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Make a Digital voltmeter using 16*2 LCD Display interfacing with Arduino uno - KT931

Make a Digital voltmeter using 16*2 LCD Display interfacing with Arduino uno - KT931


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In this tutorial, we are making a Digital Voltmeter using a 16*2 LCD Display with Arduino Uno. It's relatively simple to use an Arduino to measure voltages. The Arduino has several analog input pins that connect to an analog-to-digital converter (ADC) inside the Arduino. The Arduino ADC is a ten-bit converter, meaning that the output value will range from 0 to 1023. We will obtain this value by using the analogRead() function. This project will show you the values up to 5v.

If you know the reference voltage--in this case we will use 5 V--you can easily calculate the voltage present at the analog input. To display the measured voltage, we will use a liquid crystal display (LCD) that has two lines of 16 characters.



Arduino IDE 1.8.5 (programmable platform for Arduino)

Click To Download:



  • LCD Display Mode: STN, Positive, Transflective
  • Display Color: Deep Blue/ Yellow Green
  • Viewing Angle: 6H
  • Driving Method: 1/16 duty, 1/5 bias
  • Back Light: Yellow-Green LED backlight
  • Outline Dimension: 803615.8 MAX


  • The LCD panel is made by glass. Any mechanical shock (e.g. dropping from high place) will damage the LCD module.
  • Do not add excessive force on the surface of the display, which may cause the Display color change abnormally.
  • The polarizer on the LCD is easily get scratched. If possible, do not remove the LCD protective film until the last step of installation.
  • Never attempt to disassemble or rework the LCD module.
  • Only Clean the LCD with Isopropyl Alcohol or Ethyl Alcohol. Other solvents (eg.water) may damage the LCD.
  • When mounting the LCD module, make sure that it is free form twisting, warping and distortion.
  • Ensure to provide enough space (with cushion) between case and LCD panel to prevent external force adding on it, or it may cause damage to the LCD or degrade the display result.
  • Only hold the LCD module by its side. Never hold LCD module by add force on the heat seal of TAB.
  • Never add force to component of the LCD module. It may cause invisible damage or degrade of the reliability.
  • LCD module could be easily damaged by static electricity. Be careful to maintain an optimum anti-static work environment to protect the LCD module.
  • When peeling off the protective film from LCD, static charge may cause abnormal display pattern. It is normal and will resume to normal in a short while.
  • Take care and prevent get hurt by the LCD panel sharp edge.
  • Never operate the LCD module exceed the absolute maximum ratings.
  • Keep the signal line as short as possible to prevent noisy signal applying to LCD module.


The 16x2 LCD used in this experiment has a total of 16 pins. As shown in the table below, eight of the pins are data lines (pins 7-14), two are for power and ground (pins 1 and 16), three are used to control the operation of LCD (pins 4-6), and one is used to adjust the LCD screen brightness (pin 3). The remaining two pins (15 and 16) power the backlight.

Note that the potentiometer is connected to the 5V source and GND and the middle terminal is connected to pin 3 of LCD. Rotating this pot changes the brightness of the LCD. The four data pins DB4-DB7 are connected to the Arduino pins 4-7. Enable is connected to pin 9 of the Arduino and RS is connected to pin 8 of the Arduino. RW is connected to ground. The backlight LED is connected to 5V and ground. The following table shows the pin connections:

DB4 ----->pin4

DB5 ----->pin5

DB6 ----->pin6

DB7 ----->pin7

RS ----->pin8

EN ----->pin9


The program below uses the Liquid Crystal library. This library contains all of the functions needed to write to the LCD.

The loop reads the analog value from the analog input, and because the reference voltage is 5 V, it multiples that value by 5, then divides by 1024 to calculate the actual voltage value. Once the voltage has been calculated, the value is written to the LCD.

Click to see the code or copy the link:


In this project, we will show the voltage of the battery on 16*2 LCD Display and Serial Monitor also using this Digital Voltmeter project. You can verify the values using multimeter available in markets.

Connect the A0 wire to the positive pin of battery and Gnd Wire to the negative pin of battery. The Output will show on the LCD display.

This project will show you the values up to 5v.

In order to measure voltages greater than the 5 V reference voltage, you need to divide the input voltage so that the voltage actually input to the Arduino is 5 V or less. in this experiment, we will use a 90.9 kohm resistor and a 10 kohm resistor to create a 10:1 divider. This will allow us to measure voltages up to 50 V.