Inputs

1. Light Dependant Resistors (LDR)

LDR is a component whose resistance changes in response to the amount of light shining on it. The standard component is the ORP 12 with a dark resistance of 1M ohms and a light resistance of 500 ohms. Typical use is on top of a lamppost to turn the street light on and off depending on the light level.

2. Thermistors

Thermistors are small components whose resistance changes in response to heat.

NTC (negative temperature coefficient) type thermistors.
The resistance decreases as the temperature increases and the output voltage increases.

3. Other Inputs.