DIY Simple IR Sensor Using 555 Timer

In this tutorial, I will create an IR sensor by using IC 555 Timer with simple steps. The operation of this IR sensor is so simple when an object is in front of the sensor, led will light up. We have two IR LEDs, a transmitter and a receiver. When the current passes through the transmitter led, it will emit IR rays. We can see these IR rays by using any mobile or any other camera device. 

The receiver is used in reverse bias and is used to capture IR rays. The cathode(-) of the led is connected to the source (+) terminal. Being in reverse bias, the receiver will allow, in its initial state a small current to pass through it. When an IR ray falls on the receiver, it will allow a higher current to pass through it. Here we will use a 555 Timer IC.

Circuit Diagram

infrared sensor

Components Required

  • 555 Timer IC
  • IR Transmitter
  • IR Receiver
  • BC547 transistor
  • BC557 transistor
  • 10 uF/25V Capacitor
  • Led
  • Resistor (1 KΩ, 10 KΩ, 22 KΩ, 220Ω) 
  • Piezo Buzzer
  • A Switch
  • 9v Battery

Circuit Connection

In this IR sensor project, we will put the IC 555 timer IC on the breadboard. And then we should connect pin 8 to the collector of the BC557 transistor and pin 1 to the ground. Next, the base of BC557 is connected to the collector of BC547 transistor through a 1 KΩ resistor. Another terminal of BC557 i.e emitter is directly connected to Vcc.

The base of the BC547 is connected between the cathode of the IR receiver and a 10 KΩ resistor. And another emitter part is connected directly to the ground.

Next, Pin 7 of the IC is connected between a 1 KΩ and a 22 KΩ resistor and it is connected with pin 6 through this 22 KΩ resistor. 

Pin 6 and pin 2 are connected with each other and a 10uF capacitor from pin 6 is connected to the ground.

Finally, the IR receiver is connected to the base terminal of BC547 with its cathode terminal this terminal is also connected to the ground through a 10 KΩ resistor. Its anode terminal is connected to Vcc. 

The IR transmitter is connected with Vcc with its cathode terminal and the anode terminal is connected to the ground through a 220 Ω resistor. 

The output from pin 3 of the IC is connected with a buzzer and another terminal of the buzzer is grounded.

Working of IR Sensor

In the above IR sensor circuit diagram, we should note that transistor BC547 is an NPN transistor and transistor BC557 is a PNP transistor. BC547 will be in an active mood when a positive voltage is applied to its base and the BC557 will be in an active mood when a negative voltage is applied to its base. 

When the whole circuit is turned on, the IR transmitter starts emitting infrared rays, which falls on the IR receiver and a potential difference will create across the IR receiver which turns on the transistor BC547, which further turns on the transistor BC557 through collector and base. Then the transistor BC557 starts to conduct Vcc supply to pin 8 of the 555 timer IC which turns on the 555 timer IC.

In this IR sensor project, the 555 timer IC is configured in astable mode. The output from pin 3 by turning on the circuit which is shown by a buzzer is activated for a particular frequency. This frequency of buzzer’s beeping can be determined by the given formula 

Output Frequency = 1.44/(R1+2*R2)*C1

Where R1 represents the resistor between pin 7 and pin 8 i.e 1 KΩ resistor and R2 represents the resistor between pin 6 and pin 7 i.e 22 KΩ resistors. C1 represents the capacitor between pin 6 and ground of the 555 timer IC i.e 10 uF.

Application of IR Sensor

An IR sensor can quantify the warmth of an item just as it distinguishes the movement.

These sorts of sensors measure just infrared radiation, instead of discharging it that is known as an inactive IR sensor.

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