Chapter 4. Sensors and input

 

This chapter covers

  • The role sensors play in projects as transducers, converting physical phenomena to electrical signals
  • How microcontrollers use analog-to-digital conversion (ADC) to interpret incoming analog signals
  • Building voltage divider circuits to read resistive sensors like photoresistors
  • Using Johnny-Five’s generic Sensor class to read sensor data and listen for data and changes
  • Taking advantage of Johnny-Five’s component-specific Thermometer and Button classes
  • Managing default digital logic levels using pull-down resistors

To build nifty gadgets, whether they’re temperature-controlled automatic fans or more interesting inventions, you’ve got to be able to gather information and input from the real, physical world.

For this chapter, you’ll need the following:

  • 1 Arduino Uno and USB cable
  • 1 photoresistor
  • 1 4.7 kV resistor
  • 1 TMP36 analog temperature sensor
  • 1 push button
  • 1 10 kV resistor
  • Black, red, and green jumper wires
  • 1 half-size breadboard

Analog and digital sensors pay attention to a particular phenomenon in the physical environment—temperature, brightness, dampness, pressure, vibration—and they output information about changes in the intensity of that phenomenon as a signal. In the automatic fan example in chapter 1, a temperature sensor translated temperature changes into an electrical signal that the microcontroller’s firmware could read and process (figure 4.1).

4.1. Working with analog sensors

4.2. Digital inputs

Summary