z axis probe connection

[thewww]

Hello my first post so please be gentle. I wish to fit a z axis probe to my newly acquired ancient Chinese 3020 mill, I am running mach3 and the controller has the yoocnc t62-3ax board. I have got it working by connecting the probe directly to pin 15 of my parallel port plug on the computer and allocating it in the software, it works ok but I suspect I need to isolate it somehow.
any help gratefully appreciated
John

[john swift]

by adding to the diagram from
http://georgestone72.blogspot.com/2013/03/yoocnc-t62-3ax-cnc-controller-for-3020t.html

this may help

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john

[thewww]

thanks John but I cannot see that picture on the link you have posted is there another page?

[john swift]

the original picture taken from
http://georgestone72.blogspot.com/20...for-3020t.html

is this -

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it looks like its the x-ray view looking through the board

its possible the input circuit is going to be like this -

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VDD is the +5V supply for the printerport side of the circuit
the common 0V being the input common

on another picture you can see a DC/DC converter to provide the isolated supply for the input circuit

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John