In this chapter, you will look at recipes for using sensors of various types that will allow the Raspberry Pi to measure temperature, light, and more.
Compared to a board like the Arduino, the Raspberry Pi lacks analog inputs. This means that for many sensors, it is necessary to use additional analog-to-digital (ADC) converter hardware. Fortunately, this is relatively easy to do. It is also possible to use resistive sensors with a capacitor and a couple of resistors.
Most of the recipes will require the use of a solderless breadboard and male-to-female jumper wires (see Recipe 9.8).
Be sure to check out the accompanying video for this recipe at http://razzpisampler.oreilly.com.
You want to connect a variable resistor to a Raspberry Pi and measure its resistance so that you can use the position of the variable resistor’s knob in your Python program.
You can measure resistance on a Raspberry Pi using nothing more than a capacitor, a couple of resistors, and two GPIO pins. In this case, you will be able to estimate the position of the knob on a small variable resistor (trimpot) by measuring its resistance from its slider contact to one end of the pot.
To make this recipe, you will need: