For this final example, I would like to build a device that displays the current temperature by using a dial and we will use two new components for it:
A thermistor or temperature-dependent resistor as a sensor
A servomotor as an output device to move the dial needle
Dealing with the thermistor is nothing new as it is just another kind of variable resistor and we will connect it to Arduino by once again creating a voltage divider. There is nothing new here.
Servomotors are a special kind of motors that don't freely spin, but are able to position at a specific angle and stay there instead thanks to a feedback mechanism and additional circuitry included in the motor case, and are depicted in the following image:
A thermistor and a small servomotor
The use of servomotors is very common in a multitude of projects but their management may be a bit tricky due to the fact that they need a specially forged train of pulses to operate.