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Hardware Setup

This guide explains the hardware required for the ESP32 Distance Sensor Workshop and how to wire up the components.

Setup

Required hardware

ESP32 WROOM-32F development board

Note: The board shown in the picture is an ESP32 Relay X2, but any ESP32 development board can be used for this workshop.

The ESP32 Relay X2 board features two onboard relays and supports a wide input voltage range from 5V to 60V, making it suitable for 12V, 24V, or 48V systems such as solar power batteries. However, it does not include a built-in USB serial connector, so you will need an external USB-to-serial adapter for programming and debugging. If you use a different ESP32 development board with onboard USB, the external adapter is not required.

ESP32

USB serial adapter

Here we see a CH340 USB-A to TTL-Serial adapter. Many ESP32 development boards already include a built-in USB-to-serial adapter, so this external adapter is not required if your board has onboard USB connectivity. Use the external adapter only if your ESP32 board lacks a native USB port for programming.

USB Serial Adapter

HC-SR04 ultrasonic distance sensor

The HC-SR04 ultrasonic distance sensor works by emitting an ultrasonic pulse from its trigger pin and then waiting for the echo signal to return. The sensor itself does not calculate distance; it simply provides a short trigger pulse input and then outputs a pulse on the echo pin whose duration corresponds to the time taken for the sound to travel to an object and back. The ESP32 microcontroller measures this echo pulse duration using a hardware timer and then calculates the distance based on the speed of sound. This approach enables accurate, non-contact distance measurement for robotics, automation, and IoT applications.

HC-SR04

The WS2812 is an addressable RGB LED strip, often called "NeoPixels," where each LED can be individually controlled for color and brightness using a single data line. For this workshop, a strip with 40 LEDs is recommended, providing a clear and colorful visual display of measured distances.

LED Strip

Wiring overview

  • Connect the HC-SR04 trigger pin to the GPIO13 PIN and the echo pin to GPIO12 pin on the ESP32.
  • Connect the HC-SR04 power to the 5V pin and ground to any GND pin of the ESP32 board. For details, see requirements.
  • Connect the WS2812 data line to the ESP32 GPIO12 pin (see also requirements).
  • Connect the WS2812 ground to a GND pin.
  • Connect the WS2812 5V Vcc to a 5V supply; if your board lacks a 5V pin, use an appropriate external 5V supply and common ground.
  • Connect the ESP32 module to GND and 5V of the USB Serial Adapter and cross-connect the TX/RX lines.
    +-------------------+         +-------------------------+
    |   USB Serial      |         |      ESP32 Board        |
    |   Adapter (CH340) |         |    (ESP32 WROOM-32F)    |
    +-------------------+         +-------------------------+
    |                   |         |                         |
    |   5V   -----------+---------+--- 5V                   |
    |   GND  -----------+---------+--- GND                  |
    |                   |         |                         |
    |   RX   -----------+--\   /--+--- RX (GPIO3/U0RXD)     |
    |                   |   \ /   |                         |
    |                   |   / \   |                         |
    |   TX   -----------+--/   \--+--- TX (GPIO1/U0TXD)     |
    |                   |         |                         |
    +-------------------+         +-------------------------+

Note: TX on the adapter connects to RX on the ESP32, and RX on the adapter connects to TX on the ESP32 (crossed lines).

Pro Tip: Double-check your wiring before plugging the USB Serial Adapter into your PC or laptop — better safe than sorry.