I went to the mini Maker Faire at the Singapore Science Centre.

In the video, there’s a device that measures distances using ultrasonic waves, and based on that, turns a light on or off. It took me a while before I finally understood the concept. I thought it was directional, because she explained the device by pointing it up and down for light-on and light-off. Then I asked if it could be programmed to understand sideways directions…

Basically, if you block the emitting device (ultrasonic waves) within a certain distance, the light switches on. That’s why pointing to the ceiling switches it off, because the distance between the device and the ceiling exceeds the programmed distance limit.