Homebrew PCBs

On Friday 22 September 2006 01:18 pm, bigjamma wrote:
> For example, I have a need to route the output of my drives on the
> basis of a three-position switch: e.g. "Off | Mill | Lathe".
> When "Mill" is selected, one group of output terminals become "live",
> when "Lathe" is selected, a different group becomes live.
> I could almost handle this if all outputs were 5V TTL signals.
> Unfortunately, only 7 of the 9 are. The other two drive the motor at
> up to 80VDC @ 20A. This is clearly beyond simple signal switching,
> and I don't have the experience in power circuit design to figure out
> how to proceed.

thats not good
disconnecting the motors while the system is powered up will blow
the drives pretty much instantly

you'd be better off getting the extra drives so you have one for 
each motor ,using separate power switches for mill and lathe
and putting a switch box on the TTL signals only

Brian
-- 
"Nemo me impune lacesset"