I need help in the following assignment
13.1. Objectives
Students will design and simulate a secure access control system using combinational logic circuits and sequential circuits.
This project challenges students to create a digital system capable of validating a 4-digit security code entered via a keypad
and granting access upon successful authentication. The open-ended nature of the lab allows for flexibility in design and
encourages creativity.
13.2. Task Description
13.2.1. Design a Secure Access Control System
The system should include:
• Code Storage Logic: Use a set of DIP switches to store the 4-digit code in memory.
• Keypad Input Processing: Convert keypad inputs to BCD for comparison.
• Code Verification Logic: Compare the entered code with the stored code.
• Output Activation: Provide an output signal to open the secured door or gate if the entered code matches the stored
code.
13.2.2. Implement Core Components
• Combinational Logic: Encode keypad inputs into BCD, generate control signals for the state machine, and design
the comparison logic.
• Sequential Circuits: Use flip-flops or registers to store the entered code and sequence through the input stages.
• State Machine: Manage the sequence of operations, such as setting up the system, entering the code, and verifying
the code.
13.2.3. Simulation Platform
• Choose between Multisim or Proteus for designing and testing the circuit.
• Use components such as DIP switches, a keypad module, BCD encoders, registers, comparators, and logic gates.
13.2.4. Innovation and Creativity
Explore different approaches for enhancing the system, such as:
• Adding a lockout mechanism after three failed attempts.
• Implementing a feature to reset the stored code.
• Displaying feedback on an LCD (e.g., “Access Granted” or “Invalid Code”).
13.3. Guidelines for Implementation
13.3.1. Understand the Problem
• Identify the stages of operation: code setup, input, comparison, and access control.
• Break the system into smaller modules for easy implementation.
13.3.2. Plan the Design
• Sketch a block diagram outlining how combinational and sequential circuits will interact.
• Decide how to handle inputs, outputs, and transitions between states.
• Assign responsibilities within the team for specific modules.

13.3.3. Build and Test
• Test individual modules (keypad encoder, code comparator) in isolation before integrating them.
• Debug and refine the design based on simulation results.
13.3.4. Document the Process
• Record the design decisions, challenges faced, and how they were resolved.
• Include simulation results and screenshots to support your final design.

 

Hi HM,
As this is a college assignment, please post your best attempt at answering, we can then help.

Moderation

 

Hi HM,
As this is a college assignment, please post your best attempt at answering, we can then help.

Moderation

i have shortlisted the following components for the circuit

• 4x4 Keypad: For user's input.
• DIP Switches: To store the predefined code.
• BCD Encoder (74LS147): Convert the keypad's input into 4-bit binary.
• Flip-Flops (74LS74): To store digits entered by the user.
• Comparator (74LS85): To compare the stored codes and the entered codes.
• Logic Gates: XOR gates for building a custom comparator etc.
• Output Indicators: LEDs as output indicators.

 

I was building a circuit diagram before on multisim but i got lost mid ways then I came up with the above components this is what i had before

 

i would really appreciate any kind of help

 

I am an educator in electronics. Personally, I find this assignment to be totally unreasonable. It is much too complex to implement with standard combinational and sequential digital logic.

 

I am an educator in electronics. Personally, I find this assignment to be totally unreasonable. It is much too complex to implement with standard combinational and sequential digital logic.

Possibly. That was my initial impression. But as I looked at it a little more closely, I'm not so sure that it is really that large or complex. It also appears to be a semester wrap up assignment, probably with several weeks allocated for it. They specifically guide the student to design and test it in modules, which should help.

 

We aren't given weeks for the assignment. We have just 2 weeks until the deadline and other projects alongside this isn't even the wrap up assignment its just the open ended lab the wrap up assignment is still to be given in the coming week. I'd really appreciate any help.

 

hi HM.
A couple of points with ref to your posted circuit,

What do you expect to happen when you press the S1 switch?

Also, how did you decide the pull-down resistor of 10K.

Post your notes or a flow chart, if you have one, on how you see the circuit operating.

E