need help to measure ac voltage and current

[eng_mahmoud87]

i need to measure ac current and voltage by microcontroller PIC16f877 (A/D) but this A/D can measure until 5v so i need circuit to make scale between 5 v and 24 v and thanks alot

 

[IanP]

A simple resistive voltage divider should work ..
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/voldiv.html
To ensure that the voltage fed to the PIC's pin never exceeds 5V add 5.1V zener diode between this pin and GND ..

Regards,
IanP

 

[hassenman]

Hi eng_mahmoud87,

This is very simple, u can use a simple resistors divider to measure the voltage .
Concerning the current, u will have to measure it by measuring the voltage across a resistor and manage to do the math with your soft.

Hope this helps,
regards,
Hassen.

 

[max0412]

Good app note from Zetex might give you some ideas.

http://www.zetex.com/3.0/appnotes/apps/an39.pdf