Chapter 5: Building a Touchless Handwash Timer
In Chapter 4, Building a Plant Watering System, we learned how the ADC interface works, and we used that knowledge to write libraries for a capacitive soil moisture sensor and a water level sensor. We also wrote a small library to control a buzzer and learned how relays work and used that knowledge to control a pump using our code. Then we used all this knowledge to build an automated plant watering system.
In this chapter, we are going to build a touchless handwash timer. After working through this chapter, you will know how ultrasonic sound sensors work and how to measure distance with them. We are going to utilize this knowledge to create a sensor that recognizes a hand that is between 20 and 30 centimeters away from the sensor to start a timer. The timer will then be displayed on a 7-segment display. While implementing this, we will also learn about the MAX7219 chip and how to use it to control different display types.
In this...
