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Ultrasonic proximity switch using IC555 and comparator.

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 1.Circuit diagram: Components: 1. IC555 - 2pcs 2. LM358 - 1pcs 3. HC-SR04 (ultrasonic module) - 1pcs 4. Transistor BC547 (NPN) - 1pcs 5. 10K pot  6. LED and buzzer 7. Capacitors - 10uf, 0.1uf, 100uf 8. Resistors - 18K, 4.7K - 2pcs, 47K, 3.3K, 82K, 1K - 2pcs, 220 ohm - 2pcs Circuit working: * Trigger pin of HC-SR04 is given a 526HZ square wave signal generated by IC555 in astable mode. * Trigger pin requires a high to low pulse to trigger the ultrasound transmitter, then it sends short bursts of 40KHz ultrasound. * The sound bounces of the object in-front of the sensor and is received by the receiver this causes the echo pin to go high, the amount of time it's high is proportional to the distance between sensor and object.     * Demo video of the circuit's working is available on my YouTube channel.   Click here. About myself: I am a independent electronics enthusiast who makes interesting circuits for other electronics enthusiast and students who want...
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Ultrasonic proximity indicator (3 transistors)

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 This circuit along with ultrasonic sensor module HC-SR04 detects an object in front of it and gives a linear indication of the distance between the object and the sensor using output LED and a speaker. The speaker starts to make a sound when the object is 1m apart from the sensor as the object approaches nearer and nearer to the sensor the sound gets louder. This indicates that the intensity of sound is proportional to the distance between the object and the sensor.  How HC-SR04 ultrasonic module works? The HC-SR04 sensor has one transmitter and one receiver. The transmitter produces ultrasound which has a frequency of 40KHz and therefore it's inaudible to human ears. The receiver is tuned to pick up ultrasound, as most of the objects reflect sound, the sound reflected back by the object in front of the sensor is detected by the receiver circuit. A signal proportional to the time it takes for sound to reach the object and then back to the receiver is generated by the echo pin...
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