Generally the standard line frequency in some country is 50HZ or in some countries 60HZ, which may vary time to time. Due to this varying nature of frequency, sensitive equipment may start malfunction, and the requirement result we may not get. New here is a simple mains line frequency mater designed and verified at BEP (Best engineering project) lab used to measure the frequency of AC mains.
Circuit description mains line frequency meter
The circuit of mains line frequency mater is build around timer IC2 (NE555), oscillator-cum-driver IC (IC3), decode counter, AND gate IC (IC6), seven segment display and 6 volt regulator IC. The AC mains input (230v) is stepped down using 9v-0-9v step down transformer. The output from secondary winding is rectified by rectifier diode D1 and D2 which further filtered by capacitor C1 and given to input of voltage regulator IC (IC1) to produced regulated 6v DC.
The stepped down 9v is connected to pin 2 and 6 of IC2 (timer IC) for converting the sine wave into square wave frequency.
This converting is done because square wave is more suitable for the circuit operation then sine wave.
The 10HZ clock pulse is generated by IC3 which is wired as oscillator-cum-divider. The outputs 10HZ clock pulse is given to the clock pin 14 of decode counter IC5 (4017).IC5 divides 10HZ clock by 10 to obtain 1 HZ clock pulse. The output of IC3 from pin 3 is again fed into its input pin through VR1 and R4. Capacitor C2 is used as charge/discharge capacitor and is connected between input of IC3 and ground. The value of output frequency from IC3 is depended upon VR1, R4 and capacitor c2, the value of this component is so selected that its output is accurate 10 HZ clock pulse.