RE: [CAD_CAM_EDM_DRO] Re: Limit Switches ???

Guys:

I doubt that you really need excellent repeatability for limit switches,
unless those switches are also being used to determine the home positon of
the tool. A limit switch is set to trigger somewhere between a soft limit
(essentially a count of the number of steps travelled from some "home"
position) and between the hard limits of the machine. It's function is to be
benign while the carriage is within a "legal" envelope and to change state
whenever the carriage moves out of that envelope towards the hard limit so
the motor can be stopped before the carriage literally crashes into the hard
stop at the end of the travel.

I'd stay away from automotive points since they might be difficult to mount,
are uninsulated from the chassis, and require a relatively strong force to
open. I'd be more apt to use a microswitch (these are also cheap) in a
normally closed circuit. Thus, if either the carriage opens the switch, or
something causes a wire to break, you're protected.

-- Jerry


|-----Original Message-----
|From: mart_wid [mailto:vwa1244302@...]
|Sent: Thursday, May 30, 2002 2:12 PM
|To: CAD_CAM_EDM_DRO@yahoogroups.com
|Subject: [CAD_CAM_EDM_DRO] Re: Limit Switches ???
|
|
|--- In CAD_CAM_EDM_DRO@y..., "reed_irion" <Reed_Irion@h...> wrote:
|> Any suggestions on who and how much for some limit switches with
|> decent repeatablity? Since my first XY table is mainly
|experimental
|> Im looking for some cheap.
|>
|> Any good website discussions on limit switches ?
|>
|> Thanks in advance for any suggestions.
|>
|> Reed
|
|Well I haven't tried this myself, but I can't see why Contact
|Breakers (Points) from a car ignition system wouldn't work if
|carefully setup. They're cheap, readily available, come in many
|configurations and can be safely overun by 1 or 2 mm. They are also
|designed to activate instantly (for consistant ignition timing) and
|so should have good repeat.
|
|Hope this helps, Martin.
|
|
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