As shown above, I have made a speaker that is controlled by the amount of light that it receives. Bonus: I have found the perfect filter on YouTube for my project!
Once again I am using phototransistors as analog inputs, one of them controls the pitch of the sound and the other the duration. This way we get an instrument that can be controlled with both hands of the user. It is interactive and it provides hours of fun, although the square wave form will quickly give the audience a headache.
Have you ever found yourself too lazy to reach for the switch to turn on a lamp? Ever needed an indicator that the sun has already set? Or just wanted to check if your flashlight was on? Introducing a lamp that switches itself on when the light is low in its surroundings.
After thinking hard what could be a switch that doesn’t need hands to switch itself on or off, I have came across the phototransistors in my Arduino Starter Kit and had a “Eureka!” moment with them. They can detect the change in light and don’t require touch to switch on or off.
At least on paper. Due to the characteristic of the phototransistor, the switch only happens in total darkness and during exposure to direct light. But it can easily detect your flashlight if you are pointing at the sensor from point blank.