• Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Get free circuit help 24/7

  • Circuits for Beginners
  • Basic Circuits
  • Hobby Projects
  • Transistor Circuits

New-Projects | Privacy Policy | About us | Contact | Disclaimer | Copyright

Home » Fun Projects » 2 Simple Fastest Finger First Circuits Explained

2 Simple Fastest Finger First Circuits Explained

Last Updated on February 29, 2020 by Swagatam 6 Comments

The 2 simple fastest finger first indicator circuits presented here can be used for indicating which candidate was the first to press the answer button out of the 4 participating candidates in a quiz contest.

We all have probably seen the famous game show "who wants to be a millionaire" and many similar quiz shows, where in the initial stages a few of the participants are asked to go through a small test, the participants are asked a question, and the member who answers it first by pressing the buzzer is given the opportunity to occupy the "hot seat".

Well everybody might not be as lucky to get into such game shows, but you can certainly enjoy making and playing with this little fastest finger first decider circuit right in your home.The circuit is very simple, utilizes just a couple of ICs and some LEDs.

Design #1 using IC 74122

In a 'professional' quiz game set up, we may require some form of electronic detector for accurately detecting the fastest candidate pressing the buzzer button and the first candidate to answer an asked question.

The simple fastest finger first circuit using IC 74122 shown below is designed to implement the proposed task.

Circuit Description

Push-button S5 is one button that is controlled by the quiz master.

As long as the quiz master keeps this button depressed, all the LED indicator stages remain disabled. The moment he releases S5 all the remaining circuits and the associated press buttons become active.

The candidate who presses one of the assigned buttons (S1-S4), it triggers the monostable (IC1 -IC4) stage connected with that button.

The monostable switches ON the respective indicator LED and at the same time blocks the other three monostables by means of N1.

The period for which the monostables remain disabled is around 8 seconds, after this delay the indicator lamp switches OFF allowing the other candidates to resume the fastest finger first game. The quiz master has the power to reset all monostables whenever he wants it, or when it is essential to 'override' button S5.

Design #2 Using IC 7475

In the second design four push-to-ON type of switches are placed at the input of the IC 7475 which is a 4-Bit Bistable Latch with Complementary Outputs.

The button which is pressed first, triggers the relevant output of the IC 7475, which in turn prompts the IC 7420 to instantly deactivate the other inputs from the other push buttons, rendering the whole system inactive, except the one which had the first trigger through the push button.

This output concerning the triggered latch illuminates the relevant LED, indicating the button number which was pressed first.

The is a simple game circuit which can be built by all electronic hobbyists and also school kids.

Pinout Details of IC 7420

You'll also like:

  • 1.  Simple 1.5 V Inductance Meter Circuit
  • 2.  Simple Ultrasonic Sound Sensor Alarm Circuit using Opamp
  • 3.  Simple MOSFET Tester and Sorter Circuit
  • 4.  Simple LPG Gas Detector Alarm Circuit
  • 5.  2 Simple Voltage to Frequency Converter Circuits Explained
  • 6.  Simple Touch Operated Potentiometer Circuit

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

Subscribe2


 

Reader Interactions

Comments

    Your Comments are too Valuable! But please see that they are related to the above article, and are not off-topic! Cancel reply

    Your email address will not be published. Required fields are marked *

  1. Hid Per says

    Hi friend
    Nice and simple circuit, the “SECOND”…
    i would like to make it…
    But i cannot the numbering connection of IC 7420 to others?

    greetings ヅ

    Reply
    • Swagatam says

      Thanks friend, I have updated the pinout details of the IC 7420 at the end of the post, you can connect them accordingly.

      Reply
  2. Hid Per says

    HI

    Hi friend
    Could this combinations below be correct?
    (7420) 1-2-4 to 8 (7420)
    (7420) 5 to (reset button)
    (7420) 6 to 13-4 (7475)
    (7420) 9 to 9 (7475)
    (7420) 10 to 10 (7475)
    (7420) 12 to 15 (7475)
    (7420) 13 to 16 (7475)
    Great thanks ヅ

    Reply
    • Swagatam says

      Yes that looks OK to me.

      Reply
  3. Yedan says

    could you modify this design to work with sound as an activator not a push button, im looking to create a “who fired first” for quick draw shooting so need a system that will pick up the bang of the first gun to fire and light its light disabling the opponents light, then auto reset after say 15sec.

    Reply
    • Swagatam says

      Yes that may be possible. You will need 4 separate sound activated relay circuits, and then integrate the relay contacts with the relevant push switch contacts.

      You can try the following sound activated relay circuit as an example:

      https://www.homemade-circuits.com/wp-content/uploads/2022/04/clap-switch-staircase-lamp.jpg

      Please ignore the LED bulb and its associated wiring.

      Reply

Primary Sidebar

Categories

  • 3-Phase Power (15)
  • 324 IC Circuits (19)
  • 4017 IC Circuits (53)
  • 4060 IC Circuits (25)
  • 555 IC Circuits (98)
  • 741 IC Circuits (19)
  • Amplifiers (58)
  • Arduino Engineering Projects (82)
  • Audio Projects (94)
  • Battery Chargers (82)
  • Car and Motorcycle (94)
  • Datasheets (46)
  • Decorative Lighting (Diwali, Christmas) (33)
  • DIY LED Projects (89)
  • Electronic Components (97)
  • Electronic Devices and Circuit Theory (35)
  • Electronics Tutorial (109)
  • Fish Aquarium (5)
  • Free Energy (35)
  • Fun Projects (11)
  • GSM Projects (9)
  • Health Related (18)
  • Heater Controllers (28)
  • Home Electrical Circuits (101)
  • How to Articles (20)
  • Incubator Related (6)
  • Industrial Electronics (28)
  • Infrared (IR) (40)
  • Inverter Circuits (98)
  • Laser Projects (12)
  • LM317/LM338 (21)
  • LM3915 IC (25)
  • Meters and Testers (62)
  • Mini Projects (172)
  • Motor Controller (66)
  • MPPT (7)
  • Oscillator Circuits (24)
  • PIR (Passive Infrared) (8)
  • Power Electronics (33)
  • Power Supply Circuits (74)
  • Radio Circuits (9)
  • Remote Control (47)
  • Security and Alarm (61)
  • Sensors and Detectors (116)
  • SG3525 IC (5)
  • Simple Circuits (75)
  • SMPS (29)
  • Solar Controllers (61)
  • Timer and Delay Relay (54)
  • TL494 IC (5)
  • Transformerless Power Supply (8)
  • Transmitter Circuits (40)
  • Ultrasonic Projects (14)
  • Water Level Controller (45)

Circuit Calculators

  • AWG to Millimeter Converter
  • Battery Back up Time Calculator
  • Capacitance Reactance Calculator
  • IC 555 Astable Calculator
  • IC 555 Monostable Calculator
  • Inductance Calculator
  • LC Resonance Calculator
  • LM317, LM338, LM396 Calculator
  • Ohm’s Law Calculator
  • Phase Angle Phase Shift Calculator
  • Power Factor (PF) Calculator
  • Reactance Calculator
  • Small Signal Transistor(BJT) and Diode Quick Datasheet
  • Transistor Astable Calculator
  • Transistor base Resistor Calculator
  • Voltage Divider Calculator
  • Wire Current Calculator
  • Zener Diode Calculator

Facebook
Twitter
YouTube
Instagram
My Facebook-Page
Quora

© 2022 · Swagatam Innovations

We use cookies on our website to give you the best experience.
Cookie settingsAccept All
Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Please visit the Privacy Policy Page for more info.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Non-necessary
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
SAVE & ACCEPT