Circuit diagrams and schematics - Electronic projects

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red [...]

This circuit is a simple visible light or IR detector for testing any equipment which outputs light. The circuit can be also used for measuring ambient light levels. This circuit is based on one photodiode which is used in photocell mode so that the photodiode generates a voltage and current signal when it get light. [...]

Reverse engineered circuit diagram of one more commercially produced solar lamp. This one is very similar to the one above, but it is brighter and contains an extra capacitor. Read more original source: http://members.shaw.ca/novotill/SolarGardenLight/index.htm