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Author Topic: wiring diagram for limit switches  (Read 19719 times)

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Offline Sweep

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Re: wiring diagram for limit switches
« Reply #10 on: October 28, 2008, 02:53:33 PM »
I thought I would tag my question onto the bottom of this old post as it seemed pretty appropriate.
On page 4-8 of the Mach3 users guide there is a diagram for wiring the limit switches. What I don't understand though is what the 5volt supply does. I have tried taking a +5 volt from a USB and feeding it via a 470ohm resistor but it doesn't work. I then read the mail below and that suggests that the PC has its own +5v supply from the parallel pin port (PPP) and that the PPP has its own built in resistor, though that seems to contradict what is written by Art & John Prentice on page 4-9; "Note that for relaible operation you need to "pull up" the input to the parallel port. As mechanical switches can carry a significant current a value of 470R is shown which gives a current of about 10 milliamps."
I have run a simple loop from a PPP input via my machines proximity switches back to PPP 0volt and that seems to work fine so I guess that what is written on this earlier thread is true, but I can't ignore what is written in the manual.

Clarification would be appreciated

Thanks ...Sweep