Simple IC 555 Timer Based Vibration Alarm Circuit

The IC 555 timer based vibration alarm circuit is a cool and easy electronic setup that can sense vibrations and make noise and light to alert you.

These circuits are commonly found in security systems, monitoring machines in factories, and anti theft gadgets.

The main part of this circuit is the handy IC 555 timer which is set up in a way that it gives a steady signal when it detects vibrations using a sensor.

Circuit Working:

Parts List:

The above circuit diagram features an IC 555 set up in monostable mode.

A vibration sensor is linked to the trigger pin 2 of the IC 555 using a resistor R3 and a capacitor C2 to help reduce noise.

Pin 5, which is the control voltage, is connected to the ground through a capacitor C1 to keep the IC stable.

The output pin 3 connects to the base of a BC547 transistor via a current limiting resistor R2.

The transistors collector powers the buzzer and LED.

When there are no vibrations the vibration sensor does not activate, and the output from the IC 555 pin 3 remains low.

When the vibration sensor picks up mechanical vibrations it sends a small electrical signal to trigger pin 2 of the IC 555.

This makes the IC produce a high pulse for a time based on the values of R3 and C2.

The high output from the IC 555 turns on the BC547 transistor allowing current to flow through the buzzer and LED creating both sound and light alarms.

The ON/OFF switch in the circuit is super important because it controls the power going to everything.

When you flip the switch to ON, the battery sends power to all the parts and the circuit starts working.

But when you switch it OFF, it cuts off the power which helps save the battery and turns off the system when you do not need it.

After the vibrations stop and the timer runs out the output from pin 3 goes back to low which turns off the buzzer and LED.

Formulas and Calculations:

Below are the formulas with calculations for Simple IC 555 Timer Based Vibration Alarm Circuit:

Pulse Duration Formula for IC 555 in Monostable Mode:

T = 1.1 × R3 × C2

where,

• T is the output pulse duration in seconds
• R3 is the timing resistor in ohms
• C2 is the timing capacitor in farad

Example Calculation:
Suppose R3 = 1MΩ (1,000,000 ohms) and C2 = 100µF (0.0001 farads):
T = 1.1 × 1,000,000 × 0.0001
T = 110 seconds

Base Current of Transistor (BC547):

Ib = (Vout – Vbe) / R2

where,

• Ib is the base current of the transistor in amperes
• Vout is the output voltage from IC 555 around 9V for a 9V battery
• Vbe is the base emitter voltage of the transistor around 0.7V
• R2 is the resistor connected to the base in ohms

Example Calculation:
If Vout = 9V, Vbe = 0.7V, and R2 = 100Ω:
Ib = (9 – 0.7) / 100
Ib = 0.083 A or 83mA

LED Current Limiting Resistor:

R = (Vbattery – Vled) / Iled

where,

• R is the resistor value in ohms
• Vbattery is the supply voltage 9V
• Vled is the forward voltage of the LED around 2V
• Iled is the current through the LED around 20mA or 0.02A

Example Calculation:
If Vbattery = 9V, Vled = 2V, and Iled = 0.02A:
R = (9 – 2) / 0.02
R = 350Ω

Use the closest standard resistor value, such as 330Ω or 360Ω.

How to Build:

To build a Simple IC 555 Timer Based Vibration Alarm Circuit follow the below mentioned steps:

• Gather all the necessary components as mentioned in the above circuit diagram.
• Connect pin 1 of IC1 555 to GND.
• Connect pin 2 of IC1 555 between the junction of R4 resistor from positive supply to vibration sensor to GND in series.
• Connect pin 3 of IC1 555 to base of transistor Q1 through resistor R2.
• Connect pin 4 and pin 8 of IC1 555 to positive supply.
• Connect pin 5 of IC1 555 to GND through capacitor C1.
• Connect pin 6 to pin 7 of IC1 555 through positive supply of resistor R3 and anode of capacitor C2 and cathode of C2 to GND.
• Connect collector of transistor Q1 to positive supply through a buzzer, and connect the emitter of Q1 transistor to GND.
• Connect a LED1 and a resistor R1 in series to positive supply between collector of transistor Q1 and buzzer.
• Connect a ON and OFF switch through positive supply through positive supply of 9V battery and negative supply of 9V battery to GND.

Conclusion:

The vibration alarm circuit that uses the IC 555 is a simple and effective method for sensing vibrations and giving both sound and light warnings.

You can use it in many places, like security systems or keeping an eye on machines in factories.

This circuit does not need a lot of parts, making it affordable, easy to build and very dependable.

It is a great tool for any situation where you need to keep track of vibrations and get alerts.