Quiz Buzzer System

A 4-player digital buzzer circuit built in Logisim Evolution. Whoever presses their button first gets locked in and their LED lights up — everyone else is locked out until reset. A countdown timer starts once a player buzzes in, giving them a limited time to answer before the circuit auto-resets for the next question.

Features

• 4 independent player inputs (P1–P4), each with a dedicated LED
• First-press priority logic: the first player to press locks out the other three
• Manual Reset: quizmaster button clears all latches for the next round
• Countdown answer timer: once a player buzzes in, a 4-bit countdown starts (via My_Counter subcircuit + 7-segment display); when it expires, the circuit auto-resets — no manual reset needed if the player doesn't answer in time

Tech Stack

• Logisim Evolution (v4.1.0)
• Digital logic: AND Gates, D Flip-Flops (used as SR Latches), T Flip-Flops (counter), 7-Segment Display

How It Works

Buzzer / priority logic: each player's button feeds an AND gate. If no one has pressed yet, the gate fires and sets that player's SR Latch (built from a D Flip-Flop, using only S/R — D and CLK left unconnected), lighting their LED. The latch's Q' output feeds back into the other three AND gates as a block signal, so any later press is ignored until reset.

Countdown timer (My_Counter): a 4-bit counter built from 4 T Flip-Flops in series, sharing a common clock and Reset line. Once a player is locked in, the counter starts counting down, driving a 7-segment display so the quizmaster can see the remaining time. When the count reaches its limit, it triggers a Reset pulse that clears the SR latches automatically — same effect as the quizmaster pressing Reset manually.

Project Structure

Quiz-Buzzer-System/
├── 4p_Quizz_Buzzer.circ         # Main Logisim project (buzzer logic + counter subcircuit)
├── docs/
│ ├── Report.pdf                 # Original academic report (see note below)
│ └── images/
│   ├── Diagram.png              # Full circuit diagram (buzzer + counter + display)
│   └── My-Counter.png           # T Flip-Flop countdown counter subcircuit diagram
└── README.md

Getting Started

1. Install Logisim Evolution (v4.1.0 or later).
2. Clone this repo and open 4p_Quizz_Buzzer.circ.
3. Run the simulation (main circuit).
4. Press any player button (P1–P4) — that player's LED lights up, and the countdown timer starts on the 7-segment display.
5. Press RESET to manually clear the round, or let the countdown expire for an automatic reset.

Notes

This project was built for the Digital Design Lab [ECOM 1101] course at the Islamic University of Gaza (Faculty of Engineering, Computer Engineering).

📄 docs/Report.pdf documents an earlier version of this project — the core buzzer/priority logic (AND gates + SR latches) is the same, but that report was written before the countdown timer (My_Counter) feature was added. It's included for academic context (design decisions, truth table, components table), not as documentation of the current final circuit.

License

No license specified yet.