Arduino Internet Voltage Monitoring

Arduino Internet voltage monitoring can be achieved in several ways. The Arduino can be set up as a client or a server in order to display measured voltage on a web page. In this article an Arduino is set up as web server that hosts a web page stored on SD card. The web page displays the voltage measured on Arduino analog pin A2 in near real-time. The web server also interacts with ThingSpeak, a Internet of Things (IoT) service which logs voltage over time. Voltage is displayed on the hosted web page on a gauge and in a ThingSpeak generated graph or chart.

Arduino Internet Voltage Monitoring

Arduino Internet Voltage Monitoring

How Arduino Internet Voltage Monitoring Works in this Project

The Arduino web server hosts a web page that communicates with the Arduino using JavaScript / Ajax. This allows the voltage to be sent from the Arduino to the web page over the Ethernet connection to update the voltage in the gauge on the web page. A potentiometer is used to vary the voltage on Arduino pin A2 between 0 and 5 volts.

The raw value from the Arduino analog input is sent to the web page and converted to voltage in the JavaScript that runs on the page. The raw analog value is also displayed on the web page and will be between 0 and 1023.

After the voltage is calculated, it is sent to ThingSpeak by JavaScript. ThingSpeak logs the voltage and plots the graph of the voltage. The graph in the above image is created by copying graph code from ThingSpeak which then updates the graph with the data from the ThingSpeak server.

Voltage Update Timing

Voltage is measured by the Arduino and updated on the web page every 200ms. ThingSpeak only updates graph or chart values every 15s (fastest update speed), so the JavaScript code only sends updates to the ThingSpeak server every 20s.

Tutorial for the Project and Other Resources

A full tutorial is available which explains how to set up this project on your own Arduino.

Learn how ThingSpeak works and how to set up a channel to send data from an Arduino to an account on the ThingSpeak server — ThingSpeak is a free service.

Learn about measuring voltage with Arduino.

Arduino Ethernet shield tutorial explains how to set up an Arduino and Ethernet shield as a web server.

 

 

Arduino Uno Interfacing GT-511C3 Fingerprint Scanner Demo Software

ADH Technology, the company that sells the GT-511C3 fingerprint scanner provide SDK software that includes a demo application for running on a PC. The demo software allows the scanner to be used to enrol fingerprints, each with a unique ID and then identify enrolled fingerprints when a finger is placed on the scanner later. The GT-511C3 fingerprint scanner demo software also includes several other functions that allow fingerprints to be deleted, display number of registered fingerprints, etc.

A USB to TTL level device is normally needed to connect the fingerprint scanner to a Windows PC to use the demo application.

Connecting the GT-511C3 Fingerprint Scanner to a PC using an Arduino

The article on interfacing the GT-511C3 to a PC running the demo software provides a quick hack that uses an Arduino Uno as a USB to TTL converter. The Arduino Uno uses a software serial port to connect to the fingerprint scanner because the only hardware serial port on the Uno is connected to the USB chip which is used as the interface to the PC USB port.

Serial data is relayed between the fingerprint scanner and demo software on the PC by a sketch running on the Arduino. The image below shows the demo application and interface to the scanner. Also see the full article that explains the hardware connections and software needed for the project.

GT-511C3 Fingerprint Scanner PC Demo Software using Arduino Uno

GT-511C3 Fingerprint Scanner PC Demo Software using Arduino Uno

How to Use Arduino Serial Ports

Arduino boards such as the Uno, MEGA2560 and Due all have a serial port that connects to the USB device port on the board. This port allows sketches to be loaded to the board using a USB cable. Code in a sketch can use the same USB / serial port to communicate with the PC by using the Arduino IDE Serial Monitor window, or a Processing application for example. The USB port appears as a virtual COM port on the PC.

This article shows how to use Arduino serial ports when additional serial ports are needed for a project.

Arduino Serial Ports Available

The serial port for programming the Arduino mentioned above is a hardware serial port. The microcontroller on the Arduino board has a hardware serial port built-in, so that after the port has been initialized by software, a byte sent to the port will be sent out serially by the hardware.

The Arduino Uno has only one hardware serial port because the microcontroller used on the Uno has only one built-in serial port. The Arduino MEGA 2560 and Arduino Due both have 3 extra hardware serial ports.

Serial Port Technical Details

The hardware serial ports referred to here are UART (Universal Asynchronous Receiver Transmitter) ports. They may be referred to as USART (Universal Synchronous Asynchronous Receiver Transmitter) ports in the microcontroller documentation if they are configurable in both synchronous and asynchronous modes.

Arduino Uno Serial Port

This image shows the only serial port available on the Arduino Uno highlighted in red. The port connects through a USB chip to the USB device port.

Arduino Uno Serial Port

Arduino Uno Serial Port

Arduino MEGA 2560 and Due

Both the MEGA 2560 and Due have 4 serial ports in total. One that connects through a USB port chip to the USB device port on the board and three extra serial ports that connect to pins on one of the pin headers of the board.

Arduino Due Serial Ports

Arduino Due Serial Ports

 

Arduino MEGA 2560 Serial Ports

Arduino MEGA 2560 Serial Ports

Pins 0 and 1 of the Due and MEGA connect serial port 0 through to the USB device port so that these Arduino boards are compatible with the pin numbering of the Uno and therefore with Arduino shields.

The extra serial ports are ports 1 to 3 with each port having a transmit and receive pin.

