Help w/ e-stop circuit design

[owhite]

For the laser cutting table I'm building I'll have several inputs that I'd like to feed into E-stop. For example, the laser is water cooled and I have a switch that stays closed as long as the water runs at 1.5 gpm. The laser has a internal board which reports four different digital states. The states correspond to things like "excessive duty cycle".

So I'd like to tie the output of the water flow switch and the four digital laser outputs to e-stop. I'd guess that would mean I'd have the digital signals drive relays, and then connect all the relays and switches in series to form a normally closed circuit. Anything that breaks that circuit will change the e-stop state on the controller board.

The board I have is described here:

http://www.pico-systems.com/univstep.html

So my question is, can anyone suggest a circuit that would report which switch opened? I guess this would be a bit like a game show circuit that reports who was the first contestant to hit the switch. I have plenty of experience building circuits, but not so much at designing them.

Any direction would be helpful so thanks in advance.

Owen

[HillBilly]

HillBilly

[owhite]

What kind of device is represented by CR_ ?

[HillBilly]

owhite,

CR=control relay, is the common term for a relay in a schematic.

The square is the coil and the switches are labeled to identify which relay the are connected to.

HillBilly

[owhite]

ah, I think I get it. The relays must be dpdt.

True?

If I interpret this correctly then I'd need n-1 poles for n inputs. In my case I'll have at least 5 inputs, possibly more.

Owen