AC voltage to PIC ADC

[markdem]

pic adc

Hi All, I know this question has been asked many times on the forum, but I am still not quite understanding what I need to do.

All I want to do is to measure AC voltage (220VAC) with a PIC.
What I am planning to do is use a transformer to being the voltage down to 7 volts, and then use a resistor divided to bring the voltage down to about 500mV. Then I plan to use an AD737 RMS converter to make the signal DC. I will then pass this on the PIC ADC.

Is this a good way of doing this, or should I try something else?

Thanks, Mark

 

[Guachuchon]

adc pic sine wave

Hi markdem

For measure the AC voltage you can do this procedure using the transformer:


The output of the transformer you must connect to a potentiometer as voltage divider

the output of this you can put into a summer with operational amplifier.
(you can feed this opamp with a single power supply, search the circuits)
you must add a reference voltage for that the output be a sinusoidal wave with 5v peak to peak or less and the minimun voltage be zero volts.

this wave you can connect to PIC (i assume that your PIC have a ADC)

I hope that you can understand this idea and can help you

Regards

 

[Khurram Shahzad]

measuring ac voltage with pic

Hi!
If the voltage you are going to measure is sine wave then:
Use a transformer to step down the voltage. Then convert this AC voltage to DC using a simple op-amp base full wave rectifier. I think it would be easy.

 

[Guachuchon]

ac voltage pic

Hi

The problem with the idea that bring Mr. Khurram Shahzad is that you can't know when the wave is positive or negative because the output of the rectifier is the same wave.

Remember that ADC module of PIC microcontrollers only can work with signals 5v peak to peak and Vref+ is limited for Vcc + 0.3 volts. Vref- is limited for Vdd - 0.3 volts. For more information read the datasheet.

Regards