Just put your mug on the coaster, and the weight of it activates a hidden switch ... starting at the sensor.” [MakeFunStuff] paired this easy-to-use sensor with an Arduino Nano and five LEDs ...

Here is a simple general-purpose security alarm circuit built on the Arduino ... switch in the arduino board. In this way the owner is informed that the alert went off atleast once during his/her ...

He built this set of no-contact limit switches using a hall effect sensor. The small black package sticking out past the end of the protoboard is the sensor. It is used to detect a magnetic field.