VENDMACH Vending Machine System Design And Testing ✓ Solved

VENDMACH Vending Machine System Design and Testing

Al Ahliyya Amman University جامعة عمان الأهلية project second Semester 2019/2020 Advance Digital System Student Name : Student ID: EP-04-01-F151-Eng, Rev. c Ref.: 31/19 / Date: 09/08/ In addition to these “user” inputs, the machine has two control inputs: CLOCK and INIT. The machine has three outputs: CREDIT, which indicates the amount of money deposited so far and is displayed on the LEFT and RIGHT LED digits; DISPENSED ITEM, which shows the item just purchased on the XS40 LED (g for gum, A for apple, and y for yogurt). The task involves designing, implementing, and testing this vending machine system using Proteus software.

Design and Implementation of the VENDMACH Vending Machine System

Introduction

The VENDMACH vending machine system is a digital electronic system that simulates real-world vending operations. It accepts coins, manages user selections for different items, displays credit, and dispenses the selected product accordingly. The system demands precise logic design, simulation, and testing to ensure proper operation. It combines multiple digital components including coin and selection inputs, counters, combinational logic, and output displays, integrated and tested within Proteus simulation environment.

System Inputs

• Nickel, Dime, Quarter: Signals that become high when respective coins are inserted, contributing 5, 10, and 25 cents respectively.
• CoinReturn: Signal that triggers refund of inserted coins.
• GUM, APPLE, YOGURT: Selection buttons for purchasing the corresponding items.
• CONTROL Signals – CLOCK, INIT: Clock advances the system state; INIT resets the system.

System Outputs

• CREDIT: Displays current total in cents, on 2-digit LED display.
• Dispensed Item: The item just bought appears on XS40 LED, represented as 'g', 'A', or 'y'.

System Design Steps

1. Coin Processing: Use digital circuits to add the coin values to a credit register, updating with each coin insertion. Detections of DIME and QUARTER should properly add 10 and 25 cents respectively, while NICKEL adds 5 cents.
2. Credit Management: Implement a 7-bit or more binary counter to store the current credit, resetting on INIT or when coins are returned.
3. Item Selection and Pricing: Each item's price (gum: 15¢, apple: 20¢, yogurt: 25¢) is checked against current credit. Selection buttons trigger checks and either dispense the item or ignore if insufficient credit.
4. Dispensing Logic: When credit >= item price, activate the output that shows the item on the LED and deduct the price from credit. If not, no item is dispensed.
5. Coin Return: When pressed, refund current credit and reset the credit register.
6. Display Logic: Continuous updating of the CREDIT display and showing the dispensed item on XS40 LED when applicable.

Implementation in Proteus

The design utilizes digital components including counters, multiplexers, logic gates, flip-flops, and display drivers. Using Proteus, the circuit is assembled with these components interconnected as per the logic design. The coin inputs are simulated with push-buttons or switches, while outputs are connected to LED displays and 7-segment modules for visual feedback. The system is tested through simulation by inserting various coins, making selections, and observing outputs to verify correct credit updates, item dispensing, and reset functionality.

Testing and Validation

Initializations are performed with the Init signal, ensuring reset operation. Coins are added sequentially, and the credit is monitored to ensure it updates correctly (adding 5, 10, or 25 cents accordingly). Selection buttons are pressed to attempt purchases with sufficient or insufficient credits, verifying that items are dispensed only when credits cover item prices, and that the displayed item and credit change are accurate. Coin return is tested to ensure refunds are processed properly. The system's response to rapid coin insertions and multiple selections demonstrates robustness and correctness. The simulation confirms the system's capability to emulate a real vending machine behavior comprehensively.

Conclusion

The design and simulation of the VENDMACH vending machine in Proteus validate the system’s functionality to accept coins, manage credit, process user selections, dispense items, and handle refunds effectively. Through logical circuitry and careful testing, the project ensures that the implementation aligns with real-world vending operations, providing a fundamental understanding of digital system design. Proper testing confirms accuracy in credit management, item dispensing, and user interactions, making the system a practical educational tool in digital system design courses.

References

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