The caution about using 5 volt logic signals with common industrial limit
switches is based on the type of contact material used. Typically these
switches are designed for use with 24 VDC or even 120 VAC and use
contacts made with palladium alloys. This material withstands arcing
well, and also depends on arcing to burn oxidation and contamination
off of the contacts. A 5 volt logic signal does not provide enough
energy to perform this burning/cleaning action and the switch can
develop intermittent high resistance at the contacts if used with
low level signals.
There are mechanical switches designed to work with low level signals
such as 5 volt logic signals. They typically have gold alloy contacts
which do not oxidize. For industrial use they should also be sealed.
Because the gold is applied as a very thin layer, it can be damaged
by high level signals that cause arcing.
PMDX sells a micro-switch with contacts suitable for 5 volt logic or
24 volt logic. They are not suitable for 120 VAC control signals nor
for controlling the coil of a relay. These switches are not fully
ruggidized, but are sealed against liquids, have a roller follower,
and are a bit more durable than typical "micro-switches". See:
http://www.pmdx.com/Limit-Std