hardcore electronics

Analogue Input

Analogue inputs are usefull if you want to know more information about some input. For example, instead of just monitoring if a button has been pushed, you might want to know what force has been applied. In this case a force sensing resistor will not only let you know if the button has been pushed but also with what force. Analogue transducers varies in complexity and working principles, but the most common is the variable resistor. Such a transducer will convert a change in mechanical, light, heat, and other form of energy into a change in resistance.

Analogue inputs are continuously variable signals, in contrast to digital inputs that are either ON or OFF. Analogue inputs are a voltage or current that represent a signal proportionaly. The signal takes any value within a given range to represent a signal, another method to convey an analogue signal is modulation of the input.

Analgue Input circuits are more difficult to design and implement as they are subject to noise and signal interferences.

Analogue Circuits

You can find many analogue circuits online. For inspiration try:
Fritzing, or the basic Arduino tutorials.