Re: "att caudlet" Limit switch problems

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <info@t...> wrote:

> Okay, I studied this drawing again and realize that you have a 10K
> tied to +5 on one end and the other is tied to one of the contacts

on

> the switch and that contact is in turn tied to a parallel port

pin.

> In essence you have an external 10K pull-up. Activation of the
> switch pulls the pin low. By wiring the switches in parallel you
> have created a logic "NOR" gate so that if any switch is activated
> then then pin should go low. By tying the Home pin to the Limit

pin

> you are connecting these port pins together. Assuming they each

have

> internal pullups that could cause problems/interactions on the

pins.

>
> If you want to continue to use this setup put small diodes in
> series with each switch so that the cathode is connected to the
> junction of the pull-up and the pin and the anode goes to the

correct

> parallel port pin. There should be a separate diode for each

switch.

> It's okay to tie two or three of the anodes together at a single

port

> pin. This will isolate each switch so that the condition of the
> other switch or the state of a given parallel port pin will not
> effect another.
>
> Drop me a line if it doesn't make sense and I will draw a

schematic

> (I am no good with ASCII drawing :=o)

Hello Caudlet,

I am lost as to why the X and Y axis had been working perfectly for
several weeks on the original wiring set up and just by connecting Z
axis it has now killed all the axis's.

One thought, what if the resistor was sold to me as 10k but was not
say if lower or higher in value? I do remember I had replaced the Y
and Z axis resistor this time as well.

Regards
Shelby