Frequency counter

Frequency counter

By kacheung chan

This was a electronic experiment aims to build a frequency counter from upto 9khz.

The components used are as follows:Resistor: 620×1, 820k×1, 3k×1, 500×1, 220×1, 200kpreset×1Capacitor: 0.1uF×5, 1uF×5, 0.47uF×1Semi conductor: 74LS390×2, 74LS75×4, 74LS47×4, 74LS132×1, 74LS08×1,  LM555×1, zener diode: 6v2×2, LED×1

This circuit is composes of three parts which are timebase and input circuit, Counter logic 1and 2, and the display unit.

Within the timebase circuit, 555 generateca 1second pulse signal and then compare to the input signal by 132b.

It finally enter to pin1 of 74LS390 as it input signal to be duel with.The duty of 74LS390 is to change decimal signal to binary signal. There are ripple counters inside. The 4 bits binary signal through pins 3,5,6,7 and 9,10,11,13 are sent to 74Ls75 larch for simultaneous action with clock signal by 555. While the clock is enable, the latched 4 bits signal will refer to 74LS47 Which is a decoder changing binary signal to the display leds that show the real decimal number.