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Simple Beeper Circuit

How to build a simple beeper circuit is described in this article.

An asymmetric multivibrator is a type of electrical circuit that produces sound when a button is pressed.

A little speaker produces the sound.

Learning about music and electronics through this project is fun.

What is a Beeper Circuit:

The Beeper circuit is a simple yet advanced electrical device that constantly beeps making it perfect to use as an alert or indicator in places like hospitals, police stations or fire stations.

Circuit Working:

Parts List:

CategoryDescriptionQuantity
Resistors1.5k CFR 1/4 W1
4.7k CFR 1/4 W1
CapacitorCeramic 470nF1
SemiconductorTransistor BC5471
Transistor 2N29071
Speaker 8Ω1
Battery 3V1
Push button switch1

The beeper circuit mentioned above functions as an asymmetric multivibrator producing audible signals by means of a feedback loop using two transistors (NPN and PNP).

A pushbutton initiates the circuit and a resistor allows you to change the audio frequency.

Here is a description of how the circuits work:

Setting up:

Starting Point (Stable Point):

Pressing the pushbutton:

Change to an Unstable Situation:

Capacitor Charging:

Transition Back to Stable State:

Capacitor Discharging:

The cycle is repeated:

Audio frequency that can be adjusted:

Using Earphones Optionally:

Formulas and Calculations:

Following are the formulas with calculations for Simple Beeper Circuit:

One can develop a basic astable multivibrator circuit to make a beeper circuit.

When the push button switch is pressed this circuit creates a square wave signal to drive the speaker and release a beeping sound.

Calculating Frequency:

For a simple astable multivibrator the oscillations frequency f is roughly calculated as follows:

f = 1.44​ / (R1+2 * R2) * C

where,

Enter your inputs and use this formula to calculate the frequency of the beeping noises.

In our diagram: R1 = 1.5k, R2 = 4.7k and C = 470nF

So the frequency will be approximately:

f = 1.44​ / (1.5k + 2 * 4.7k) * 470 ×10−9

1.44​ / (1.5 + 9.4) * 470 × 10−6 =

1.44​ / 11.4 * 470 × 10−6 = 1.44​ / 5.358 × 10−3 = 268 Hz

This gives an approximate value of the frequency which may differ significantly based on the actual values and tolerances of the components.

How to Build:

To build a Simple Beeper Circuit follow the following steps for connection of the circuit:

Identify Components:

Assemble all necessary parts and confirm that they work with the circuits requirements.

Positioning of Transistors:

Connect Speaker :

Resistor R1 Connection:

Installing a Pushbutton:

Connecting the battery:

Conclusion:

By carefully assembling these components one can create a flexible beeper circuit that provides an interesting and adaptable audio output experience with an adjustable audio frequency range.

The circuit generates audible signals using the concepts of an asymmetric multivibrator and the addition of a pushbutton and resistor R1 provides the audio tone with more usefulness and flexibility.

References:

Buzzer or Beeper

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