INFRARED(IR) Transmitter(TX) And Receiver(RX) :

INFRARED(IR) Transmitter(TX) And Receiver(RX) :

INFRARED(IR) Transmitter(TX) And Receiver(RX) :

IR LED

IR pair is an electronic device which consists of two parts i) Transmitter and ii) Receiver. Transmitter is used to transmits or emit  the INFRARED rays and the receiver is used simply to receive these radiations . Sounds simple and easy  .

Transmitter is often known as IR LED and the Receiver  as IR Sensor.

How To distinguish Between these Two ?

• Connect cathode of one LED to +ve terminal of DMM
• Connect anode of the same LED to common terminal of DMM
  (means connect LED such that It gets reverse biased by DMM )
• Set DMM to measure resistance upto 2M Ohm.
• Check the reading.
• Repeat above procedure with second LED.
• In above process, when you get the reading of the few hundred Kilo Ohms on DMM, then it indicated that LED that you are testing is IR sensor. In case of IR transmitter DMM will not show any reading.

Simple Testing Circuit:

Make connections as shown in the schematic below.

 

IR pair Test Circuit

The pair should face each other in an Head to Head manner and the distance b/w these should be as minimum as possible , but please make sure that there should be a small clearance b/w  pair.

Observe the Following:

• When there is no obstacle b/w the two the RED LED will start glowing.
• When there is an obstacle b/w the two the RED LED will stop glowing.

Conclusion:

• In the case , when the Infrared is reaching the receiver (Rx), the Rx would show the minimum resistance, ideally it could be  Zero Ohms (or Short Circuit).
• In the case , when there is an Opaque obstacle (say Black Plastic Piece or the faces of the Pair are rotated) b/w the two , and the Infrared is not reaching the receiver (Rx), the Rx would show the maximum resistance, in the range of few Mega Ohms , Ideally could be Infinite Resistance (or  Open Circuit).