analog high speed input to uc

[Disha Karnataki]

hi everyone,
i am trying to give a stepped down ac voltage to the pins of 8051 uc and measure the voltage applied .Where i am wondering whether uc will accept the variable voltage (as it will consider logic 1 for all voltage levels above ttl) so in ac waveform if the voltage goes below ttl logic(as in negative half cycle) then will there won't be a mess up.
i am totally confused please help me in detailed way as i'll be applying the logic explained here even to implement to measure current.
I have here only the confusion of how will the uc accept high speed inputs not about the programing part..:?:[/B]

 

[Genovator]

No pins of 8051 can accept analog voltages. So you need an adc converter. If it is a matter of reading the applied voltage only, then why don't you rectify the supply. This way you can rule out the negative half cycle... Use a rectifier & a good filter, convert it in dc, read through adc, multiply by 44( if step down is 220v - 5v) & divide by 1.414. You will get the rms voltage.
And 50Hz is not a high speed...

You can search in google about '8051 voltmeter' and also refer to this link..
https://www.circuitstoday.com/voltmeter-using-8051

 

[Disha Karnataki]

hey genovator,
no matter i don't require it to when measuring the voltage. but, i do require it while i am measuring power factor.