Steve/Dave
Many thanks for the comments/suggestions.
To be honest, the delay after finish should really be a software thing on the DSP. However, my exhaust system is actually an inline fan extractor system - sans timer. I can just get the timer for the unit and set it to 20s or so - then it will hang on for 20s after switch off (like in the bathroom
). By the time I wire up a 555 and relay or similar to do the job, it would cost more than getting it on ebay sadly - such is the way of things.
On the refrigeration front, I have a nice radiator that was plucked from a YAG laser system - unfortunately, the pump and PID controller were broken.
I have a hole cut to fit a 120mm fan in the rear of my cabinet and I'm sure that it would be fine with that. Some extended tests done by a friend with his laser system suggest that keeping control of the water temp keeps the laser cutting/engraving levels much more consistent and I think I'll go down that route. He uses an external Chinese style cooler (refrigerated rather than air cooled) - that is probably the best bet, but not in the spirit of opensource LOL
Cheers
Neil