Ultrasonic Sensors

Principle: Measure distance using sound waves (typically 40 kHz). Emit a pulse, measure echo return time.

Common Model: HC-SR04

• VCC 5V
• Trig Trigger Input (5V TTL)
• Echo Echo Output (5V TTL)
• GND Ground

Range: ~2cm to 400cm | Accuracy: ±3mm

Timing: Send 10μs trigger pulse → Wait for 8-cycle 40kHz burst → Measure Echo high-time (time of flight).

Distance (cm): duration / 58

Design Tips:

• Avoid mounting near edges or angles
• Consider temperature compensation for precision apps
• Use decoupling capacitor (100nF) near VCC-GND
• Not ideal for soft/angled surfaces