Hello viewers, in this tutorial we will learn about how to make visible intruder alarm.
VISIBLE INTRUDER ALARM is nothing but a simple visible light based security system which alarms and lets you know whenever the field created by the visible light is being intruded by any external source (may be thief).
- LED (ANY COLOR BUT PREFER RED LASER)
- 100K Resistor
- 470Ω Resistor
- BC547 Transistor
- 9 Volt Battery
- Battery Clip
- Bread Board
LED stands for Light Emitting Diode. It is a normal p-n junction diode which emits light whenever a current is passed through it. It is available in market in many different colors and of different power ratings.
LDR (LIGHT DEPENDENT RESISTOR)
LDR stands for Light Dependent Resistor. It is also called as a variable resistor whose resistance changes with respect to intensity of light falling on its surface. In other words the amplitude of current varies flowing through the LDR by varying the intensity of light falling on it because resistance of the LDR is inversely proportional to the intensity of light falling on it. Whenever the intensity of light increases then the resistance of the LDR becomes zero or say it comes to its rated resistance such as 10 Ω, 100 Ω, 1000 Ω etc. and behaves likes a conductor and whenever the intensity of the light decreases then the resistance of the LDR increases rapidly and reaches up to infinity normally 2000M Ω. And hence act as an insulator and flow of current becomes zero and amplitude of the current also becomes zero. It has two legs and there is no particular nomenclature of it legs, so there is no polarity of it.
Transistor is a semiconductor device which is basically of two types NPN and PNP. In PNP transistor, N-type semiconductor is sandwiched between two P-type semiconductors and in NPN transistor, P-type semiconductor is sandwiched between two N-type semiconductors. Transistors have three legs namely COLLECTOR, BASE and EMITTER. Here in this circuit we are using a BC547 transistor which is a very commonly used NPN transistor. You can use any type of NPN transistor such as BC548, BC549 etc. Its operation is very simple, whenever a current is applied in its base then the barrier between the collector and the emitter gets decreased and charge starts flowing from collector to emitter as both terminals gets shorted internally.
Resistor is an electronic device which opposes the flow of current through it. It has two terminals and there is no polarity so it can be operated in both forward and reverse direction. Its value is characterized by its color of 4 bands present on it. Value of resistance is calculated by color coding. Here in our case we are using a 100k and 470Ω resistor.
Battery is a voltage source device which stores charge and energy. There are many different types of batteries of different-different types of voltage ratings which are available in the market such as 1.5V, 3.7V, 4V, 6V, 9V, 11.7V, 12V etc. There are different types of batteries such as Lead-Acid battery, Lithium-Ion battery, Li-Po battery etc. Here in our case we are using a 9V battery.
Battery Clip is used to connect the battery from the circuit to the Bread Board. It has two wires in which Red one is +ve and Black one is –ve.
Bread Board is nothing but a trainer board which provides convenience to the hobbyists. In bread board you can build up any circuit without any soldering. The thing you need is just to plug and play. It has dotted bread like pores in it in which you can insert the legs of your any electronic components such as resistor, transistor, diode etc for the operation.
MECHANISM AND WORKING
Its working is very easy and simple and it is composed of very few basic electronics elements such as LDR (Photo Diode), LED, Resistor, Transistor, Battery etc. As we can see in this circuit there is two parts one part is transmitter part and other part is receiver part. The function of transmitter part is to transmit visible signals in the form of visible light and the function of receiver part is to receive the transmitted signal through LDR. But here the main role is played by the circuit section of the receiver part i.e. by the inverting process of transistor. Here the LDR is behaving like a switch because when the Light ray falls on the receiver part i.e. on the LDR then it detects the signal and completes the circuit and circuit gets shot circuited as the current coming from the 100k resistor directly goes to the ground through the LDR (as the LDR is now behaving like a conductor) rather going to the base of the transistor so the transistor remains in the off condition and buzzer also remains in the off state as the transistors is not providing any current to the buzzer (i.e. Ground through the emitter). But whenever the light is being interrupted or intruded by anyone or anything then the LDR doesn’t conduct any current through it (as in this case LDR is behaving like an insulator and its resistance becomes very high) so the current coming from the 100k resistor directly goes towards the base of the transistor rather going to the LDR and activates the transistor and after that transistor starts supplying the ground to the buzzer and alarm goes on and LED turns ON which indicates that there is some interruption between the path (i.e. robbery)
Note: – If you want to increase the range of the security system then use RED OR GREEN LASER instead of a normal LED.
CIRCUIT DIAGRAM OF VISIBLE INTRUDER ALARM SYSTEM
TRANSMITTER PART OF VISIBLE INTRUDER ALARM SYSTEM
RECEIVER PART OF VISIBLE INTRUDER ALARM SYSTEM
WIRING AND CONNECTION OF VISIBLE INTRUDER ALARM SYSTEM
STEP 1 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect battery clip to the Bread Board.
STEP 2 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect transistor to the breadboard
STEP 3 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect one leg of the 100k Resistor to the +ve and another leg to the base of the transistor.
STEP 4 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect Collector of the transistor to the –ve leg of the Buzzer and connect +ve leg of the buzzer to the +ve supply.
STEP (5A) OF VISIBLE INTRUDER ALARM SYSTEM:
Connect –ve leg of LED to the collector of the transistor and +ve leg of the LED to the 470R (ohm) resistor and connect another leg of resistor to +ve supply.
STEP (5B) OF VISIBLE INTRUDER ALARM SYSTEM
STEP 6 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect one leg of LDR (Photo Diode) to the ground and another leg to the Base of the transistor.
STEP 7 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect emitter of the transistor to the –ve (Ground).
TRANSMITTER PART OF VISIBLE INTRUDER ALARM SYSTEM
STEP 8 OF VISIBLE INTRUDER ALARM SYSTEM:
Connect one leg of 470R (ohm) resistor to the +ve supply and another leg to the LED’s longer leg i.e. anode (+ve) and also connect the shorter leg (-ve) of the LED to the Ground.
STEP 9 OF VISIBLE INTRUDER ALARM SYSTEM:
Make sure that you have maintained proper gap between the transmitter part and the receiver part and then connect the Battery to the Battery Clip.
STEP 10 OF VISIBLE INTRUDER ALARM SYSTEM:
Now it’s completely ready for the use. So, whenever the light is being intruded then alarm will go on along with the LED.
OFF CASE OF VISIBLE INTRUDER ALARM SYSTEM
ON CASE OF VISIBLE INTRUDER ALARM SYSTEM
This is the final stage of the making process of Visible intruder alarm. we hope you will made is project.
This is Enamul Hassan, an Electrical and Electronics Engineer. I love discovering new things. I share my knowledge in this blog.