The IC 555 chip is quite helpful in a lot of electronic circuits.
This project differs slightly from the usual usage in timing circuits.
We will build a microphone amplifier in this project using the IC 555.
Initially the voice is captured by a microphone.
It then gets a modest boost via a transistor which is like a tiny switch.
Finally to increase the volume even further the IC 555 chip provides an additional push.
What is a IC 555 Amplifier Circuit:
Although we can use it like a pulse width modulation circuit or a timer oscillator the IC 555 is not commonly used as an independent amplifier.
Timer and pulse generation applications is where the IC 555 is most frequently used.
For setting up the IC 555 as a voltage comparator and design a simple amplifier circuit but however, external components can be used.
This method is less popular and does not use the 555 IC for its main function.
Circuit Working:
With the 555 amplifier circuit mentioned above one can modify the design as shown in the circuit diagram below if anyone wishes to use an external music signal:
Parts List:
| Category | Component | Quantity |
|---|---|---|
| Resistors | 10k CFR | 1 |
| 330Ω CFR | 1 | |
| 1k CFR | 1 | |
| 680k CFR | 1 | |
| 100k CFR | 1 | |
| 47k CFR | 1 | |
| Capacitors | 0.1μF | 1 |
| 10μF | 2 | |
| 1nF | 1 | |
| Semiconductors | Transistor BC547 | 1 |
| IC 555 | 1 | |
| Electret Microphone | 1 | |
| Speaker 8Ω | 1 |
The 555 IC requires a particular setup in order to be used as an amplifier.
In this project the internal transistor is used to remove the discharge function by setting up the integrated circuit in astable mode without a discharge pin.
The control voltage pin then receives the sources pre-amplified audio signal.
The 555 ICs internal reference voltages is changed by connecting an external voltage to the control voltage pin.
This external voltage immediately affects the 555s IC timing and modifies the output pulse width by exceeding the internal voltage divider network.
The 555 IC circuits timing functions is accurately controlled by supplying an external voltage to the CV pin which accordingly changes the threshold and trigger levels.
When there is no audio input than pin 5 receives no voltage which causes the IC 555 to generate pulse frequencies higher than 60 kHz that cannot be detected via a loudspeaker.
The output pulse width fluctuates when an audio signal is supplied because pin 5 gets electricity.
The loudspeaker may produce this modulated pulse width signal as sound.
It is important to understand how the electret mics work in this setup.
A capacitor is made up of a diaphragm and a conductive backplate with a tiny air gap that works as an insulator.
The capacitance between the diaphragm and the backplate fluctuates as sound waves strike it.
The sound wave gets converted into an electric audio signal by this process.
The output audio signals low amplitude requires pre-amplification using a transistor BC547.
Formulas:
The following formulas are applied to the astable multivibrator setup which is frequently used for oscillation:
f = 1.44 / [(R1 + 2 * R2) *C]
where:
- f is the frequency of the output square wave in hertz Hz
- R1 and R2 are resistors in ohms Ω connected as shown in the specific circuit diagram
- C is the capacitor in farads F connected as shown in the specific circuit diagram
Pulse High Time (thigh):
thigh = 0.693 * R1 * C
where:
- thigh is the duration of the high portion of the output square wave in seconds (s)
Note:
These formulas offer a place to start when creating a simple oscillator circuit with a IC 555.
How To build:
To build a Simple IC 555 Amplifier Circuit follow the following steps for connection:
- Place the 555 IC on the PCB.
- Connect pin 8 to the positive supply of the PCB.
- Connect pin 1 to the ground supply of the PCB.
- Connect pin 6 to pin 2 using a resistor R1.
- Connect pin 6 to pin 7.
- Connect a capacitor C1 between pin 6 and the ground supply.
- Connect the positive terminal of the condenser microphone to the collector of transistor BC547.
- Connect the emitter of transistor BC547 to the ground supply.
- Connect the base of transistor BC547 through a resistor R2 to the positive supply.
- Connect the junction of the resistor R2 and the base of transistor BC547 to the output of the condenser microphone.
- Connect pin 3 of the 555 IC to the positive terminal of the loudspeaker.
- Connect the negative terminal of the loudspeaker to the ground supply.
- Connect pin 8 of the 555 IC to the positive supply.
- Connect pin 1 of the 555 IC to the ground supply.
- Apply power to the circuit through the power supply.
- Speak into the condenser microphone and observe the sound reproduction through the loudspeaker.
Conclusion:
To conclude this new design of using the 555 IC as an amplifier provides a fascinating idea for modifying and enhancing audio signals.
With the help of the construction guidelines fans are able to understand the experiment and explore the circuit designs which are possibly uses in a variety of audio related tasks.