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How to make an Entry Detector using IR Sensor?

Entry Detector Project Description

IR primarily based protection alarm circuit can hit upon any movement and cause the alarm when a person enters a room. This circuit is very useful in homes, banks, shops, restricted regions in which an alert alarm is needed on any motion. This circuit is primarily based on IR sensor where an IR beam is continuously falling on a photodiode, and whenever this Infrared beam breaks, by means of any type of movement or if anyone enters the room, a buzzer is triggered.

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How IR Entry Detector Works?

While the IR radiation is falling on Photodiode, the voltage at the output pin of the IR Sensor is HIGH which will ring the buzzer. While the IR radiation is not falling on Photodiode, the voltage at the output pin of the IR Sensor is LOW which will turn off the buzzer.

Now How will you Turn ON and OFF the buzzer when you open or close the door? Lets Check it Out…


  • IR pair (IR LED and Photodiode)
  • Buzzer
  • BreadBoard
  • Double Sided Tape

IR Sensor Explained

IR sensor is composed of an IR LED and photodiode, in which IR LED emits IR radiation and photodiode detects the radiation. Photodiode conducts current inside the opposite direction, on every occasion, IR falls on it, and the voltage across it changes, this voltage alternate is sensed by photodiode and generates output accordingly.

IR Entry Detector Project Tutorial

Steps to Make an IR Entry Detector

Step 1 – Getting the Components from LCSC

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Firs thing to do is create a free account.

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However, an account is not mandatory for ordering from LCSC website. But it makes it easy for you to buy things from LCSC in the future.

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Now you can search for the component you want in the search box.

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You can apply various filters which will make it easy for you to find the components you are looking for.

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Add to Cart

Once it is done, you can add the components to your cart. Make sure you select the right quantity.

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Check Out

If you have added everything you need to the cart, you can now proceed to check out.

Placing the Order

On the next page, you have to provide the delivery address, the shipping info, and payment information.

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Receiving the order

The components will be packed and shipped within days and will be delivered to your doorstep within the mentioned time period.

There is an order details page, where customers can see what stage their order is at, all the way from the order submission to the final delivery process. 

Step 2 – Connections

IR Sensor Pinout

  1. VCC (5V) – VCC will power up the sensor circuit
  2. GND (0V) – Negative Terminal of the battery
  3. Vout (Output Voltage) – Output voltage is taken through Vout pin when IR rays are reflected back to the photo diode.

Here I will bend the legs of LED and photo diode so that they are facing each other. I will show you in the procedure.

Circuit is pretty simple. All you have to do is fix all the components like shown below on the breadboard.

IR Sensor
Vcc – 5V
Gnd – Gnd
Vout – +ve of Buzzer

+ve – Vout of IR Sensor
-ve – Gnd

Step 3 – Setting up the Detector

Clean all the connection using a zip tie and this is what it looks like.

IR Sensor Burglar Alarm Neat

Now we can fix this on the door frame and power it up.

Now we need something to block the IR rays from LED from reaching the photodiode. For that you can use a black cardboard or a tape.

IR Sensor Burglar Alarm
IR Sensor Burglar Alarm

We can fix this on the door in such a way that when the door is closed, it will be placed in between the photodiode and the IR LED.

Step 4 – Test

Now power on the circuit and try opening and closing the door.

When the door is closed, the photo diode will be facing the black surface and no IR rays will be reaching the photo diode. Hence the output of the IR sensor will be Zero.

When the door is opened, the photo diode will be facing the IR LED and the IR rays will be directly hitting the photo diode. This will cause the output voltage go high and the buzzer connected to the output of IR sensor will start to beep.

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