A Voltmeter is a pivotal equipment for any electronic project and its prominence is associated with the measurement of both AC and DC voltages. It is an instrument used for measuring voltage or potential difference between two points in a circuit. Among two types of voltmeters, i.e. Analog and Digital, the later one provides almost error free measurement and display measured voltage numerical in digital manner. This project by electronics hub aims to design an Arduino based Digital Voltmeter which can measure voltages up to 50V. 

 

 

The components used in this project includes Arduino UNO, 16 x 2 LCD Display, 10KΩ POT, 100KΩ and connecting Wires. For this project, two circuits are designed, where the former one is used for measuring voltages less than or equal to 5V and the latter is used for measuring voltages up to 50V. While the LCD used is same for both the circuits.

 

Pin 1 and 2 of the LCD power supply are used for display and are connected to ground and +5V supply respectively. While Pin 3 is used for the contrast adjustment of the display and is connected to the wiper terminal of the 10KΩ POT. Control pins of the LCD are connected to digital input/output of Arduino and to the ground.

 

The data pins of the LCD uses 4-bit data mode and hence pins are connected to digital input/output pins of the Arduino. Pins 15 and 16 are used as the supply pins of the backlight LEDs and are connected to +5V supply through a current limiting resistor of 220Ω and to the ground respectively.

 

 

The first circuit has no additional connections, therefore voltage is measured by establishing connection directly to the analog input A0 of the Arduino UNO. While the second circuit requires additional connection to a voltage circuit, consisting of 100KΩ resistor and 10KΩ resistor. Arduino and the ground terminal of the input voltage remains common to both circuit.

 

The voltage measured in this digital voltmeter is converted from analogue to digital form with the help of Analog to Digital Converters (ADC). The input voltage of first circuit is transferred to the analog input pin of the Arduino. Since the voltage ranges for Arduino UNOs analog input is 0V to 5V, a voltage divider circuit is used to increase the range.

 

The range of the analog input of Arduino UNO in the second circuit can be increased up to 50V by using a voltage divider. It comprises of 100KΩ resistor and 10KΩ resistor, which helps to match the input voltage to the range of Arduino UNOs analog input. And other calculations are carried out by the programming part of the Arduino UNO.