Re: [CAD_CAM_EDM_DRO] A MaxNc Retrofit on my Dyna-Myte 2000 CNC mill

On Tuesday 21 March 2006 11:54 pm, Fred Howe wrote:

> I am retrofitting a dead Dyna-Myte 23000 CNC tabletop mill with a
> MaxNc controller board and software kit that I purchased for about
> $250.00 a few years ago. My problem is the limit/home switch wiring. I
> simply can't make heads or tails out of the single paragraph of
> instructions about how to hook them up. What I have is two loops,
> consisting of the 3 positive limit switches and the 3 negative limit
> switches, set up so that if any switch is tripped, it opens the
> circuit.

Since the paragraph in the description you linked to specifies that the
switches need to be in a grounded state for normal operation, you need one
end of each loop connected to ground and the other end of each loop connected
to the pin for the limit switches, and you also need a pullup resistor
connected between that pin and +5V. A value of perhaps 1K ohms should do you
for that pullup.

> I am hoping to use the same positive limit switches as the Home switches by
> putting a switch in the line and directing the output to either the "Home"
> pin or the "limit" pin, as it appears that it won't work to simply connect
> the switches to both at the same time.

I don't see how this is going to work since operating a switch or having it
not connected to the terminal in question is going to remove the ground and
have it activate the terminal you've disconnected from -- limit, if you move
the switch wires to "home" for example. You could probably get past this
with a bit of external logic, but it would seem easier to me to add another
set of switches.

> What mystifies me is where do I connect the "other" end of the loop?
> Ground?

Yes. See above.

> Someone suggested I had to supply a low level (<50ma) 5 volt source.

Your inputs will probably need a pullup resistor to +5, though it's possible
that some input ports will provide this function for you.

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