Re: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay

Hello Scott,

Another solution is to slow down the switching time. The high voltage
spike across the open switch is generated because the switch opens in a
few microseconds. If the switch opened slowly, over a half second or so,
the spike would not be as great.

I only mention this for academic reasons. You really cannot control the
switching time unless you design the switching circuit with this time
delay in mind. The logic switches in the parallel port will be fast and
there is not anything you can do about that.

You would have to design a slow switching external circuit that responds
to the parallel port switching. Way more trouble than it is worth for
simple relay on/off control.

Tom Hubin
thubin@...