Wow, great input! All of it! Sorry for being so secret about my end goal here - it's for a proof of concept for an invention of a new product, so I'm just protecting the ip :-)
Anyway, your suggestions are really powerful - thanks a lot. I have input for my project :-)
That's a possibility. My thought was, though, to avoid being dependant on having actual line of sight with the bulb. And further, the gadget must only work when the light is on, so no need to store any juice :-)
Hehe - funny guys! :-)
I was thinking of powering my "gadget" through induction from the (weak) EM field surrounding an electric bulb. Hence the need for ultra low power consumption. I'm afraid a sand clock will be a bit too clumpsy, however, I'm really, really into keeping it simple :-)
Which electronic component (or other means) would you use to measure duration, like a timer, if energy must be saves to the maximum?
This component should use as little power as possible, while being able to measure duration up till 5 years with a resolution of, say 100 hours.
In the old...