re:limit switches: mech vs proximity

Jack,

This has been pretty extensively covered in prior threads on this
list. Try a search of the archives.

Most commercial machines use a combination of mechanical (to see when
we're close); and optical or proximity (often gauging leadscrew
rotation) for final position. The "index pulse" of an encoder is
often used if encoders are present...

Many "homebrew" setups are using mechanical only. Many are using
proximity(or optical) only.

Another point: Most commercial machines will have 5 switches per axis!
2 for hard limit(usually mech.). 2 for soft limit (mech. or prox.).
And 1 for home (which may REALLY be 2 switches AND'ed together as
first described above. Most home systems have 3 or less.

To really answer your question involves more than "mech. vs. prox."

Like so many other things, there are "quality levels" of EACH TYPE os
switch! Comparing types without taking this into consideration is
folly, IMO. Each type has pluses and minuses, and these +/- are
further modified by the quality level of the SPECIFIC switch in
question...

Sorry The answer isn't simpler.

Ballendo

>Is there a strong reason to prefer one type over another, if either
>was compatible w/ the control system?

>Maybe a prox sw could be mounted on a spring mechanism to protect it?

This is an interesting idea. Most prox. switches are mounted so that
the travel "passes by" the switch, making this sort of setup un-
necessary.