Simple Digital Voltmeter (DVM) using PIC16f877A (Code+Proteus simulation)

 PIC16F877A based volt meter 

This post provides a simple digital voltmeter circuit using PIC16f877A microcontroller. This code is written in C language using MPLAB X IDE with XC8 compiler. 

In this post, it is assumed that you know,

• How to use ADC of PIC16F877A microcontroller. 
• How to interface LCD with PIC16F877A microcontroller. 

Figure 1.   Digital voltmeter using PIC16F877A

In this circuit PORTB pins are used to interface LCD with PIC167877A microcontroller. The input to the digital voltmeter is given on the RA0 (or AN0) pin.

You cannot feed a 20V signal directly to a PIC microcontroller’s input channel. It is too higher than its operating voltage, and the microcontroller could be damaged. So, first we need a voltage scaler that will scale down the input voltage to the safe operating voltage range of PIC16F877A. It can be achieved by a simple resistor divider network shown in the below Image.

Figure:2 Voltage divider network

Using two resistors, R1 and R2, the input voltage ranging from 0-20V can be down

converted to 0-5V.

Calculation:

Voltage Divider Network:

Vout = Vin * R2 / R1+R2

Here Vin =13,R1=470K and R2=200k

Vout = 13*(200+670);

Vout = 13*(0.29850);

Vout = 3.88 volts;

ADC :

0 – 5 V Analog I/P is mapped to one of the 1024 levels (0-1023 Digital Count)

=> Resolution = 5/1024 = 0.00488 V/Count

Volt = ADC_Result * 0.00488 * 0.29850; 

Coding:

Figure 3: Pic16f877A voltmeter code

Downloads:

Digital voltmeter code using PIC16F877A was compiled in MPLAB X IDE v3.05 with XC8 V1.34 compiler and simulation was made in Proteus v7.10. To download code and Proteus simulation Click here.