I use this battery operated irrigation unit from about May to November to water garden plant pots and hanging baskets:
I'm thinking of improvising a circuit to let me use it as a timer for other indoor purposes during the rest of the year. Such as burglar deterrent lamp switching, etc, capitalising on its neat setting controls.
I'm reluctant to hack into its well-hidden circuitry, and also risk its weatherproofing. So I'd need to front it with a microphone and filter to detect the sound it makes when it switches on or off:
What would be a good starting point for a band pass filter for that4-second noise please?
As a side question, anyone know whether there's a web-based tool onto which I could drop that WAV file and get suggested passive or active filter circuits?
Terry, East Grinstead, UK