HC-SR04.rst

Distance Sensor
===============

You have received HC-SR04 ultrasonic distance sensors. This module, which measures distances using ultrasonic waves, consists of four pins:

.. image:: HC-SR04.png
   :width: 500
   :align: center

- VCC: sensor power supply (5V)
- Trig: trigger pin
- Echo: echo reception pin
- GND: ground

Input and Output Voltages
-------------------------

- Power supply voltage (VCC): 5V
- Output voltage (Echo): 5V

Operation
---------

1. **Triggering**: To initiate a measurement, a 10-microsecond signal must be sent to the Trig pin. This triggers the emission of a burst of 8 ultrasonic pulses at 40 kHz.
2. **Reception**: The sensor then waits to receive the echo of these pulses. When the echo is detected, the Echo pin goes high.
3. **Time Measurement**: The duration for which the Echo pin remains high corresponds to the time taken by the ultrasonic wave to travel to the obstacle and back.

Reminder: The speed of sound in air is approximately 343 m/s.

Connection to the Raspberry Pi
------------------------------

.. warning::

   Since the sensor's output voltage is 5V, a voltage divider is required to lower this voltage to a level acceptable for the Raspberry Pi's GPIO pins (3.3V).

Creating the voltage divider:

.. figure:: Circuit.png
   :width: 500
   :align: center

   *vertical resistor: 1K ohm, horizontal resistor: 2K ohm*

- Connect the sensor's VCC pin to a 5V pin on the Raspberry Pi.
- Connect the sensor's GND pin to a GND pin on the Raspberry Pi.
- Connect the sensor's Trig pin to a GPIO pin on the Raspberry Pi (e.g., GPIO 10).
- Connect the sensor's Echo pin to another GPIO pin on the Raspberry Pi (e.g., GPIO 9).