Digital sine wave generator
555, 74HC191, 74HC4028, 7476, 7400
Oscillateurs   /    Oscillators
Électronique / Electronic

In this project, you're going to make a sine wave using digital technology. Take a look at the schematic. The circuit consists of an oscillator, counter, decoder, and a resistor network. The resistance values in the resistor network are different from one another. Given these hints, try to guess how you can generate a sine wave digitally.

Anyway, finish wiring and turn power ON. You'll hear a monotone from the speaker.

U1 555 is an oscillator, and the counter U2 counts up with the pulses from U1.

The outputs QA - QC of the counter U2 are decoded by the decoder U4.

As the counter U2 counts up, the output Q9 of the decoder U4 changes to H, when the RS flip-flop U3 is reset to switch the counter U2 to count-down mode.

The count-down proceeds until the output Q0 of the decoder U4 goes H, when U3 is set and U2 switches back to count-up. In this way, the counter shifts back and forth in the range of values 0 - 9.

In the meantime, the outputs Q0 - Q9 of the decoder U4 change to H one after another. Therefore, the voltage divided by the resistors connected to Q0 -Q9 and by R13 come to have 10 different voltage values as shown in Figure 1, so that the oscillating tone of this waveform is emitted from the speaker.

 Bill Of Materials For Digital sine wave generator 14 Resistors Quantity: References Value 1 R1 69k 1 R2 27k 1 R3 1M5 1 R4 330k 2 R5, R12 100k 1 R6 33k 1 R7 12k 1 R8 6K8 1 R9 3K3 1 R10 1k 1 R11 270R 2 R13, R14 10k 4 Capacitors Quantity: References Value 3 C1, C3, C4 0.01uF 1 C2 0.001uF 5 Integrated Circuits Quantity: References Value 1 U1 555 1 U2 74HC191 1 U3 7476 1 U4 74HC4028 1 U5 74HC00 4 Transistors Quantity: References Value 3 Q1-Q3 2SC945 1 Q4 2N5401 8 Diodes Quantity: References Value 8 D1-D8 1N4148 3 Miscellaneous Quantity: References Value 1 BAT1 6V 1 LS1 SPEAKER 1 ON OFF

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