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Refer to the LED seven-segment display and answer the questions that follow - NSC Electrical Technology Electronics - Question 5 - 2023 - Paper 1
Question 5
Refer to the LED seven-segment display and answer the questions that follow. 5.1.1 Explain the difference between a common anode and a common cathode. 5.1.2 State ... show full transcript
Worked Solution & Example Answer:Refer to the LED seven-segment display and answer the questions that follow - NSC Electrical Technology Electronics - Question 5 - 2023 - Paper 1
Step 1
Explain the difference between a common anode and a common cathode.
Answer
A common anode seven-segment display has all the anodes of the LEDs connected together to a positive voltage supply. Each individual segment's cathode is connected to a control pin. When a segment needs to be illuminated, its corresponding control pin is grounded, allowing current to flow from the anode through the LED to the grounded pin.
In contrast, a common cathode display has all the cathodes of the LEDs connected together to ground. The anodes are connected to control pins. To light up a segment, the corresponding control pin is supplied with a positive voltage, allowing current to flow from the control pin through the LED to the common cathode, completing the circuit.
Step 2
State TWO methods that use transistors to connect the power supply to the seven-segment display.
Answer
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Transistor as a switch: A transistor can be used as a switch, where a low voltage signal applied to the base controls the larger current flowing from the collector to the emitter. This method allows segments to be turned on and off efficiently, controlling the display from a microcontroller.
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Darlington pair configuration: This configuration involves using two transistors to amplify current. This method can drive higher power loads, ensuring that the segments of the seven-segment display receive adequate current to illuminate brightly.