Occupancy Time Threshold For Pir-Activated Device

[spacechimp]

HI!!!

I have a security light and an extractor fan each activated by its own PIR sensor. What I would like to be able to do is to set each sensor not to turn on the connected device till the body heat trigger has been continuously present for a minimum time period. Is this possible? Can an idiot do it and can I do it cheaply? Is there a ready-made solution already on the market (I have looked long and hard online without joy)?

(Please note: I am not talking about adjusting how long something stays on once it's been triggered!)

Many thanks,

spacechimp!

[spacechimp]

(I was thinking that the initial positive could trigger a countdown to another check, which, if positive, would prompt "all systems go". But I don't know a thing about electronics so I would rather buy something)

[Hymie]

I think that you have identified a gap in the market – many fans operated when the room light is switched on are available with a delay, but not it seems those controlled by PIRs. It would certainly be easy to design such a circuit – but not so easy to retrofit it.

As an alternative solution, I would try part masking the PIR detector such that a person has to reach a particular location within the room to activate the PIR. This can be easily done with opaque tape cut to shape and stuck on segments of the PIR sensor. Not a very elegant solution, but it may stop unwanted long timed (unnecessary) running of the fan.

[spacechimp]

Thank you Hymie. I did actually try masking the sensor for the loo (so it would only come on if someone was sitting in a particular place...) but I would still like to know how to go about incorporating a delayed start. Is this the sort of thing I need, and how would I wire it in? The sensor for the fan seems to operate at 5V.

[spacechimp]

Oh, it stripped my link: http://dx.com/p/5v-high-low-dual-functional-level-trigger-delay-switch-module-blue-201085