Limit switch to control motor...

[Norman Pirollo]

Need some advice..

I am designing a small feed system for lumber grading.
This feed system is part of a lumber grading system.

There is a motor drive feeding the individual boards along a
horizontal surface using rubber wheels or rollers.
The feed motor is started manually with a magnetic switch.

At a certain point the piece of lumber should activate a limit or
proximity switch indicating the lumber is correclty against the
horizontal surface of the grading component ( very important to
correctly grade)

If the board rises above the surface , even as little as 1/3 in., the
limit or proximity switch should shut the feed motor down using the
same magnetic switch used to start it..(severly warped board, etc..)

I wish to use one limit/proximity switch to do this.
The difficult part is that the switch is normally open while the board
is being fed through, then becomes closed, then open if there is a
problem.

The open switch then needs to shut the feed motor down...

I have been looking at metal roller ball type switches, preferably
dust-proof and rugged.

How to perform this trickery?


Norman