🎵 Digital Musical Note Timer

📘 Overview

The Digital Musical Note Timer is a Logisim-based digital electronics project designed to simulate the timing and sequencing of musical notes using basic digital components such as counters, ROM, comparators, and shift registers.

This project demonstrates how musical note activation can be controlled entirely through digital logic, with each note having a configurable offset (start time) and duration (how long the note plays).

It also incorporates a 10-stage ring counter (built using a shift register) that sequentially activates notes across 10 time slots — simulating a digital rhythm or melody pattern.

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⚙️ System Design

🧩 1. Timing Control Unit

This section manages the precise activation period of each musical note.

• A binary counter continuously increments with the system clock, representing elapsed time.
• The offset and duration inputs (each 4-bit) are user-defined.
• A ROM translates these binary values into corresponding time intervals (e.g., 0–1000 ms).
• Two comparators check:
  • When the counter value equals the offset → note starts playing
  • When the counter exceeds offset + duration → note stops
• The output stays HIGH for the specified duration, lighting up an LED (or triggering a buzzer tone).

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🔁 2. Sequencing & Control Unit

To simulate multiple timed notes, the system employs a 10-stage shift register configured as a ring counter.

• The first stage receives a logic 1 and circulates it through all 10 stages.
• Each stage corresponds to one time slot (e.g., 1 second per stage).
• The ring counter’s output passes through a NOT gate and is combined with the timing logic through an AND gate.
• A third comparator ensures that note activation aligns with the current stage and user-defined timing parameters.
• This setup enables 4 parallel note channels, each capable of playing independently with their own offset, duration, and timing pattern.

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🔧 Components Used

Component	Function
4-bit Binary Counter	Generates time progression
ROM	Converts 4-bit offset and duration inputs into time intervals
Comparators (3 total)	Compare counter values with time intervals
Shift Register (10-stage)	Acts as a ring counter to sequence time slots
Logic Gates (AND, NOR, NOT)	Combine and control activation signals
LEDs (4 total)	Represent musical notes visually
Clock Pulse Generator	Provides the system timing base

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🎶 Functional Flow

1. The counter begins incrementing from zero.
2. The ring counter advances the active stage every clock pulse.
3. The ROM outputs the corresponding offset and duration values for each note.
4. The comparators detect when the counter matches these time ranges.
5. The AND gate combines the comparator outputs and the ring counter signal.
6. The resulting signal lights up the LED, representing an active note.

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🧠 Learning Outcomes

• Practical understanding of sequential and combinational logic design.
• Implementation of timing control using counters and comparators.
• Use of ROM for mapping digital inputs to time values.
• Application of ring counters for sequence generation.
• Integration of multiple digital subsystems into a functional design.

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📊 Circuit Features

• 4 independent note outputs
• 10 time slots controlled by a ring counter
• Adjustable offset and duration for each note
• Modular and scalable architecture
• Fully designed in Logisim

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💡 Future Enhancements

• Connect tone generators or buzzers to produce actual sounds.
• Implement microcontroller integration for programmable note patterns.
• Add variable clock frequency control for tempo adjustment.
• Display active note and timing info on a 7-segment display or LCD.

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🧱 Tools & Platform

• Software: Logisim Evolution
• Language: Digital Logic Design
• Simulation Type: Sequential Circuit Simulation

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