[SOLVED] Atmega8 voltmeter hang-up somewhere

[thannara123]

As my part of a project , An Atmega8 based AC 230 voltmeter made ,and works normally .
but some times it hangup or stuck {stuck the LCD display],especially
when toggles [rapidaly connect and disconnect] the input .
what may be the problem .
I am providing some information of the voltmeter

AVCC ---> VCC
Vref connected to capacitor 104 [.1uf]
230 volt ac stepdowned to 6 volt with bridge rectifre ,filtred with 1uf capacitor and finally given to a voltage divider

Some code

int main(void)  
{   
  
     int adc_value1=0;	
	 LCD_Init(2,16);     
    adc_init();
    
     LCD_Clear();
	 LCD_GoToXY(0,0);    
	 LCD_DisplayString("  G-Electron");
	 _delay_ms(1000);
	 
	 //
 	
	while(1)	
	{ 	
       adc_value1 =  volt_read_disply();
	   LCD_GoToLine(1);	 
	   LCD_DisplayString(" Volt : ");  
	   LCD_Printf("%d",adc_value1);
	   LCD_DisplayString("V");  
	   _delay_ms(1300);
	} 
}


int volt_read_disply()
{   int i,adc_value[40]={0}; int temp =0, adc=0;
	
	adc_init();
	  for(i=0; i<=40;i++)                        // samples taking from 41 times 9.4milli second taken about on complte half cycle
	  { 
		 adc_value[i] = read_adc(0);  // reading voltage 		  	  	  
	 }
	  
	 temp = adc_value[0];	 
	for(i=0; i<=40; i++)
	{
		if(temp<adc_value[i])
		temp=adc_value[i];
	}
	adc=temp;			 
		  
      return (adc*0.224828935);	
   
}

 

[baileychic]

variable adc is int type and you are multiplying int value with float value without cating the int value to float or double. You will get 0 readings.

 

[DeepOne]

"for(i=0; i<=40;i++)" must be "for(i=0; i<40;i++)" if adc_value[40]

 

[thannara123]

variable adc is int type and you are multiplying int value with float value without cating the int value to float or double. You will get 0 readings.

Is it correct

 return ((int)temp*0.224828935);

 

[baileychic]

return ((double)temp*0.224828935);

is correct.

 

[betwixt]

Additionally:

int volt_read_disply()

specifies the "volt_read_disply" function returns a value of type 'int' so whatever the result of the fractional multiplication will be lost.

Brian.

 

[thannara123]

Additionally:

int volt_read_disply()

specifies the "volt_read_disply" function returns a value of type 'int' so whatever the result of the fractional multiplication will be lost.

Brian.

Sir are you mean that ,may i need to change the function as Double volt_read_disply() ?

 

[baileychic]

Change return type from int to double and read the adc value into a double type variable and convert it to string and print it on lcd.

 

[betwixt]

Yes, when you prefix a function with a data type, like the 'int' in "int volt_read_disply()" you tell the compiler that it will return an integer value. The compiler then prepares suitable memory storage to carry the value back to where the function was called. If the storage size doesn't match the data you put in it, some will be lost or residual bits will be included.

Depending on the compiler, it should show an error but even if it didn't the value returned from the function would be truncated or misinterpreted.

So answering your question, yes, you should change the function type to double or float.

Brian.