Measure 330V ac with microcontroller

[A 2]

 I have to measure 300V ac max. I took 330Vrms ac (467V peak) to be on safer. Have to remove opamp for cost reduction which could act as buffer & adder.

Directly put that pin to MCU for measurement by level shifting the signal.

 

1. Divided the ac voltage by two resistors to 2.5V peak or 5V peak to peak.

 

2. planning to level shift this ac signal to 2.5V. So that at MCU adc pin, signal appears as moving from 0-5V. (ac)

 

3. I have attached the circuit. (zoom in to see it)

 

4. But problem is circuit now is on dc bias of 1.455V dc. If we do analysis by superposition, I can find out this.

 

 

But I want to level shift the signal so that it stays on 2.5V dc bias & also appears as low impdence source to analog pin of MCU i.e less than 10K.

What resistor values i should choose

 

 

 

 

[AJISH ALFRED]

The drop in dc bias voltage is due to the parallel effect of R2 and R3 across R5. To avoid this use a significantly high valued resistor for R3, around the range of 100K.

Hope this will solve the issue. Please try and update

[Ashutosh Bhatt]

actually I have posted reply yesterday but is is blocked due to image

 

i have posted circuit of positive clamper using simple capacitor and diode.

 

u can use this circuit to shift level of waveform

[Author]

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