In a previous lectures, we've outlined Scratch bot car, all of which can plug directly into the Raspberry Pi's GPIO ports. Here, Adding the HC-SR04 Ultrasonic Distance Measuring Sensor Module into the Scratch bot car. The HC-SR04 ultrasonic range finder is very simple to use, however, the signal it outputs needs to be converted from 5V to 3.3V so as not to damage our Raspberry Pi! I will introduce some Physics along with Electronics in this tutorial to explain each step!