Optical interupt switch implementation.

[Al_The_Man]

Using the type of optical limit switches described here what kind of repeatability can you get? Thanks. What do big Hass VMCs use for accurately homing?

Most commercial systems do not use the switch itself for homing, the switch is used to indicate when the encoder marker should be searched for.
The servo moves in rapid to the switch, when the switch is tripped, the servo backs off the dog in creep speed and searches for the 1/rev marker pulse.
Al.

[Cartierusm]

I realized that I bought and installed a new outboard DRO right before I realized I was going to convert my bridgeport. So I'll just use that as my reference. It has multiple set points, so I'll set one for home, not that I'll need to use home any more, one for the corner of my vice and so on if I have other jigs with special locations.

It'll take some getting used to, to jog around with Mach3 to get the correct location on the outboard DRO.

But I think I just upped my game a little and stop messing with wiggler edge finders, I just got a Co Axial Indicator so I should be able to find edges with more repeatable accuracy and not have to rely on seeing and feel if the wiggler is aligned perfectly.

[Drools]

In owhite's circuit do the outputs of the H21LOB pin 4 connect directly to a status (10,11,12,13,15) pin on the parallel port?
Do we really need a LIMIT-, and for a limit switch which is NC I should be able to connect a regular "IR emitter/ IR diode" pair in series.
Thanks for the help.

[Cartierusm]

Yes you do need limit switches they are cheap protection, but an optical limit switch, in my opinion, is not necessary. I think the whole point of the optical switch is for homing so people can home and get very accurate repeatability.

[Dropout]

I've been waiting for this thread

I've been wanting to build something similar to reference my tool from the table (I need a fixed 0.125 inch and currently use a piece of plastic).

How repeatable would this be?

Where do I get the components?

How easy would it be to to have a red LED lit when the beam was not interupted and green when it was (or vice versa)?

Thanks!

[Drools]

It seems that I can connect the output (pin4) directly to the PC's parallel port status pins providing the voltage is no more than 5VDC. That is what I figured however I wanted to confirm from someone that had done it. I found a post over on the Mach3 forum that has several users doing this. The Pull-up resistor is built-in on these type of units. What I'm going to test is using the fancier (3pin) units for Homing as they require NO switches and normal (2pin) units for limit switches as they are NC. I only intend on having a LIMIT+ switch but I may install a LIMIT- switch per axis if the installation is fairly simple. One thing I did not find is a complete wiring diagram starting at the PC parallel port and including all the switches for one complete axis.
I have Mach3 running with X/Y axis on LPT1 and Z axis on LPT2 which gives me 10 status pins to work with, 5 on each port. I should have enough pins.

[Drools]

I tried my Opto Inturrpt switches I salvaged from several old printers, part number HOA6335-2 they offer the same functionality as the ones mentioned in the first post of this thread. I wired them as shown here and set Mach3 to use them on pins 10,11,12 one for each pin.
They work great!