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Author Topic: Can all 3 of my homing switches share one pin in Mach 3?  (Read 4752 times)

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Offline bfgstew

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Re: Can all 3 of my homing switches share one pin in Mach 3?
« Reply #10 on: February 04, 2016, 01:30:33 AM »
I think you'll find the BOB powers the opto's on the BOB side, your switches need wiring from pin 15 to ground as stated, it looks for the difference in potential.
« Last Edit: February 04, 2016, 01:42:29 AM by bfgstew »

Offline tombj

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Re: Can all 3 of my homing switches share one pin in Mach 3?
« Reply #11 on: February 04, 2016, 08:53:29 AM »
OK, I'll try it that way.  The LED on the BOB did go on and off when activating the home switch loop though...
thanks
tom

Offline stirling

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Re: Can all 3 of my homing switches share one pin in Mach 3?
« Reply #12 on: February 04, 2016, 11:08:16 AM »
From the schematic you linked to, what you're doing SHOULD work. (Technically, you shouldn't use your BOB's 5V for your switch chain but that shouldn't stop it working it will just trash your galvanic isolation). BUT - if your BOB LED is working then the inputs (at least at the D connector) must be too.

You said the existing limits work - but you said "you think" - do they?

maybe post your xml file.

Offline tombj

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Re: Can all 3 of my homing switches share one pin in Mach 3?
« Reply #13 on: February 04, 2016, 02:53:36 PM »
I just went out to the shop and solved the problem, which was that those optoisolators needed 24v rather than 5v power...I just checked the voltage across the estop input and got 26v, then checked the resistors in place on the BOB, and sure enough they were 2.2k which is what was called out on the BOB schematic for 24v inputs.  Now all is well and homing is working perfectly. I should have looked at the resistors first but what really threw me was the fact that the BOB input LED lit up when operating the switches; now I know that is merely an indication of a signal, not necessarily an ADEQUATE signal!  I'm lucky I already had no hair to tear out..
thanks for all the help!
Tom