Photo interrupters

I have just upgraded from micro switches to photo interupters because of the intermittant limit errors I was getting but I have run into a problem. I can wire up four interrupters and they work as expected but if I try to put in another one nothing works. With four I can see the switches toggle as I make and break the beam but when I fit another one nothing happens.

Interrupters are wired to 5v taken from a usb port via 330 r resistor to the led and then to ground. The transistor side is powered from pport pin 15 on the collector of the first interrupter and the emitter goes to the next interrupters collector, untill the last emitter goes to ground.

Is there any way to get six interrupters so I can have limits on x y and z or will I have to settle for limits on x and y.

Bill

You probably just have too much drop in the 6 series photo-transistors to pull the
parallel port input to a logic low. Without extra parts like gates or comparators
you will probably have to use 2 parallel port inputs.
(say one for the 3 + limits and one for the 3 - limits)

Thanks for that, I was wondering if power was the problem. I never thought about splitting the limits into + and - sides something to have a look at. I did try to set up x and y as all limits and the z as a seperate limit but the step conf wizard doesnt let you do that so I might just have to go your way.

Bill

Back to the drawing board. Looking at the step conf wizard on my netbook there is no option to select max xyz or min xyz which would have been great three optos per line and only two pport lines used, or is there a way to write this into the HAl file. When it comes to coding and things I'm like a monkey with a hammer.

Bill

Yes this is beyond what stepconf can do without help...

You might take a look here:

wiki.linuxcnc.org/cgi-bin/wiki.pl?Homing_And_Limit_Switch

I've looked at that and the hal file and it seems to me that the following should do the trick.

net limit-max <- parport.0.pin.10.in
net min-limit <-parport.0.pin.15.in

net limit-max =>axis.0.neg-lim-sw-in
net limit-min=>axis.0.pos-lim-sw-in
net limit-ma=>axis.1.neg-lim-sw-in
net limit-min=>axis.1.pos-lim-sw-in
net limit-max=>axis.2.neg-lim-sw-in
net limitmin=>axis.2.pos-lim-sw-in

Is it right and is there anywhere else I need to change things.

Bill

Sorted, the hal code worked perfectly. Thanks for the tip on using two inputs PCW I would have been going round in cirlces if you hadnt come up with that one.