Using electrical components, a simple two-way intercom circuit enables communication between two places.
Imagine a primitive office or home communication system.
In this circuit the below mentioned components play the main role:
Microphone: Transforms your speech into an electrical signal.
Audio amplifier: Increases the poor microphone signals strength to the point where it can power a speaker because of IC LM386 a common chip used.
Speaker: Transforms the electrical signal that has been amplified back into a sound that can be heard.
SPDT switch: This switch lets you choose between the ‘talk’ and ‘listen’ modes.
Battery: Gives power to the circuit.
Circuit Working:
Parts List:
| Category | Item | Quantity | Power Rating |
|---|---|---|---|
| Resistors | 10Ω | 1 | 1/4 watt |
| 4.7k | 1 | 1/4 watt | |
| 10k | 1 | 1/4 watt | |
| Potentiometer | 10k | 1 | – |
| Capacitors | Ceramic 0.1μF | 1 | – |
| Ceramic 0.047μF | 1 | – | |
| Electrolytic 10μF 25V | 2 | – | |
| Electrolytic 1000μF 25V | 1 | – | |
| Semiconductors | IC LM386 | 1 | – |
| SPDT switch | 1 | – | |
| Electret Microphone | 2 | – | |
| Components | 8Ω speakers | 2 | – |
The breadboard, a useful tool for experimenting with electrical parts is used to build the circuit.
The LM386 audio amplifier chip is essential for this operation.
This chip greatly increases the strength of a weak electrical signal, such as your voice coming from the microphone.
The LM386s gain controls how much the signal is amplified.
It has a default strength of 20 times and a maximum strength of 200 times.
In this instance, the maximum gain of 200 is obtained by applying a capacitor across particular pins 1 and 8.
The speakers volume is controlled by a resistor R2.
A 4.7k resistor is used to regulate the loudness in this instance.
To determine your ideal volume, try with various resistor values between 1k and 100k.
The IC LM386 pin 5 amplified signal is sent to both speakers, one at each position.
An SPDT switch is employed since the circuit is unable to enhance sound from both microphones at the same time.
One microphone can only be connected to the amplifier at a time thanks to this switch, which functions as a gatekeeper.
This guarantees that, like a walkie talkie, only one person may speak at a time.
We refer to this kind of communication as half duplex.
You may choose which microphone is on and who can talk by flicking the switch.
Formulas:
The circuit schematic above, which may be used to create a basic two-way intercom circuit using the IC LM386 it includes pertinent calculations and explanations:
Calculating Amplifier Gain for LM386:
The value of the bypass capacitor C1 connected between pins 1 and 8 of the LM386 determines the gain Av of the amplifier.
The gain formula is: Av = 1+Rf / Rin
where,
- The resistance between pins 1 and 5 is denoted by Rf, which is the potentiometer.
- The resistance between pin 3 and ground is denoted by Rin.
To determine the appropriate gain, adjust Rf and Rin.
For instance, the gain would be if Rf = 10k and Rin = 10k
Av = 1+10k / 10k = 2
Your intercom applications particular requirements, such as the required gain, frequency responsiveness, and power supply voltage, should be taken into consideration while selecting the precise values for the resistors, capacitors, and potentiometer.
To help you with your design, consult the application notes and datasheets for the LM386 and other components.
How To Build:
To build a Simple Two-Way Intercom Circuit following the below mentioned steps for circuit connections:
- Gather all the components mentioned in the circuit diagram above.
- Connect pin 1 to pin 8 of IC1 LM386 through capacitor C1.
- Connect pin 2 and pin 4 of IC1 LM386 to ground.
- Connect pin 3 of IC1 LM386 to one leg of 10k pot.
- Connect pin 5 of IC1 LM386 to one end of speaker 2
- Connect pin 6 of IC1 LM386 to +5V positive supply.
- Connect pin 7 of IC1 LM386 to capacitor C3 and ground.
- Connect capacitor C4 and resistor R1 in series between pin 5 of IC1 LM386 and ground.
- Connect VR1 pot 1 leg to center pin of SPDT switch through capacitor C2 and resistor R2, second leg of pot to pin 3 of IC1 LM386 and 3rd leg of pot to ground.
- Connect 1st leg of SPDT switch to positive side of MIC2 and 3rd leg of SPDT switch to positive side of MIC1, connect negative ends of both the MICs to ground.
- Connect speaker1 and speaker2 one end of both the speakers to ground and other end of both the speakers to pin 5 of IC LM386
Safety Measures:
- Make sure the battery or power supply you are using has the correct voltage and amperage rating.
- Make sure it complies with the specifications of the circuits parts.
- A circuit should never be powered by a source that is higher than its voltage rating.
- Batteries should always be handled carefully, and they should be disposed of appropriately in accordance with local laws.
- By taking these precautions, you may reduce the possibility of electrical risks and guarantee a fun and safe building process for your intercom circuit.
Conclusion:
A simple two-way intercom circuit provides a minimal communication system.
It boosts microphone signals using an IC LM386 audio amplifier to enable communication between two sites.
Although the circuit is rather simple, using an SPDT switch guarantees that only one person may speak at a time.
Building electrical circuits and comprehending fundamental ideas like signal regulation and amplification are made easy with this project.
Always emphasize safety when using electronics by taking the necessary safety precautions.
References:
A Cost-Effective Two-Way Household Wireless Door Intercom System