PC triggered circuit

Hi all.

What methods are there for getting software on a pc to trigger a circuit?

The software is Autohotkey so there's quite a bit of versatility in that area.

As it would be going on a work computer it would be best if it didn't involve opening the case and chopping wires!

I was thinking of having some kind of sensor looking at an area of the screen for a change in brightness or something to that effect. Is there a sensor that will do this?

not sure if this would help but why not connect to the parralell port? there is a program called something like relaise timer that you can use to turn things on and off at set times or manually thru the printer port..not sure if this is what you wanted

oh btw i only really know alot about chickens!! so i maybe not the best person to ask

Do you have a parallel port?
Do you have a serial Port?
Can you program in VBasic?