It is important to be aware that the MEGA 2560 serial port pins use 5V voltage levels, but the Due uses 3.3V voltage levels.

How to Use Additional Arduino Serial Ports

An extra serial port can be used on an Arduino Uno, but must be simulated in software by using the SoftwareSerial library.

Arduino Uno

The following code is taken from the article on serial communications with the GT-511C3 fingerprint scanner which connects the fingerprint scanner to a software serial port on an Arduino Uno.

#include <SoftwareSerial.h>

SoftwareSerial gtSerial(8, 7); // Arduino RX, Arduino TX

void setup() {
  Serial.begin(9600);    // serial / USB port
  gtSerial.begin(9600);  // software serial port
}

byte rx_byte = 0;        // stores received byte

void loop() {
  // check if byte available from USB port
  if (Serial.available()) {
    rx_byte = Serial.read();
    // send a byte to the software serial port
    gtSerial.write(rx_byte);
  }

  // check if byte available on the software serial port
  if (gtSerial.available()) {
    // get the byte from the software serial port
    rx_byte = gtSerial.read();
    Serial.write(rx_byte);
  }
}

To use the software serial port, first the header file for the software serial library must be included.

#include <SoftwareSerial.h>

Next create the software serial port, selecting the Arduino pins to use for receive (RX) and transmit (TX). Here pin 8 has been set as the receive pin and pin 7 as the transmit pin.

SoftwareSerial gtSerial(8, 7);

The software serial port had been given the name gtSerial which will be used in the sketch to refer to this serial port.

The port can now be checked for incoming data.

if (gtSerial.available()) {

If data is available, it can be read from the port.

rx_byte = gtSerial.read();

Data bytes can also be sent on the port.

gtSerial.write(rx_byte);

How to Use Additional Serial Ports on the Arduino MEGA 2560 and Due

The additional hardware ports on the Arduino MEGA 2560 and Due can be used in the same way as the main USB serial port is used in sketches, only changing the name of the port. The USB serial port, or serial port 0 is referred to as Serial in sketches. To use serial port 1, the name changes to Serial1. Serial ports 2 and 3 are referred to as Serial2 and Serial3.

This sketch shows serial port 3 being used which transmits on pin 14 of the MEGA or Due and receives on pin 15.

void setup() {
  // initialize serial ports
  Serial.begin(9600);    // USB serial port 0
  Serial3.begin(9600);   // serial port 3
}

byte rx_byte = 0;        // stores received byte

void loop() {
  // check for data byte on USB serial port
  if (Serial.available()) {
    // get byte from USB serial port
    rx_byte = Serial.read();
    // send byte to serial port 3
    Serial3.write(rx_byte);
  }
  // check for data byte on serial port 3
  if (Serial3.available()) {
    // get a byte from serial port 3
    rx_byte = Serial3.read();
    // send the byte to the USB serial port
    Serial.write(rx_byte);
  }
}

The additional serial ports are immediately available in the sketch without having to include any libraries.

Serial port 3 must first be initialized to the desired baud rate.

Serial3.begin(9600);

The port can be checked for incoming data.

if (Serial3.available()) {

If a byte has arrived on the serial port, it can be read.

rx_byte = Serial3.read();

A byte can be written to the serial port.

Serial.write(rx_byte);

Arduino Serial Port Resources

Arduino Website References for Software and Hardware

Projects, Articles and Tutorials

Using Arduino as a Sports Score Ticker to get Live Cricket Results

An Arduino with Ethernet shield can be configured as an Ethernet client to fetch live sports scores from the Internet. The scores can the be displayed on any display device connected to the Arduino or sent through the serial port.

In the Arduino live cricket score project, the Arduino fetches the live cricket scores from cricbuzz.com and displays them in the Arduino IDE serial monitor window. It gets the scores by accessing the XML scores feed and then extracting the desired information from the XML file.

Arduino cricket score ticker

Arduino Cricket Score Ticker

This is a very early version of cricket score code and will be improved on in the future. The code is susceptible to breaking if there are any unexpected changes to the XML file, but the code will be made more robust and will be updated to handle and recover from errors in the future.

Go to the Arduino live cricket score project →

How to Control an LED from an Arduino Web Page Button and an External Push Button

The article on how to control an LED with both a button on a web page from an Arduino web server and a physical hardware button includes the circuit diagram, HTML and JavaScript code and the Arduino code.

I wrote the article after being asked a question on how to control an LED from an HTML button on an Arduino hosted web page and a physical button connected to an Arduino pin.

The image below shows the final project.

Arduino LED Control from Web Page and Push Button Switch

Arduino LED Control from Web Page and Push Button Switch

An Arduino and Ethernet shield is used with a web page hosted on the micro SD card inserted into the Ethernet shield.

When the checkbox or button on the web page is clicked, the corresponding LED will switch on or off. When a push button is pressed, the corresponding LED will switch on or off and the state of the LED will be updated on the web page. Ajax is used to update the LED states on the web page so that there is no page refresh flicker.

Pressing the left push button causes the left LED to switch on and the checkbox on the page to get a check mark. Pushing the left push button again switches the LED off and the check is removed from the checkbox on the web page.

The button on the web page will initially display the text OFF as part of the button text. When the right push button is pressed, the LED will switch on and the HTML button text will be updated to display ON. Pressing the right push button again will switch the LED off and update the button text on the web page to display OFF again.

Go to the project article with video, circuit diagram and HTML, JavaScript and Arduino Code →