HC-SR04 Ultrasonic Distance Sensor

Ultrasonic ranging module. Measures distance 2cm to 400cm using echo time. GPIO trigger and echo pins.

Sensor HC-SR04 acoustic gpio Draft

This entry is draft and has not been confirmed against physical hardware. A conforming tool will refuse to provision it. The datasheet is the authority, not this page.

Specifications

Protocol gpio
Sensor type acoustic
Model number HC-SR04
Read interval seconds 10

Readings

SlugDevice classUnitRange
distance distance cm 2 to 400

Wiring

PinRequiredNotes
trig Yes
echo Yes Outputs 5V. Must be divided or level shifted to 3.3V before reaching a GPIO input.

Supply: 5V

Failure modes

  • The echo pin idles at 5V. Connecting it directly to a Raspberry Pi GPIO will damage the pin. A divider or level shifter is mandatory.
  • Measurement is timing based and is corrupted by scheduler latency. Occasional wild readings are expected and must be filtered rather than published.
  • Returns no echo for soft, angled or very close targets. A timeout is a valid outcome, not a fault.
  • Speed of sound varies with air temperature. Uncompensated readings drift by roughly 0.2 percent per degree.

Entry

Keyhc-sr04
StatusDraft
Revision1
Registry0.3.0
Entry on GitHub JSON for agents

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