RE: [CAD_CAM_EDM_DRO] Limit and Homing switches Over 2200 members today

Hi Alan -

The idea of AND'ing a low-repeatability switch with the encoder
index pulse sounds like a great low-cost method of finding a
precise home. Is it really that simple? You just look for the
AND'ed signal and set that as home? Wouldn't you have to
calibrate the alignment of the index pulse to the homing/limit
switch? Or, can you just have, a short ON-time of the coarse
switch, which would necessarily be less than the axial travel of
one revolution of the encoder? Could you elaborate? I'd like to
leave room for something like this on my interface PCB, if it's
simple enough.

TIA,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Alan Marconett KM6VV [mailto:KM6VV@...]
Sent: Wednesday, March 06, 2002 5:38 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Limit and Homing switches Over 2200
members today

Hi Bill,

Small lever switches like Microswitch are available surplus, they
are
fine for limits. They may not be repeatable enough for limit
switches.
Optical switches (optical interrupter) are fairly small also, look
like
a 'U' with feet. A thin blade passes through the 'U', and
actuates the
switch. Normally they are TTL output, which is easy to use, but
you
can't "daisy chain" them. Optical switches can be found on HP
laser
printers ;>) and floppy disk drives. They can be quite
accurate for
home position, if their output is AND'ed with a phase of an
encoder or
stepper motor phase. TTL logic should be fine for this.

Congrats on the 2200++ members!

Alan KM6VV
Need Pix?

wanliker@... wrote:

>
> I am converting an EMCO COMPACT 5PC lathe to more modern drives,

G-320, with

> servos, instead of the old steppers.
> I have now come to the part where i have to think about Limit,

and Home

> switches.
> Has anyone on the list got the answers to what I should use.

This is a 5 x

> 12 lathe so something bit would be very hard to mount and use.
>
> So any suggestions, and part numbers would be welcome, with the

emphasis on

> small, being a high priority.
>
> I have noticed on several surplus, (not lathes,) that they are

using optical

> switches, any comment on repeatability and how to tie them into

the system?

>
> Help,
> bill