Hi! ADC reading problem

[Amali_SL]

I want to make a voltage monitor circuit. 0V to 2.5V LED on and 2.5V to 5V LED off .When I test with Proteus this circuit works well. But practical circuit, analog input pin cannot get to zero volts. It’s always show about 2V. From 2v to 5v range works. I disconnect analog input pin and measure voltage but it’s not zero (Show about 2.5v).
What’s the problem? Please help me.

void main() {
unsigned int read;
ANSEL=0x28;
CMCON=7;
ADCON0=0x0F;
TRISIO=0x10;
GPIO=0x00;
while(1){

read=ADC_Read(3);
if(read>510){
GPIO.B0=0;
}
if(read<510){
GPIO.B0=1;
}

}
}

 

[sreepss]

Which controller you are using? Please Specify that.. The TRIS resister should be configured as input. and configure analog mode and it never give an out put voltage of 2V!!!!.. Check your circuit.. And also check grounds of the connection.

 

[Amali_SL]

Which controller you are using? Please Specify that.. The TRIS resister should be configured as input. and configure analog mode and it never give an out put voltage of 2V!!!!.. Check your circuit.. And also check grounds of the connection.

Thanks for reply.
I’m using 12F675.

When I disconnect ADC pin, but still has about 2.5V that pin. Why?

 

[dimas_lilik]

did you share true schematic that you made? i think your trouble about ground of connection.