This article tell how to make new type of Infrared (IR) Intruder Alarm Circuit, where it can find person who walk through invisible light beam.
Circuit have two main part: one transmitter and other one is receiver.
Transmitter send out one infrared light beam across a room and if someone goes in front of light the LED blink and alarm makes sound.
And receiver detects IR light and gives signal when beam breaks, so alarm turns ON.
Also, this project is good for learning more about electronics.
What is a Infrared IR Intruder Alarm Circuit:
One type of security device used in infrared technology is to find intruder is Infrared IR Intruder Alarm Circuit.
When warm body or person make through then infrared light sensor we can see it, also main idea is to use IR transmitter and receiver to make one barrier or zone.
Furthermore, when intruder walk through this area they break the IR beam and alarm starts making sound.
Transmitter Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors | 470Ω 1/4 W CFR | 2 |
| 2.2k 1/4 W CFR | 1 | |
| Preset 10k | 1 | |
| Capacitors | Ceramic 47nF | 1 |
| Electrolytic 10µF 25V | 1 | |
| Semiconductors | IC 555 | 1 |
| IR Emitter LED | 1 |
Firstly, this transmitter circuit uses IC 555 timer work like astable multivibrator which we can see in above diagram.
Infrared LED1 make light blink at around 5KHz speed and some good things of this blinking system are:
- Blinking frequency is 5KHz
- Its pulse help to know IR light from other normal lights
- AC coupling help to handle light change in the room
- Battery transmitter also needs to save power
Adjust frequency of transmission depend on transmitter and receiver both.
Formula:
Below formula is to find frequency of 555 astable circuit using parts value:
Frequency (f) = 1.44 / (R1 + RV1 + 2R2) × C1
where:
- f is frequency in hertz Hz
- R1 is resistor R1 value in ohms Ω
- RV1 preset value in ohms Ω
- R2 is resistor R2 value in ohms Ω
- C1 is capacitor C1 value in Farads F
Receiver Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 W CFR) | 47k | 3 |
| 100k | 3 | |
| 100Ω | 1 | |
| 5.6k | 1 | |
| Capacitors | Ceramic 10nF | 1 |
| Ceramic 100nF | 1 | |
| Electrolytic 2.2µF 25V | 2 | |
| Electrolytic 100µF 25V | 1 | |
| Semiconductors | Transistor BC547 | 1 |
| Diodes 1N4148 | 3 | |
| IC 741 | 1 | |
| IR Receiver LED | 1 | |
| Relay 12V | 1 |
We use one infrared receiver diode LED1 in the receiver circuit and we reverse bias it, as shown in the above circuit diagram.
When IR light comes diode resistance goes up and voltage drop happen at point between R1 and LED1.
Here are main parts in receiver circuit:
Op-Amp Setup:
R2 and R3 provide input at half of the power supply and R4, R5 and C2 help set the amplifier gain.
At 5KHz gain becomes very high which is even thousand times and when receiver gets signal Op-Amp IC1 give AC output signal around 5KHz.
Other circuit parts:
D1, D2, and C4 act as a voltage doubler and the relay and Q1 transistor handle the switching.
When C4 get enough charge the relay turn ON and if signal stops or break then relay turns OFF.
How to Build:
Below are the steps to build the Infrared (IR) Intruder Alarm circuit:
Transmitter Circuit:
- First, connect all parts same like in circuit diagram.
- Next, we set IC 555 as an astable multivibrator.
- After that, connect LED1 infrared emitter to IC 555 output pin.
- Now to get around 5KHz frequency change the value of resistor R and capacitor C.
- Also, use good power source or battery to give power to circuit.
Receiver Circuit:
- Join all parts same like in receiver diagram.
- Then make LED1 IR receiver in reverse bias using resistor R1.
- Also, set IC1 Op-Amp as non-inverting AC amplifier.
- After that, use resistors R2 and R3 to make input half of power supply.
- And also, use R4, R5 and C2 to calculate amplifier gain.
- Set gain high at 5KHz frequency.
- Use diode D1 and D2 to double the voltage.
- Also use capacitor C4 charges and turn ON transistor Q1 and relay.
- Then put diode D3 to protect from back current EMF.
- After that capacitor C3 and C5 help to stop power noise from relay.
- Join relay to alarm or any warning system and be sure power supply is good and stable.
Alignment and Testing:
- Also, place transmitter and receiver in straight line so IR light goes directly to receiver and turn ON the power.
Test it:
- If we block the IR light then relay should turn ON and alarm makes sound.
- So use preset potentiometer to adjust transmitter frequency for better working.
Note:
- Also, we can try changing and testing, depending on what we want or what is our room condition.
Conclusion:
Overall, this smart and Infrared (IR) Intruder Alarm Circuit gives more safety because of good alignment, fast working and strong receiver parts.
Moreover, we can change frequency and test with different place of transmitter and receiver to make it work better for our design.