Since Cameron Hoerig is an engineering student at the University of Cincinnati, the idea of building a typical beer pong table was out of the question. "I'm an electrical engineering student, so I should have a table that stands out," says Hoerig.
He built an interactive table. On either end of the table - where the cups stand - there are 10 LED rings composed of eight LEDs each. In the middle of each ring there's a photocell. The Ping-Pong ball triggers the sensors and the gadget's software rotates the LEDs, giving the illusion of a light spinning around the cup.
It's impossible to read the documentation but I'm responding to your problem with inconsistent linearity of photocells. Yes, photocells are imprecise and non-linear. Much of the voltage appears across the limiting resistor. Consider putting a transistor as a constant current source in series with photocells, eliminating the resistor. The voltage across the transistor will be a consistent two diode drops. That way, all the voltage change appears across the photocell. I hope I have understood your problem.
Californiaís plan to mandate an electric vehicle market isnít the first such undertaking and certainly wonít be the last. But as the Golden State ratchets up for its next big step toward zero-emission vehicle status in 2018, it might be wise to consider a bit of history.