Re: home and limit switch in series

[Doug Fortune <pentam-at-home.com>]

Gene Warren wrote:

>     Here's my .02  ...

>      Never, never depend on the processor to stop the machine in a
> runaway axis condition; it won't do it.

This got me to thinking:  I'm working on my own quad L297/L298
board, and (since I am expecting to wire the Emergency Stops and also
the axis overtravel limit switches in series, all going back to a single
input on the parallel port for EMC to recognize), I can also easily
wire this signal directly to the enable/disable lines on the L297's.

Therefore, you are not depending on the software to halt the machine.

Also I can have an overtravel LED and a momentary enable pushbutton
to re-enable the drivers while EMC tries repositioning the axis (to get
out of overtravel).  Once out of overtravel, the drivers are automatically
re-enabled, so the momentary pushbutton can be released,  and EMC
can try to get out of limit from there with its standard algorithm.

Doug