Skip to content

Breadboards, wiring, and power

Before you connect sensors and actuators to your ESP32, it’s important to understand how a breadboard, wires, and power rails work. This helps you avoid short circuits and “mysterious” bugs.

1. Breadboard layout

Most solderless breadboards have:

  • Horizontal power rails at the top and bottom (often marked with red/blue lines).
  • Vertical columns of 5 holes in the middle; each group of 5 holes is electrically connected.

Key ideas:

  • A component’s two legs must be in different rows to avoid shorting it.
  • You typically create a ground rail (GND) and a 3.3 V rail for your ESP32 projects.
    • The ESP32-S3 is not 5 V tolerant, so do not connect 5 V signals to the ESP32-S3. Connecting 5 V to the ESP32-S3 will damage the board.

2. Connecting the ESP32

When powered via USB, the ESP32 DevKit board can usually provide 3.3 V on a pin labeled 3V3 or similar.

Basic setup:

  • Connect 3V3 on the ESP32 to the red power rail.
  • Connect GND on the ESP32 to the blue/black ground rail.
  • Use these rails to power sensors and simple components (LEDs, small ICs).

Do not power heavy loads from 3.3 V

Motors, servos, and large numbers of LEDs can draw more current than the ESP32’s regulator can safely deliver.
Use a separate power supply for high‑power devices and connect grounds together.

3. Safe LED wiring

The simplest useful circuit is an LED with a current‑limiting resistor.

  • Long leg (anode) → GPIO pin through a resistor (e.g. 220 Ω).
  • Short leg (cathode) → GND.

Example sketch (GPIO 25):

const int LED_PIN = 25;

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(500);
  digitalWrite(LED_PIN, LOW);
  delay(500);
}

4. 3.3 V vs 5 V

Some Arduino boards and many sensors use 5 V, while the ESP32 uses 3.3 V logic.

  • Never connect a 5 V output directly to an ESP32 GPIO pin.
  • Many I²C sensors work at 3.3 V–5 V and can be powered from 3.3 V safely
    • Check the datasheet of the sensor to see if it is 5 V tolerant.
  • For 5 V‑only devices, you may need level shifters or a different microcontroller.

5. Grounding and noise

For stable measurements:

  • Always connect all device grounds together (common ground).
  • Keep sensor wires short where possible.
  • For noisy loads (motors, relays), consider:
    • A separate supply.
    • Adding flyback diodes and decoupling capacitors as recommended by the component datasheet.

Good wiring habits drastically reduce the time you spend debugging hardware issues later.