Added felt pads (leftovers from some IKEA furniture) to the back of the Luke Skywalker Tauntaun Sign
The water flow sensor is normally open (I think), or off. The flow switch is used to protect the K40 Laser Engraver and Cutter laser tube as it uses water as a cooling agent. The idea is to prevent the operation of the laser engraver if the water isn’t flowing.
When I simulate water flow by blowing into the sensor, the switch closes, or turns on.