DIGITAL_VOLUME_CONTROL

Published:2009/7/12 20:37:00 Author:May | From:SeekIC

The heart of the digitally operated volume control is IC2, a 4067 16-channel analog multiplexer. Depending on the logic state on pins A, B, C, and D of the multiplexer, one of its 16 inputs or outputs is connected to pin 1, which is the wiper of the control. Because a 1-kΩ resistor has been connected between each input and output, the multiplexer can be considered a linear potentiometer with 16 fixed steps. Its overall resistance is 15 kΩ. It is, of course, possible to use a different value for each of the resistors to obtain a different characteristic. The setting of the potentiometer is controlled by counter IC1. Dependent on the position of switch S1, the counter moves one step up or down when switch S1 is changed over. Circuits IC3A and IC3B debounce S2.A jump from 0000 to 1111 or the other way around is not possible, because further count pulses are suppressed with the aid of the CO line. This line is logic low when both the counter state and signal U/D are 0.When U/D is high and the counter state is 15, COagain becomes logic low. It is then necessary to reverse the logic state at U/D, and thus the direction of counting. The volume control draws a current of around 1 mA.



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