Unconventional Switch - Heated Coaster

 My idea for a switch was to use a metal coaster to detect when a mug was sitting on top of it. This would trigger a light to turn on in this case, but the overall idea was for it to activate a warming plate of some sort in order to heat the mug and its contents. I, unfortunately, could not find a metal coaster and tried to substitute it with a coin, a mason jar lid, and a candle lid, all to no success. The coin was too small, the candle lid was not conductive enough, and the mason jar was both too small and not conductive enough. I resulted in electrical taping the wires to the candle jar lid and also a piece of aluminum foil to the bottom of the mug. This obviously was not ideal, so I apologize. Alternative outcomes for the device could be to play a sound or dispense a reward when the coaster was used, congratulating the person for using a coaster, which is surprisingly rare for some people to use.