Comfortable and quiet, without introducing electrical noise in the assembly, compared to an analog potentiometer, the digital potentiometer presented is made with general purpose integrated circuits (non-specialized). Do you want to have a volume controller with electronic control (up and down) in 16 steps? Then we recommend you to make this installation!
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How does the electronic scheme work?
The main elements are the two electronic switches of the type 4066 (for the two channels). Their order is made in BCD code (Decimal Coded Binary) by the binary counter (reversible), CD mode 40193.
Its command is made on the two inputs: for direct counting, on pin 5, and for reverse counting (descending) on pin 4. The effective command is made with the help of the two push-buttons, marked with S1-UP and S2-DOWN.
If you want to go directly to the minimum position, then press the S3-RESET button. So RESET command, implies the maximum attenuation of the signal.
The volume adjustment is done by the combined connection of four resistors (R6-R9 for the left channel and R9-R12 for the right channel) which achieves a relatively linear increment or decrement in 16 steps of the output signal, compared to the input one. .
The clock generator is made with the integrated circuit LM555. It provides the signal corresponding to the speed of incrementing (decrementing) the volume. The assembly does not require any adjustment, if it is done correctly. The power supply must be very well filtered because audio signals are switched.
Printed circuit board design
Design suggestive for use
List of required components
R1, R2, R4 = 10k;
R3 = 150k;
R5, R9 = 1k;
R6, R10 = 2.2k;
R7, R11, R13, R14 = 4.7k;
R8, R12 = 8.2k;
R15 = 330k;
C1 = 10uF;
C2 = 1uF;
C3 = 100nF;
SW1, SW2, SW3 = push buttons;
1 x LM555;
1 x CD40193 (CMOS predictable up / down counters);
2 x CD4066 (CMOS Quad Bilateral Switch);
5 x terminal contacts (for stereo audio input, stereo audio output and power);