This Tutorial demonstrates the simple and useful security alarm based on Infrared radiation using 555 Timer IC. The circuit uses an Infrared (IR) sensor. Infrared radiation is continuously falling on a photodiode. Whenever the infrared radiations break down by any means an alarm is triggered through the speaker.
The circuit has two stages. The first one is an IR emitter and an IR receiver stage while the second one is an Astable multivibrator timer circuit. An IR stage operates the reset pin of the timer circuit. As the IR rays are blocked the multivibrator timer circuit oscillates.
Hardware Components
The following components are required to make IR Security Alarm Circuit
| S. No | Components | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Battery | 9v | 1 |
| 3. | IR LED Pair | – | 1 |
| 4. | IC | NE555 Timer | 1 |
| 5. | Op-Amp IC | LM358 | 1 |
| 6. | Variable Resistor | 10k ohm | 1 |
| 7. | Resistors | 100 ohm, 220 ohms, 10k, 100k | 1, 1, 1, 1 |
| 8. | Capacitor | 10uF | 1 |
| 9. | Buzzer | – | 1 |
555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
LM358 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM358
IR Security Alarm Circuit
Working Explanation
An IR sensor consists of an IR led and a photodiode. An IR-led ejects IR radiation whereas the photodiode these radiations. The photodiode conducts the current in a reverse direction. The output of the photodiode changes when the light falls on it.
This change in voltage is observed by the voltage comparator which produces an output according to this voltage change. An IR led gives an IR ray so it should be in a straight line with the photodiode. The rays will then directly fall on the photodiode. Whenever someone comes in between the radiations these rays stop falling on the photodiode. This will help the buzzer to start beeping. The Timer IC stops the buzzer after some time.
Application
- An IR-based security alarm circuit has plenty of advantages in homes, shops, and banks.
- This circuit is useful in any kind of restricted area as it detects any slight movement and activates an alarm.
