Mechanical Keyboard x Photodiode Test

 1. Soldering mechanical keyboard and phototransistor for input device

2. Errors: Infinite inputs

3. To solve
    1) Add acrylic box over the keyboard that can only pass light from the upper side
    2) Put sands into the acrylic box enough
    3) with fingers, through the gaps of the sands, can be temporary input for photodiodes.