LED Matrix WebServer - ESP32 Projekt

Overview

The LED Matrix WebServer system is a fully configurable LED display solution for home networks. It is based on the NodeMCU-32S ESP32 with up to 12 cascaded MAX7219 8x8 LED modules. Using a simple REST API, messages can be displayed, animations controlled, and sensor data queried.

🎯 Easy to use

Web-based control

Control your LED matrix via HTTP REST API from anywhere in the network

🌐 WiFi integrated

Fritz!Box Mesh compatible

Automatic WiFi connection and reconnect

📡 OTA updates

Update firmware wirelessly

Update your firmware without a USB connection

🌡️ Sensors

DHT22 integrated

Read temperature and humidity

🔊 Buzzer sounds

Tone sequences

Predefined melodies for alarms and notifications

📦 Extensible

Analog inputs

GPIO 34/35/36 available for external sensors

Hardware Components

Component	Model / Type	Features
Microcontroller	NodeMCU-32S ESP32	32-Bit Dual-Core 240MHz, WiFi + Bluetooth
LED Display	12× MAX7219 8x8 Module	cascaded
Sensor	DHT22 (AM2302)	Temperature ±0.5°C, Humidity ±2%
Buzzer	Passive Buzzer	GPIO 16 PWM controlled via NPN transistor
Power Supply	USB-C oder externe 5V PSU	5V for MAX7219, 3.3V internalal for logic

Pin Configuration

GPIO Pin Assignment

LedMatrix Software V1.08
NodeMCU-32S ESP32 (USB powered)

POWER SUPPLY:
  Micro USB ──→ ESP32 (5V regulator generates 3.3V internal)

SPI SIGNALS (MAX7219):
  VIN 5V  ──→ MAX7219 VCC 
  GND     ──→ MAX7219 GND 
  GPIO 5  ──→ MAX7219 CS  (Chip Select)
  GPIO 18 ──→ MAX7219 CLK (Clock)
  GPIO 23 ──→ MAX7219 DIN (Data In)
  Modul 1 DOUT → Modul 2 DIN → Modul 3 DIN

DHT22 SENSOR:
  GPIO 27 ──→ DHT22 Data
  3V3    ──→ DHT22 VCC
  GND     ──→ DHT22 GND

BUZZER:
  GPIO 16 ──→ Buzzer Control (via transistor)
	GPIO 16 ──1kΩ── NPN Transistor BASE
                    NPN Transistor COLLECTOR ──→ Buzzer +
                    NPN Transistor EMITTER ──→ GND
	Buzzer - ──→ GND (ESP32)

ANALOG INPUTS (optional):
  GPIO 34 ──→ Analog Sensor 1
  GPIO 35 ──→ Analog Sensor 2
  GPIO 36 ──→ Analog Sensor 3

Installation & Setup

Here are photos of various LED Matrix installations in the home network. The systems show different colors and configurations.

Red Installation

LED Matrix with red backlight on iMac

AnyCubic Printer Setup

LED Matrix installation above 3D printer

Green-yellow Installation

LED Matrix with green/yellow LED configuration

Green Close-up

Detailed view of a green LED Matrix with wiring

Blue Installation

LED Matrix with blue brightness
Many pixels defective

Cyan Installation

Multiple modules with cyan-colored lighting
Some pixels defective

Feature Overview

📱

REST API

HTTP-based control of all functions from anywhere in the network

🎬

Animations

MD_Parola Library with various scroll modes

💾

EEPROM Storage

Persistently save and load messages

🔄

Asynchronous Web Engine

Non-blocking AsyncWebServer for reliable performance

🌡️

Sensor Integration

DHT22 read every 60 seconds

🔊

Sounds & Alarms

4 predefined melodies: Error, Done, Warning, Completed

REST API Documentation

All endpoints are accessible via HTTP. The LED Matrix is recognized as ledmatrix.fritz.box in the network.

Base Endpoints

Welcome Page HTML

GET /
Response: HTML Welcome Page with menu

Firmware-Version

GET /version
Response: v1.08 (dht)

Message & Display

Display message (static)

GET /print?text=Hallo%20Welt
Displays a static message on the LED matrix (max 75 characters)

Message with scroll animation

GET /scroll?text=Scrolling%20Text
Text scrolls from left to right across the matrix
Switches back to the last print message afterwards

Test display

GET /test
Displays "Hello world" on the LED matrix

Change LED brightness

GET /set?intensity=8
Value: 0 (dark) to 15 (bright)

Turn off display

GET /off
Turns off the LED matrix (power saving)

Sensor Data

Read temperature

GET /temperature
Response: "23.5" (degrees Celsius)

Read humidity

GET /humidity
Response: "65.2" (percent relative humidity)

Read analog inputs

GET /analog34
GET /analog35
GET /analog36
Response: Value between 0-4095

GET /analogvalues
Response: "1234,2345,3456" (comma-separated values)

Sounds & Buzzer

Success melody (Done)

GET /sound/erledigt
Plays positive tone sequence

Warnings melody

GET /sound/warnung
Spielt Warnings-Tonsequenz ab

Error melody

GET /sound/fehler
Spielt Error-Tonsequenz ab

Completed melody

GET /sound/abgeschlossen
Plays success tone sequence

Example Calls

Control & System

Restart system

GET /restart
ESP32 will be restarted (with display shutdown)

curl Examples

curl: display text

curl "http://ledmatrix.fritz.box/print?text=Hallo%20Welt"

curl: text with scroll

curl "http://ledmatrix.fritz.box/scroll?text=Breaking%20News"

curl: read temperature

curl "http://ledmatrix.fritz.box/temperature"

curl: play sound

curl "http://ledmatrix.fritz.box/sound/erledigt"

curl: set brightness

curl "http://ledmatrix.fritz.box/set?intensity=10"

Technical Specifications

Property	Value	Notes
Firmware Version	v1.08 (DHT)	January 2026
Power Supply	USB-C 5V	~500mA for logic
WiFi Standard	802.11 b/g/n	2.4GHz
LED Display	12× 8x8 Module (96×8 Pixel)
DHT22 Range	-40°C to +80°C	Humidity 0-100% RH
Update Method	OTA (AsyncElegantOTA)	Wireless via HTTP
DHT22 Update Interval	60 seconds	Minimum read interval
Message Buffer	75 characters	Max. length of a message

Code Quality

The code has been thoroughly reviewed and classified as production-ready.

✅ Strengths

Robust WiFi management
Non-blocking Async-WebServer
Errorbehandlung bei DHT
OTA updates implemented

⚠️ Potential for Improvement

Hard-coded SSID/password
Expand input validation

📊 Evaluation

Grade: A-
Production ready
Uptime: 30-45 days normal