Technically a photocell sensor captures the light. However when in an indoor space with directly lighting, such sensor can capture human motion since the shadow will change the analog read pretty dramatically. Specifically such change occurs when we approaching the sensor, that the value decays along with the proximity of our hand to sensor. I found such a connect quite interesting, that somehow this motion transits through the ambient light and generates an input value aligned with the motion. It is even more intuitive to see such a relationship between motion, light, and photocell sensor when we generate a graphical output with the analog input by connecting Arduino with P5.js.

So what are the possible occasions that such motion occurs? I tend to categorize them as three types of motion: the first one is to reduce the distance of the object and ourself intentionally, either to reach an object or push a button as a digital input; the second is unconsciously passing by or getting closer to something, say you walking through the hall way and the distance between you and wall gets shorter; the most interesting one to me, is the repetitive human motion we’re conducting, such as running, cycling, and many other types of working out… Since we’re conducting a programmed motion (by our body mechanics, by bicycles, by the music or certain dance moves), there is a rhythm, or even pattern of the proximity of ourselves and object.

On the other side, the output can be various and colorful, that we can link the change of the size associated to the motion (like the video above), or trigger a different program when people get closer. I bought this LED fiber optic to try some ideas by link it with my Arduino, and I programed this interaction between me and the lights. Typically the lights will be constant bright, and we I’m getting closer, the photocell senses the change of the light and the lights start to blink when analog input reach a lower threshold. Also it is interesting to see the difference of the regular LED and such fiber optic lights, which provide a much softer and elegant lighting, with a texture. Materiality and program of the interaction design, this is something I’ll keep exploring.