Re: home and limit switch in series

["Joel Jacobs" <jj-at-netexp.net>]

Seems kinda complicated to have so many switches for home/limit.  Wouldn't
this work?

Just two NC switches in series or two NO switches in parallel for each
axis - only three pport inputs used - one for each axis.  The same switches
could be used for home and limit.  Each axis moves at HOMEING_VEL in the
direction of HOMING_POLARITY until it hits a switch.   The axis then would
decelerate to a stop and slowly back up until it's off the switch.  It could
optionaly continue until an index pulse is recieved from an encoder or a
hall switch on the lead screw.  This position would become 'machine zero'.
Then move to HOME_OFFSET at HOMING_VELOCITY and reset axis position to HOME.

Using this method EMC would have to know which way it was moving when it hit
a limit.  If it hits a limit maybe it should stop and back off the limit
before entering Estop.  That would reduce the possibility of the machine
being turned off with a limit switch activated.

Well, thats my .02

Joel