ESP32 + LoRa: Build a Long-Range Wireless Sensor Node (Up to 8km)

The Problem

WiFi works great — until you need to put a sensor in your garden 200 meters away. Or on a farm across the valley. Or inside a metal warehouse. WiFi dies at 50 meters. Bluetooth at 10.

LoRa changes everything. Using the E32 LoRa module (915MHz, 1W), you can send sensor data up to 8 kilometers — no cell tower, no WiFi, no monthly fees.

What You’ll Build

A battery-powered LoRa sensor node that:

• Reads temperature and humidity
• Transmits data over LoRa to a receiver
• Goes into deep sleep for 10 minutes between readings (battery lasts months)

Difficulty: Beginner  |  Time: 45 minutes  |  Cost: ~$40 in parts

Hardware Required (Bill of Materials)

Frequency Warning: E32 modules come in 433MHz, 868MHz, and 915MHz versions. They CANNOT communicate with each other. Make sure both modules are the SAME frequency. The US uses 915MHz.

Step 1: Wiring (Sender Node)

The E32 LoRa module uses UART serial — much simpler than SPI-based LoRa modules. No complex libraries needed!

TX↔RX crossing: UART is like a phone call — your mouth (TX) connects to their ear (RX). Always cross-connect: module TXD → ESP32 RX2, module RXD → ESP32 TX2.

Step 2: Sender Code

Upload this to the sender ESP32 (the one with the DHT22 sensor):

#include <HardwareSerial.h>
#include "DHT.h"

HardwareSerial LoRaSerial(2); // ESP32 Serial2 (GPIO 16, 17)

#define DHTPIN 13
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// Deep sleep: 10 minutes between readings
#define uS_TO_S_FACTOR 1000000ULL
#define TIME_TO_SLEEP  600

void setup() {
  Serial.begin(115200);
  Serial.println("sensbench LoRa Sensor Node");

  LoRaSerial.begin(9600);
  dht.begin();
  delay(2000);

  float h = dht.readHumidity();
  float t = dht.readTemperature();

  if (isnan(h) || isnan(t)) {
    Serial.println("Sensor read failed!");
  } else {
    String data = "T:" + String(t, 1) + "C H:" + String(h, 1) + "%";
    Serial.println("Sending: " + data);
    LoRaSerial.println(data);
  }

  Serial.println("Deep sleeping for 10 minutes...");
  Serial.flush();

  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);
  esp_deep_sleep_start();
}

void loop() {
  // Not reached after deep sleep
}

Step 3: Receiver Code

Upload this to the receiver ESP32 (connected to your computer):

#include <HardwareSerial.h>

HardwareSerial LoRaSerial(2);

void setup() {
  Serial.begin(115200);
  Serial.println("sensbench LoRa Receiver");
  LoRaSerial.begin(9600);
}

void loop() {
  if (LoRaSerial.available()) {
    String data = LoRaSerial.readString();
    Serial.print("Received: ");
    Serial.println(data);
  }
}

Step 4: Test It

1. Power the sender node with the 18650 battery shield
2. Connect the receiver to your computer and open Serial Monitor (115200 baud)
3. Every 10 minutes, you’ll see temperature and humidity arrive from up to 8km away

Why This Works So Well

• Deep Sleep: The ESP32 draws only 10µA in deep sleep. With a 2000mAh 18650 battery, the sensor node can run for 3+ months on a single charge.
• UART LoRa: Unlike SPI-based LoRa (SX1276), the E32 module uses simple serial communication. No complex library, no SPI wiring mess, no configuration registers.
• 1W Power (30dBm): The E32-915T30D is the high-power version. Standard modules output 20dBm (100mW). This one outputs 30dBm (1000mW) — 10x the power, 3x the range.

Going Further

• Add more sensor nodes: Each node sends data on a different schedule to avoid collisions
• Forward to cloud: Connect the receiver ESP32 to WiFi and forward LoRa data to MQTT
• Solar power: Add a small solar panel to the 18650 battery shield for permanent deployment
• Build a mesh: Multiple receiver nodes can relay data across even longer distances