer. My daughter had borrowed this book sized computer during my speedy conversion of this machine and she had installed a printer for some writings she was doing. The printer was no longer there but the signal from the driver was. That was causing the estops here - may look into that.....

Bill C.

Also, mechanical switches vary very much with quality and their 'snap action' may be inconsistent. But, I personally would rather have a good mechanical limit switch than any photo or magnetic (hall effect, etc) proximity or whatever. Like a steam locomotive - easy to see what the problem is and fix. I enjoy electronics, work with it daily but in this application, simplicity wins. Stay with the mechanical switches.
« Last Edit: April 20, 2009, 07:40:38 AM by BClemens »

Offline simpson36

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #2 on: April 20, 2009, 09:47:10 AM »
I am aware of the printer driver problem. There is no driver installed, and the mother board is a very high quality server board. The driver test provided with mach is a dead flat line up to 65khz.

When I was getting chips on the switches, I could see the problem clearly on the diagnostics screen, but now there are no clues, so it's going to be difficult to track down a cause for the random e-stops.

So it seems like it is down to eliminating possible causes, one of which, the consensus is, would be running the limit switches at 5v.

Is there a particular brand of mechanical switches that are considered particularly accurate?

 

Offline Greolt

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #3 on: April 20, 2009, 10:02:06 AM »
Not that you should not do all those things you mentioned but.....

Put the debounce interval up to about 5000 and see what happens.

Greg

Offline simpson36

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #4 on: April 21, 2009, 04:32:34 AM »
Thanks Greg, I'll give that a try.

Still I would like to convert to optical interruptors for accuracy so if anyone can help out with a schematic, that would be great.

I only know the very basics when it somes to electronics, but it seems a circuit design like I'm seeking should be a piece of cake for the electron guys. Maybe it is more complicated that I think.

I'm testing a new design breakout board and speed controller from Peter Homann and I also asked him if I can interface photointerruptors. He responded "oh sure no problem, very straightforward . . . a resistor and a diode" . . .

So I asked if he could provide an  'Electronics for Dummies' version of the answer . . with numbers and drawings of wire and stuff like that . .  :-[

BClemens

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #5 on: April 21, 2009, 07:46:03 AM »
Cannot seem to post the diagram...page goes blank. Something amiss?

Simpson, I'll try to post your diagram later today - again.

Bill C.

BClemens

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #6 on: April 21, 2009, 11:56:24 AM »
Simpson,

Here's a diagram, hope this helps. (The correct topic this time!)

Bill C.

BClemens

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Re: Limit switch wiring advice needed from you electronics guys, please!
« Reply #7 on: April 21, 2009, 12:08:36 PM »
Diagram