Help scaling voltage...

[mackrackit]

Forget the opamp. The thread was talking about using a simple voltage divider to scale the signal voltage down to PIC level. If you have 6 volts use a 1 to 1 voltage divider to make 3 volts. Set the ADC reference voltage to see full scale (apply 6 v to divider ADC out put 255) and you should be good to go.

[sirvo]

Forget the opamp. The thread was talking about using a simple voltage divider to scale the signal voltage down to PIC level. If you have 6 volts use a 1 to 1 voltage divider to make 3 volts. Set the ADC reference voltage to see full scale (apply 6 v to divider ADC out put 255) and you should be good to go.

I totally agree with you. But maybe I forgot to explain something that, unfortunatelly, I am not sure. My car fuel sensor is a voltage divider, I think. The sensor is a variable resistor and its range is from 40 to 280 ohms and it turns that the voltage range, as I said, is from 0 (1,66V) to 6V. If I use a simple voltage divider in this fuel signal, will not it change the signal that is being send to the car? That is the reason why I am using the opamp as a buffer..

Thanks again..

[Darrel Taylor]

The LM324 can only reach VDD -1.5V. So with 5V powering it, the most you can get out is around 3.5V.

If you power it with 7.5 V or more, it'll give you the full range.
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[sirvo]

The LM324 can only reach VDD -1.5V. So with 5V powering it, the most you can get out is around 3.5V.

If you power it with 7.5 V or more, it'll give you the full range.
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Thanks Darrel. You are so correctly! i have just experimented that and it worked!

Thanks again.

Sylvio