Experiment - 5

Summary

In this experiment, you will wire a circuit to display binary numbers on two seven-segment displays. It covers testing key components such as the 74 LS 85 comparator, 74 LS 83 adder, and 74 LS 47 BCD to 7-segment driver. The experiment includes step-by-step instructions for wiring inputs, verifying outputs, and using a voltmeter for testing. Additionally, it demonstrates how to display binary inputs on seven-segment displays, ensuring the proper functionality of each component. The process concludes with a demonstration of the final output, where the circuit successfully displays the binary result of the comparator's output.

Takeaways

• 😀 The experiment involves wiring a circuit to display a binary number on two seven-segment displays.
• 😀 The comparator (74LS85) compares two 4-bit binary numbers (A and B) and outputs signals based on whether A is greater than, equal to, or less than B.
• 😀 A common power rail is used in the experiment, with a separate ground rail for easy switching between 1 and 0 voltages.
• 😀 The comparator inputs should be carefully wired to ensure the correct logic for greater than, equal to, or less than outputs.
• 😀 When testing the comparator, the voltmeter is used to check the output signals at the correct pins, ensuring proper functionality.
• 😀 The adder (74LS83) adds two 4-bit binary numbers, with inputs A4-A1 and B4-B1, and outputs the sum and carry.
• 😀 For the adder, the input carry (C0) should be grounded, and the sum and carry outputs need to be verified using a voltmeter.
• 😀 The BCD to 7-segment driver (74LS47) converts a BCD input to drive a seven-segment display, lighting up the appropriate segments to show a decimal digit.
• 😀 The seven-segment displays used are common anode displays, and appropriate current-limiting resistors should be used to prevent damage to the LEDs.
• 😀 Once all components are tested individually, the final circuit configuration should display the correct decimal numbers on the two seven-segment displays based on the comparator's output.
• 😀 Changes in the comparator's input will reflect on the seven-segment displays, updating the output number as expected (e.g., switching from 12 to 4).

Q & A

What components are required for this experiment?

The components required are a comparator (74 LS 85), an adder (74 LS 83), a 7-segment driver (74 LS 47), and two 7-segment displays.

How does the comparator (74 LS 85) work?

The comparator compares two 4-bit binary numbers (A and B). It outputs three signals: 'A > B' (pin 5), 'A = B' (pin 6), and 'A < B' (pin 7), which indicate the result of the comparison.

What is the importance of tying the inputs 'A > B', 'A = B', and 'A < B' to 0, 1, 0?

Tying the inputs to 0, 1, 0 ensures that the comparator functions correctly and can provide valid outputs based on the comparison.

Why is it important to color-code the input wires in this experiment?

Color-coding the wires (e.g., yellow for MSB and green for LSB) helps to easily identify and manage the inputs, reducing the chance of wiring errors.

What does the adder (74 LS 83) do in this circuit?

The adder takes two 4-bit binary numbers (A and B), computes their sum, and provides the sum (Sigma 4 to Sigma 1) and carry outputs (C4, C0).

What are the key pins to remember when wiring the adder (74 LS 83)?

Important pins include the input pins A4 to A1, B4 to B1, the carry input (C0) which must be grounded, and the sum and carry output pins (Sigma and C).

How do you test the BCD to 7-segment driver (74 LS 47)?

Connect the binary inputs (D, C, B, A) to the driver, and ensure the corresponding LEDs on the 7-segment display light up to form the correct digit. Test the display by changing the inputs.

What is the purpose of connecting a current-limiting resistor to the 7-segment display?

A current-limiting resistor (typically 300 ohms) is used to prevent excessive current from damaging the LEDs in the 7-segment display.

How do you ensure that the 7-segment display is functional before starting the experiment?

You can connect the lamp test bar (pin 3) to ground instead of VCC, which will make all LEDs on the display glow, confirming that the display is working.

What happens when the input to the comparator is changed from '1100' (12) to '0100' (4)?

When the input to the comparator is changed, the output displayed on the 7-segment display changes accordingly. For '1100' (12), the display shows 12, and for '0100' (4), it switches to 04.