This is an Arduino-based Proximity Sensor circuit wired ... see the burning eye of the red LED when there is no object in the safe-zone (within 5 cm from the HC-SR04 module), and an ear-splitting beep ...

With each contact you make, the red LED lights up, the buzzer beeps and the seven ... with only an Arduino UNO, ultrasonic sensor, force-sensitive resistor (or push button), and piezo buzzer.

To supply targeting data for the launcher, an Arduino Uno uses an ultrasonic sensor pair mounted atop a servo. As the servo rotates, the returns from the ultrasonic sensor are plotted on a screen ...