State change detection with one switch

[Addohm]

I need to program a ML1400 to detect state changes. It's one input where the input being on, or being off is not a bad thing unless either occurs steadily over a period of time. I can't think of a good efficient way to program this. Could anyone point me in the right direction?

Thanks

 

[nwboson]

How about a positive edge oneshot ORed with a negative edge oneshot feeding an OFF timer? Just in case this is a student exercise I'll forego the ladder logic - but it is just 3 elements on one rung.

 

[beethoven_ii]

I'm not sure I fully understand but if you are saying it should be constantly changing state and if it stops doing so them you have a problem then 2 timers should be able to detect this. One timer is energised with the input on and the other timer with the input off. If either timer ever times out then your problem is detected. If I've misunderstood could you please clarify further.