Ultrasonic
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Ultrasonic Sensor
An ultrasonic sensor is an excellent way to detect obstacles.
Example: HC-SR04
Distance 2 to 450 cm
Current 15 mA
Wiring
Ultrasonic Module VCC (+5V) — PCB VCC (+5V) Ultrasonic Module GND — PCB GND Ultrasonic Module Trigger — PCB Digital Pin Ultrasonic Module Echo — PCB Digital Pin
An internal schematics of the sensor can be found here.[1]