Arduino Nano ESP32 - Web Apps Web Analog Gauge
Overview
This tutorial covers the DIYablesWebAnalogGaugePage class from the DIYables ESP32 WebApps Library. The page renders a circular gauge in the browser and receives value updates from the Arduino Nano ESP32 over WebSocket. The gauge range, units, and decimal precision are defined in the constructor — the browser reads this configuration automatically.
Watch this step-by-step video tutorial demonstrating how to use a potentiometer with the Web Analog Gauge app:
What This Tutorial Covers
- Configuring a gauge page with a custom range and unit label
- Sending sensor readings to the browser on demand using a callback
- Streaming continuous gauge updates from the main loop
- Integrating a potentiometer as the analog input source
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Steps
Follow these instructions step by step:
- If this is your first time using the Arduino Nano ESP32, refer to the tutorial on setting up the Arduino Nano ESP32 development environment.
- Connect the Arduino Nano ESP32 board to your computer using a USB cable.
- Launch the Arduino IDE on your computer.
- Select the appropriate board (e.g. Arduino Nano ESP32) and COM port.
- Navigate to the Libraries icon on the left bar of the Arduino IDE.
- Search "DIYables ESP32 WebApps", then find the DIYables ESP32 WebApps Library by DIYables
- Click Install button to install the library.
- Search for DIYables ESP32 WebApps created by DIYables and click the Install button.
1
void setup() {
- You will be asked for installing some other library dependencies
- Click Install All button to install all library dependencies.
- On Arduino IDE, Go to File Examples DIYables ESP32 WebApps WebAnalogGauge example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables WebApp Library - Web Analog Gauge Example
*
* This Serial.println("\nWebAnalogGauge is ready!");
Serial.print("IP Address: ");
Serial.println(webAppsServer.getLocalIP());
Serial.println("Open your web browser and navigate to:");
Serial.print("1. http://");
Serial.print(webAppsServer.getLocalIP());
Serial.println("/ (Home page)");
Serial.print("2. http://");
Serial.print(webAppsServer.getLocalIP());
Serial.println("/webanalogGauge (Analog Gauge)");
Serial.println("\nSimulating sensor data...");monstrates the Web Analog Gauge application:
* - Real-time analog gauge visualization
* - Simulated sensor data with smooth animation
* - WebSocket communication for live updates
* - Beautiful analog gauge with tick marks and smooth pointer movement
*
* Features:
* - Automatic gauge value simulation
* - Smooth animation between values
* - Range: 0° to 280° (customizable)
* - Real-time WebSocket updates
* - Professional analog gauge appearance
*
* Hardware: ESP32 Boards
*
* Setup:
* 1. Update WiFi credentials below
* 2. Upload the sketch to your Arduino
* 3. Open Serial Monitor to see the IP address
* 4. Navigate to http://[esp32-ip]/web-gauge in your web browser
*/
#include <DIYables_ESP32_Platform.h>
#include <DIYablesWebApps.h>
// WiFi credentials - UPDATE THESE WITH YOUR NETWORK
const char WIFI_SSID[] = "YOUR_WIFI_SSID";
const char WIFI_PASSWORD[] = "YOUR_WIFI_PASSWORD";
// Create WebApp server and page instances
ESP32ServerFactory serverFactory;
DIYablesWebAppServer webAppsServer(serverFactory, 80, 81);
DIYablesHomePage homePage;
// Gauge configuration constants
const float GAUGE_MIN_VALUE = 0.0;
const float GAUGE_MAX_VALUE = 100.0;
const String GAUGE_UNIT = "%";
DIYablesWebAnalogGaugePage webAnalogGaugePage(GAUGE_MIN_VALUE, GAUGE_MAX_VALUE, GAUGE_UNIT); // Range: 0-100%
// Other examples:
// DIYablesWebAnalogGaugePage webAnalogGaugePage(-50.0, 150.0, "°C"); // Temperature: -50°C to 150°C
// DIYablesWebAnalogGaugePage webAnalogGaugePage(0.0, 1023.0, ""); // Analog sensor: 0-1023 (no unit)
// DIYablesWebAnalogGaugePage webAnalogGaugePage(0.0, 5.0, "V"); // Voltage: 0-5V
// Simulation variables
unsigned long lastUpdateTime = 0;
const unsigned long UPDATE_INTERVAL = 500; // Update every 500ms (0.5 second)
const float STEP_SIZE = 1.0; // Step size for simulation
