Try playing with door sensors. They are simply two magnets that are open or close. The detection effect is very visual. The sensor opens or closes and you get a signal.
Door sensors have come a long way and are wifi-enabled these days [1]. Link them to your phone (or iPad if doing a projection on TV). Tape the sensors to door, window, drawer, your jacket, etc. Open them and see the signal sent to your phone.
Door sensors have come a long way and are wifi-enabled these days [1]. Link them to your phone (or iPad if doing a projection on TV). Tape the sensors to door, window, drawer, your jacket, etc. Open them and see the signal sent to your phone.
[1] https://www.amazon.com/s?k=door+sensor+wifi