Recently an ad on YouTube about an acoustic light sensor/switch module piqued my interest. Out of curiosity, I contacted the online vendor and bought a pair. Named MR-SK50A, the module is less popular ...

At one end is an LED and at the other the LDR, and when attached to a glove it provides a finger sensor without the fuss. The amount of light reaching the LDR from the LED decreases as the pipe is ...