float currentGaugeValue = GAUGE_MIN_VALUE; // Start at minimum value
float step = STEP_SIZE; // Positive step means increasing, negative means decreasing
void setup() {
Serial.begin(9600);
delay(1000);
Serial.println("DIYables ESP32 WebApp - Web Analog Gauge Example");
// Add web applications to the server
webAppsServer.addApp(&homePage);
webAppsServer.addApp(&webAnalogGaugePage);
// Optional: Add 404 page for better user experience
webAppsServer.setNotFoundPage(DIYablesNotFoundPage());
// Start the WebApp server
if (!webAppsServer.begin(WIFI_SSID, WIFI_PASSWORD)) {
while (1) {
Serial.println("Failed to start WebApp server!");
delay(1000);
}
}
setupCallbacks();
}
void setupCallbacks() {
// Handle gauge value requests (when web page loads/reconnects)
webAnalogGaugePage.onGaugeValueRequest([]() {
webAnalogGaugePage.sendToWebAnalogGauge(currentGaugeValue);
Serial.println("Web client requested gauge value - Sent: " + String(currentGaugeValue, 1) + GAUGE_UNIT);
});
}
void loop() {
// Handle WebApp server communications
webAppsServer.loop();
// Update gauge with simulated sensor data
if (millis() - lastUpdateTime >= UPDATE_INTERVAL) {
lastUpdateTime = millis();
Serial.println("Updating gauge value..."); // Debug message
// Simple linear simulation: step changes direction at boundaries
currentGaugeValue += step;
// Change direction when reaching boundaries
if (currentGaugeValue >= GAUGE_MAX_VALUE || currentGaugeValue <= GAUGE_MIN_VALUE) {
step *= -1; // Reverse direction
}
// Ensure value stays within bounds (safety check)
if (currentGaugeValue < GAUGE_MIN_VALUE) currentGaugeValue = GAUGE_MIN_VALUE;
if (currentGaugeValue > GAUGE_MAX_VALUE) currentGaugeValue = GAUGE_MAX_VALUE;
// Send the new value to all connected web clients
webAnalogGaugePage.sendToWebAnalogGauge(currentGaugeValue);
// Print to serial for debugging
Serial.println("Gauge: " + String(currentGaugeValue, 1) + GAUGE_UNIT + " (" + (step > 0 ? "↑" : "↓") + ")");
}
delay(10);
}
- Update the WiFi credentials in the sketch:
const char WIFI_SSID[] = "YOUR_WIFI_NETWORK";
const char WIFI_PASSWORD[] = "YOUR_WIFI_PASSWORD";
- Click Upload button on Arduino IDE to upload code to Arduino Nano ESP32
- Open the Serial Monitor
- The Serial Monitor output should resemble the following:
8
Serial.println("Hello World!");
Message (Enter to send message to 'Arduino Nano ESP32' on 'COM15')
New Line
9600 baud
DIYables WebApp - Web Analog Gauge Example
INFO: Added app /
INFO: Added app /web-gauge
DIYables WebApp Library
Platform: Arduino Nano ESP32
Network connected!
IP address: 192.168.0.2
HTTP server started on port 80
Configuring WebSocket server callbacks...
WebSocket server started on port 81
WebSocket URL: ws://192.168.0.2:81
WebSocket server started on port 81
==========================================
DIYables WebApp Ready!
==========================================
Web Interface: http://192.168.0.2
WebSocket: ws://192.168.0.2:81
Available Applications:
Home Page: http://192.168.0.2/
Web Analog Gauge: http://192.168.0.2/web-gauge
==========================================
- If nothing appears, press the reset button on the board.
- Enter the IP address shown in the Serial Monitor into a browser on a device on the same network.
- Example: http://192.168.0.2
- The home page displays a card for the gauge application:
- Select the Web Analog Gauge card to open the gauge page:
- The gauge is also accessible directly at http://192.168.0.2/web-gauge.
Gauge Configuration
The range and units are set in the constructor and sent to the browser once on connection:
// Parameters: minimum, maximum, unit string
DIYablesWebAnalogGaugePage gaugePage(0.0, 100.0, "V");
The value request callback is called each time a browser connects and requests the current reading:
gaugePage.onGaugeValueRequest(onGaugeValueRequested);
void onGaugeValueRequested() {
int raw = analogRead(A0);
float voltage = (raw / 1023.0) * 5.0;
gaugePage.sendGaugeValue(voltage);
}
For continuous streaming (rather than on-demand), call sendGaugeValue() from the main loop at the desired interval.
