PIC18F4550 ADC Simple Digital Volt Meter

The ADC module of PIC18F4550 could read an analog input voltage up to 5 V DC with some DC offset. However, the outside analog voltage fed to the ADC could be greater than 5 V DC by adding a simple voltage divider circuit. 

x2

x1.5

x1

x0.5

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The voltage divider circuit is very simple, built by two resistors in this case. The output voltage from the divider circuit is smaller than the input according to the dividing factor. The factor created by picking up a different resistances of the selected's. The designer may decide and take a little math calculation using voltage divider theorem to get a specific division factor. 

I don't show the overall process of math calculation here. You can see this post to get a full detail.

The MCU reads the analog input voltage fed to RA0.

PICC Source Code

	#include<18f4550.h>
	#device ADC=10
	/*Use high speed clock no PLL prescaler
	no system clock post scaler */
	#fuses HS,PLL1,CPUDIV1
	#use delay(clock=20M)
	#define LCD_ENABLE_PIN PIN_B2
	#define LCD_RS_PIN PIN_B0
	#define LCD_RW_PIN PIN_B1
	#define LCD_DATA4 PIN_B4
	#define LCD_DATA5 PIN_B5
	#define LCD_DATA6 PIN_B6
	#define LCD_DATA7 PIN_B7
	#include<lcd.c>
	void adcConfig(void){
	//RA0 As Input
	set_tris_a(0x01);
	//Set RA0 To Analog
	setup_adc_ports(AN0);
	//Select ADC internal RC Clock
	setup_adc(ADC_CLOCK_INTERNAL);
	set_adc_channel(0);
	delay_ms(10);
	}
	float getVoltage(void){
	int16 analogValue=read_adc();
	while(!adc_done());
	float voltage = (analogValue*5.0)/1024;
	/*Voltage Divider*/
	voltage*=0.11;
	/*Scale Up*/
	voltage*=100;
	return voltage;
	}
	void main(){
	float voltage;
	lcd_init();
	adcConfig();
	while(1){
	lcd_gotoXy(1,1);
	printf(LCD_PUTC,"Voltage Reading");
	lcd_gotoXy(1,2);
	voltage=getVoltage();
	printf(LCD_PUTC,"%0.2f Volts ",voltage);
	delay_ms(250);
	}
	}

view raw simpleDvm.c hosted with ❤ by GitHub

Schematic Diagram

Schematic Diagram

Click here to download the zip file of this example.

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