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4.1 State the light-altering principle of operation of the liquid crystal display (LCD) - NSC Electrical Technology Digital - Question 4 - 2019 - Paper 1
Question 4
4.1 State the light-altering principle of operation of the liquid crystal display (LCD). 4.2 With reference to encoders and decoders, answer the questions that foll... show full transcript
Worked Solution & Example Answer:4.1 State the light-altering principle of operation of the liquid crystal display (LCD) - NSC Electrical Technology Digital - Question 4 - 2019 - Paper 1
Step 1
State the light-altering principle of operation of the liquid crystal display (LCD).
Answer
The light-altering principle of a Liquid Crystal Display (LCD) is based on the manipulation of light through liquid crystals. When an electric current passes through the liquid crystals, they align themselves in such a way that they can either block or allow light to pass through. This creates images by controlling the pixels, thus producing varying degrees of light and color on the display.
Step 2
Draw the circuit diagram of a simple two-digit-binary-input-to-four-digit-decimal-output decoder using TWO NOT gates and FOUR gates.
Answer
To draw the circuit diagram, start with two inputs labeled A and B. Use TWO NOT gates to invert these inputs. The outputs of the NOT gates will feed into FOUR AND gates, which will produce the decimal outputs 0 to 3 based on the combination of inputs A and B. Ensure all connections and gates are clearly labeled.
Step 3
Step 4
Step 5
Explain the function of the driver transistors found in the BCD-to-seven-segment display decoder.
Answer
The driver transistors in the BCD-to-seven-segment display decoder function as amplifiers and switch controls for each segment of the display. They ensure that the appropriate segments illuminate according to the binary input by providing necessary power to each segment, effectively converting logic levels into visible outputs.
Step 6
Complete the truth table of a BCD to seven-segment decoder connected to a seven-segment display in TABLE 4.3.3 on the ANSWER SHEET FOR QUESTION 4.3.3.
Answer
| B | C | D | A | a | b | c | d | e | f | g |
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 |
| 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 0 |
| 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 |
| 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 0 |
| 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 |
| 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 1 |
| 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 0 |
| 1 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 1 | 0 |
| 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 1 |
| 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 |
Step 7
Draw the logic circuit of this half adder using an AND gate and an XOR gate.
Answer
The logic circuit of a half adder consists of an XOR gate to produce the sum output (S) and an AND gate to produce the carry output (C). Inputs A and B are fed into the XOR gate for sum output, and into the AND gate for carry output.
Step 8
Step 9
Draw the logic circuit of this flip flop on the ANSWER SHEET FOR QUESTION 4.5.
Answer
The logic circuit for a clocked RS flip-flop involves two NAND gates. The SET input (S) goes to one NAND gate, and the CLEAR input (R) feeds into the other. The outputs connect to form the feedback loop, ensuring stable state retention.
Step 10
Step 11
Name TWO applications of counters.
Answer
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Frequency dividers: Counters are often used to divide the frequency of a signal, which can be useful in various electronic applications.
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Digital clocks: Counters are integral in tracking time in digital clocks by counting pulses from a clock source.
Step 12
Explain the operation of this four-stage asynchronous binary-to-BCD counter.
Answer
In a four-stage asynchronous binary-to-BCD counter, each flip-flop in the counter toggles on the leading edge of the clock pulse. This setup counts binary values and converts them to binary-coded decimal (BCD) when the maximum count of 9 is reached. At this point, special feedback logic resets the counter back to 0 or carries over to increment the next stage.