RE: [CAD_CAM_EDM_DRO] Re: Home switches.

Dave,

Here's a home-with-index.pdf
<http://f1.grp.yahoofs.com/v1/YHvSQleKU6dQvI70KdmpS3A08ZLZq1reuP8hZDB8kC1wiK
ShBTzJIkNk7YrHdPhovRuE5pQmUAXUODoiSA_iOolYkYWTag/CIRCUITS/Miscellaneous%20Ci
rcuits/home-with-index.pdf> circuit, found in the files section of this
group. It combines the home and index outputs into a single signal. This
would seemingly be very handy for what you're doing.



http://f1.grp.yahoofs.com/v1/YHvSQleKU6dQvI70KdmpS3A08ZLZq1reuP8hZDB8kC1wiKS
hBTzJIkNk7YrHdPhovRuE5pQmUAXUODoiSA_iOolYkYWTag/CIRCUITS/Miscellaneous%20Cir
cuits/home-with-index.pdf



Andrey







-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of cnc002@...
Sent: Monday, July 11, 2005 8:45 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Home switches.



In a message dated 7/9/2005 10:22:09 AM Eastern Daylight Time,

dave_mucha@... writes:

Are you asking to use the existing end or home switch in combination

with an encoder ?



As I understand, some encoders have a 3rd channel. a single point per

revolution.



It would appear that one could run the axis to the end switch and then

until that encoder point changed state.



That would represent the motor being in one exact location, and not

necessarly the screw or table. But, it does eleminate a chip or dirt

from influencing the home point.



Dave

You are correct, many encoders have a "Zero Channel" or "Zero Pulse" on in

them. Most of the ones I have used or worked with actually have two of
them,

180 degrees apart on the round scale. You first make contact with a limit

switch (or you can use a proximity sensor) then the control begins to look
for that

Zero Pulse, when it sees it, then the control knows it has reached the home

position. Pretty much all of your OEM machines use this type of system, it
is

more accurate because, as you pointed out, it prevents metal or wood chips,

etc. from changing the actual position. However, the controller being used
must

be designed to use that Zero Channel as the pusle is on a completely

different output.



I hope this helps some.



Randy A.





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