Digital Mains Frequency Meter Using Arduino Uno

The design discussed here is a frequency meter. The device uses zero crossing detector, shift registers and seven segment display.

The device measures mains frequency.

The device uses a zero crossing detector. The zero crossing detector gets the time period of the frequency waveform.

The time period is calculated by Arduino Uno and displayed as frequency.

The mains frequency meter is comprised of three parts

a. Zero crossing detector: The zero crossing detector receives sample of the mains frequency signal. It uses a step down transformer to convert 220 V AC mains voltage to 6V AC. This sample voltage is fed to a rectifier and finally fed to an OP AMP. LM324 OPAMP is used in this case.The OPAMP output is fed to PIN 2 of Arduino UNO.

b. Arduino Uno : The heart of the circuit is Arduino Uno. The Arduino Uno uses the following functions

Pulsein: The pulsein() function measures the ON time of the waveform.

duration = pulseIn(pin, HIGH);

We are using Pin 2 as the input PIN.

Shiftout: The shift out function sends data and clock signal to the shift register board.

shiftOut(dataPin, clockPin, MSBFIRST, j[count_1]);

c. Shift registerand display: The shift register part of the circuit consistes serial in parallel out shift registers. We used CD 4094 shift register for the application. The parallel output of the shift registers are connected to therespective seven segments displays.

The circuit is tested and the circuit diagram is attached.