This circuit describes about a special kind of electronic volume control that uses electronic parts rather than a knob.
This kind of circuit uses small computer chips to regulate the loudness whereas regular volume knobs use resistors.
This can provide more features and become more accurate.
Circuit Working:
Parts List:
| Category | Quantity |
|---|---|
| Resistors (All resistors are 1/4 watt) | |
| R1, R2, R20, R32 22k | 4 |
| R3 18k, R4 15k, R5 10k, R6 8.2k, R7 5.6k, R8 4.7k, R9 1k, R10 300Ω | 1 each |
| R11 1Ω, R12 300Ω, R13 1k, R14 15k, R16 8.2k, R17 10k, R18 15k, R19 18k | 1 each |
| R21 47k | 1 |
| R22 to R31, R33 to R43 10k | 21 |
| Preset VR1 47k | 1 |
| Capacitors | |
| C2 Ceramic 0.1μF | 1 |
| C1 Electrolytic 10μF 25V | 1 |
| C3 to C12 Electrolytic 1μF 25V | 10 |
| Semiconductors | |
| Red LED1 to LED10 5mm 20mA | 10 |
| Transistors T1 to T10 BC547 | 10 |
| IC1 555 and IC2 4017 | 1 each |
| S1 Push-to-on switch | 1 |
| S2 1 pole 2-way switch | 1 |
A decade counter IC2 4017 and many transistors work together to provide this circuits function.
Transistors receive input at their collectors and generate their output from their emitters.
The IC2 4017 output controls when the matching transistor reaches maximum.
To get the signal to the amplifier the emitter output passes through a coupling capacitor which removes DC components.
The equivalent transistor T2 overflows when pin 4 of IC2 4017 goes high allowing the input signal to be sent directly to the output through the collector resistance.
Press switch S1 to begin the operation.
Pulses are produced at regular intervals by the timer IC1 555 and sent into IC2.
The output of IC2 4017 regulates the choice of transistor.
Release the switch once the volume is at the right level.
S2 is placed at A to reset the counter switch.
The following below formula is used to modify the output pulses time period.
Formula:
The time constant Td of a circuit which is most likely used in a timer circuit are explained by the below formulas:
Td = 0.693(R1 + 2√R1 + 2R3²) C1 seconds
here,
- The circuits time constant or Td is measured in seconds.
- The constant value of 0.693 is calculated using the mathematical features of capacitor charging over time.
- The resistance of resistor R1 is indicated as R1 in ohms.
- The square root of resistor R1 is represented as √R1.
- Resistor R3 multiplied by itself twice or twice the square of its resistance is equal to 2R3².
- The capacitance of capacitor C1 is indicated as C1 in farads.
How the formula works:
Basically the formula calculates the charging time of the circuits capacitor C1.
Resistors R1 and R3 affect the charging speed.
This is just a short description.
R1 or R3 Greater Resistance:
The capacitor takes longer to charge when the resistance is larger which raises the time constant Td.
Increased C1 Capacitance:
Because it takes longer to reach its maximum voltage and can keep more charge a bigger capacitor has a larger time constant.
How to Build:
To build a Simple Digital Volume Controller Circuit follow the blow steps:
Schematic Design:
- By using the information given in the article create a schematic diagram mentioned above.
- Design a PCB layout or arrange components on a breadboard.
Connect ICs:
- Connect the IC 4017 and IC 555 to the proper Vcc and GND power supplies.
- Connect IC 4017s pin 4 to the transistor base or any other suitable input.
Connections for Transistors:
- Depending on their functions in the switching process connect transistors T1 and T2 to the circuit.
Positioning of the Resistor:
- R1, R2 and R3 resistors should be connected to the circuit in order with their specified values.
Connections for Capacitors:
- To block DC components and guarantee correct signal transmission connect capacitors C1 and coupling capacitor.
Wiring a switch:
- To control the circuits working connect switches S1 and S2 with S1 starting the process and S2 resetting the counter.
Amplification and Preamplifier:
- Make the proper connections between the amplifier input and preamplifier output.
Source of Power:
- Give the circuit the required power supply voltage Vcc.
- Check the connections very carefully.
- Turn the circuit on and check that it works.
- Use an oscilloscope or other measurement instruments to ensure the desired actions.
Modifications:
- If required adjust the circuit to get the right volume control and switching actions.
Caution:
To avoid errors it is important to check the datasheets of the particular components that are using and verify the connections twice.
If electronics are unfamiliar think about consulting with experts in this field or ask someone with experience for help.
Conclusion:
The main benefits of Simple Digital Volume Controller Circuit include accurate control, remote operation and connectivity with digital audio processing systems.
They are frequently found in home theater systems, multimedia speakers, audio amplifiers and other audio equipment that requires automation and digital control.