Fastest Finger First Electronic Project without using Microcontroller

Now a days quiz-type game shows are increasingly becoming popular on television. In such quiz games, fastest finger first indicators (FFFIs) are used to test the contestant's reaction time. The player’s designated number is displayed with an audio alarm when the player presses his entry button.

Fastest Finger First Project

The fastest finger first circuit diagram presented here determines as to which of the four contestants first pressed the button and locks out the remaining three entries of the other three members. Simultaneously, an audio alarm (buzzer) and the correct decimal number display of the corresponding contestant are activated.

Fastest finger first

Fastest finger first

Components used

  1. Resistors: 1KO, 330O, 100KO, 10O, 10KO

  2. Ceramic Capacitors: 0.033uF, 0.01uF, 0.047uF
    Electrolytic Capacitors: 47uF (35V)

  3. Miscellaneous: Common anode seven segment LED display

  4. S1-S5: Pushbutton (Switches), Speaker (8O, 1W)

  5. Integrated circuits:
    IC 7805     ….voltage regulator
    IC 74LS75 …. 4-bit bistable latch
    IC 74LS20 …. Dual 4 input NAND gate
    IC 74LS147 …. 9 lines to 4 lines priority encoder
    IC 74LS04 …. HEX inverter
    IC 74LS47 …. BCD to seven segment decoder
    IC NE555 …. Timer

Working of Fastest Finger First Indicator:

When a contestant presses his switch, the corresponding output of latch IC2 (7475) changes its logic state from 1 to 0. The combinational circuitry comprising dual 4-input NAND gates of IC3 (7420) locks out subsequent entries by producing the corresponding appropriate latch-disable signal. Priority encoder IC4 (74147) encodes the active-low input corresponding audio oscillator. binary coded decimal (BCD) number output. The outputs of IC4 after inversion by inverter gates inside hex inverter 74LS04 (IC5) are coupled to BCD to-7-segment decoder/display driver IC6 (7447). The output of IC6 drives common anode 7-segment LED display (DIS.1, FND507 or LT542). The audio alarm generator comprises clock oscillator IC7 (555), whose output drives a loudspeaker.

The oscillator frequency can be varied with the help of preset VR1. Logic 0 state at one of the outputs of IC2 produces logic 1 input condition at pin 4 of IC7, the audio oscillator IC7 needs +12V DC supply for sufficient alarm level. The remaining circuit operates on regulated +5V DC supply, which is obtained using IC1 (7805). Once the organizer identifies the contestant who pressed the switch first, he disables the audio alarm and at the same time forces the digital display to ‘0’ by pressing reset pushbutton S5. With a slight modification, this circuit can accommodate more than four contestants.


This project is an electronic quiz buzzer. Fastest finger first indicators are used to test the player's reaction time. The player's designated number is displayed with an audio alarm when the player presses his entry button. In the buzzer round of quiz contest, the question is thrown to all the teams. The person who knows the answer hits the buzzer first and then answers the question. Sometimes two or more players hit the buzzer almost simultaneously and it is very difficult to detect which of the team has pressed the buzzer first. In television shows, where the whole event is recorded, the actions are replayed in slow motion to detect the first hit. Such slow motions are possible only where huge funds are available to conduct the show. For this reason, buzzer rounds are avoided for quiz contests held in colleges.

But this indicator reduces the probability of an error in detecting who pressed the buzzer first. Thus, in this project, we have concluded all the components for the setup of this indicator.

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