Example: Potentiometer-Based Gauge
The library includes a ready-to-use potentiometer example:
#include <DIYables_ESP32_Platform.h>
#include <DIYablesWebApps.h>
// WiFi credentials - UPDATE THESE WITH YOUR NETWORK
const char WIFI_SSID[] = "YOUR_WIFI_SSID";
const char WIFI_PASSWORD[] = "YOUR_WIFI_PASSWORD";
// Define pin
#define PIN_ANALOG 36
// Create WebApp server and page instances
ESP32ServerFactory serverFactory;
DIYablesWebAppServer webAppsServer(serverFactory, 80, 81);
DIYablesHomePage homePage;
// Gauge configuration constants
const float GAUGE_MIN_VALUE = 0.0;
const float GAUGE_MAX_VALUE = 100.0;
const String GAUGE_UNIT = "%";
DIYablesWebAnalogGaugePage webAnalogGaugePage(GAUGE_MIN_VALUE, GAUGE_MAX_VALUE, GAUGE_UNIT); // Range: 0-100%
// variables
unsigned long lastUpdateTime = 0;
const unsigned long UPDATE_INTERVAL = 500; // Update every 500ms (0.5 second)
const float STEP_SIZE = 1.0; // Step size for simulation
float currentGaugeValue = GAUGE_MIN_VALUE; // Start at minimum value
float step = STEP_SIZE; // Positive step means increasing, negative means decreasing
void setup() {
Serial.begin(9600);
delay(1000);
Serial.println("DIYables ESP32 WebApp - Web Analog Gauge Example");
// Add web applications to the server
webAppsServer.addApp(&homePage);
webAppsServer.addApp(&webAnalogGaugePage);
// Optional: Add 404 page for better user experience
webAppsServer.setNotFoundPage(DIYablesNotFoundPage());
// Start the WebApp server
if (!webAppsServer.begin(WIFI_SSID, WIFI_PASSWORD)) {
while (1) {
Serial.println("Failed to start WebApp server!");
delay(1000);
}
}
setupCallbacks();
}
void setupCallbacks() {
// Handle gauge value requests (when web page loads/reconnects)
webAnalogGaugePage.onGaugeValueRequest([]() {
webAnalogGaugePage.sendToWebAnalogGauge(currentGaugeValue);
Serial.println("Web client requested gauge value - Sent: " + String(currentGaugeValue, 1) + GAUGE_UNIT);
});
}
void loop() {
// Handle WebApp server communications
webAppsServer.loop();
// Update gauge with simulated sensor data
if (millis() - lastUpdateTime >= UPDATE_INTERVAL) {
lastUpdateTime = millis();
Serial.println("Updating gauge value..."); // Debug message
// Simple linear simulation: step changes direction at boundaries
//currentGaugeValue += step;
currentGaugeValue = analogRead(PIN_ANALOG);
currentGaugeValue = map(currentGaugeValue,0,4095,0,100);
// Change direction when reaching boundaries
if (currentGaugeValue >= GAUGE_MAX_VALUE || currentGaugeValue <= GAUGE_MIN_VALUE) {
step *= -1; // Reverse direction
}
// Ensure value stays within bounds (safety check)
if (currentGaugeValue < GAUGE_MIN_VALUE) currentGaugeValue = GAUGE_MIN_VALUE;
if (currentGaugeValue > GAUGE_MAX_VALUE) currentGaugeValue = GAUGE_MAX_VALUE;
// Send the new value to all connected web clients
webAnalogGaugePage.sendToWebAnalogGauge(currentGaugeValue);
// Print to serial for debugging
Serial.println("Gauge: " + String(currentGaugeValue, 1) + GAUGE_UNIT + " (" + (step > 0 ? "↑" : "↓") + ")");
}
delay(10);
}
Common Sensor Types
The gauge is suitable for any measurement that produces a floating-point value in a known range:
- Voltage monitoring (battery, power supply)
- Temperature or humidity from a calibrated sensor
- Pressure readings from a pressure transducer
- Light intensity from an LDR
- Any analog reading scaled to engineering units
Troubleshooting
Gauge needle does not move
- Confirm webAppsServer.loop() runs on every iteration of loop()
- Check the Serial Monitor for WebSocket connection events
- Verify the callback is assigned before webAppsServer.begin()
Gauge displays incorrect values
- Check the analog reference voltage for your board
- Verify the scaling formula maps raw ADC values to the configured range
- Add Serial.println(value) in the callback to inspect values before sending
Cannot access the page
- Confirm the IP address from the Serial Monitor
- Ensure the browser device is on the same 2.4 GHz network as the board
- Check that port 80 is not blocked by a firewall