This is an Arduino-based Proximity Sensor circuit wired using the popular HC-SR04 Ultrasonic ranging module,used here for non-contact object detection purpose. The HC-SR04 module includes ultrasonic ...

You can choose between the one or two pin approach with the HY-SRF05 Ultrasonic sensors which cost roughly the same as the HC-SR04, so it seems a little odd to hack the SR04 instead of picking up ...

With a standard old HC-SR04 ultrasonic sensor, an audio module and a servo to drive a custom gauge needle he’s made a device which can warn people around you if they’re too close for comfort.