Tag Archives: ac

AC Current Measurement using ACS712

The ACS712 measures current in two directions.  It means that if we sample fast enough and long enough, we sure to find the peak in one direction and the peak in another direction as the ACS712 have 5 μs output rise time in response to step input current. We are measuring AC current of 50Hz i.e. 20mSec per cycle and we get around 4000 Samples in one cycle.

With both peaks known, it is a matter of knowing the shape of the waveform to calculate the current.   In the case of line or mains power, we know that waveform to be a SINE wave.   Knowing that allows us to apply a basic electronic formula to yield a decent result.

RMS Current =  root(2) * Peek Current Continue reading AC Current Measurement using ACS712

AC Voltage Measurement using Arduino

AC voltage measurement can be carried out by converting AC voltage into proportional DC Voltage using rectifier and filter circuits. For low AC voltage (mili volts) measurement precision rectifier is used as diode knee voltage is 0.7 Volt. Similar to DC voltage measurement Voltage divider is constructed using 47K Ohm variable resistor R1. 5V zener diode is used to protect Arduino from accidental excess voltages. Adjust the resistor R1 (47K) to calibrate the voltage. Here the AC voltage that we can give to transformer is from 50V to 230V depending on its ratings. Rectified DC is fed to the voltage divider circuit. Continue reading AC Voltage Measurement using Arduino