While talking with a friend a few days ago I thought about switches and mechanisms and googled for coin mechanisms. This site underthepier has a great guide to how to make coin mechanisms on your own, and it seems like the best methods are as follows:
- inductive sensor (triggered when metal is close)
- opto switch (triggered when light beam is broken)
- torque switch (triggered when a tiny lever arm is depressed by a small weight)
I also recalled that i once had a device with a "wind" detector. It was a electric candle which would "go out in the wind", but it did not actually measure airflow. I took it apart one day and realised it was a microphone inside with an amplifier! When the wind blew, it blew against the tiny mic which was amplified. When another sensor detected the sound waves, this triggered the off switch.
I don't know what are the local brands for coin acceptors. I suppose the toy capsule dispensers ought to have this sorted though! The ones that are popular here are the Gashapon (ガシャポン) machines, called so because of the "gasha" noise they make when you turn the lever and the "pon" when the capsule is ejected. I wonder if there is a cheaper localised version of this tikam tikam machine that one can buy and repurpose....