4-bit Calculator

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Congratulations! You have reached the final project of Module 4.

In previous exercises, you built an Adder (which speaks Binary) and a Decoder System (which speaks Human/Decimal). Now, you will combine these separate subsystems into a complete 4-Bit Calculator.

Project Objective: Build a circuit that accepts two 4-bit binary numbers via switches, adds them together, and displays the decimal result (0-30) on two 7-segment displays.

1) System Architecture

Our calculator works in three simple steps:

  1. Add the Numbers (The Adder): We use the 74LS283 chip to add the binary numbers from your switches. It outputs the result in binary (like 11110 for 30).

  2. Translate to Decimal (The Converter): We cannot read raw binary easily. Use the circuit that you have created in Exercise 3 for converting binary to BCD and then to a seven segment display output.

2) Step-by-Step Build

First, we need to perform the math.

  1. Place the 74LS283 Adder on your breadboard.
  2. Connect Inputs A_1-A_4 and B_1-B_4 to your DIP switches. Remember to include pull-down resistors.
  3. Important: Ground the Carry In (C_0) pin.
  4. Test: Connect temporary LEDs to the Sum outputs (S_1-S_4) and Carry Out (C_4). Verify that 1+1=2 (binary 0010). Once verified, remove the LEDs but keep the wires ready.

What is the maximum possible number we can calculate? (Input A = 15, Input B = 15)

Next, we connect the outputs to the display unit we built in the previous exercise.

  1. Remove the DIP switch and pull-down resistors from the input of the display module.
  2. Connect the S_1-S_4 outputs to the B_0-B_3 inputs of the display module.
  3. Connect the C_4 output of the adder to the B_4 input of the display module.
  4. Connect the B_5 input of the display module to GND.
  5. Finally, connect the two circuits' power lines together.

3) Final Testing

Power up your circuit! If all connections are correct, the displays should show "00".

Test Cases:

  1. Simple Addition: Set A=1, B=2. Display should read 03.
  2. Crossing 9: Set A=5, B=5. Display should read 10. (This proves the Tens digit logic works).
  3. Maximum Value: Set A=15 (all on), B=15 (all on). Display should read 30.

Troubleshooting: You set A=5 and B=5, but the display reads '0A' (or a weird symbol) instead of '10'. What is likely missing?

4) Final Project Submission

This is the big one! Show us your fully operational calculator.

Upload a video demonstration (20-30 seconds). Start with the display at 00. Perform the calculation 7 + 8 = 15. Then perform 15 + 15 = 30. Ensure the digits are readable.
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In the next module, you will dive deeper in to binary arithmetics, and learn about advanced binary arithmetics including accumulation and binary subtraction!