TSOP based IR Sensor

In this article I will discuss about more advanced IR sensor as compared to the one proposed in previous article. It provides accurate results even in sunlight and is not affected by surrounding light sources.

Simple IR Sensor has a disadvantage that it gives false detection when used in presence of sunlight. We can make more complex IR sensor which is able to differentiate between IR light from its own source and sunlight or any other light from surrounding light sources. Here I am going to introduce TSOP based IR Sensor.

Basic Idea :

In simple IR sensor (link) an IR LED is used to transmit a continuous beam of IR light and a Photo Diode is used to detect reflected light from any surface (surface can be of any obstacle or floor when we are using this sensor in line follower robot).

In TSOP based IR Sensor a modulated IR light at selected frequency is transmitted and a receiver is made that would only detect light of the same frequency, filtering out light of other frequencies.

TSOP is a miniaturized receiver for infrared remote control systems. It consists of a PIN diode and a pre-amplifier in a single package. Output of TSOP is active low. As shown in figure ambient light is filtered out by the epoxy package and then the output of PIN diode is amplified and pass through a band pass filter. The output of TSOP can directly be connected by any I/O pin of microcontroller.                                

There are various TSOP available in market cantered to different frequency —

For example – TSOP1736 can detect light of 36 KHz frequency and TSOP1740 can detect light of 40 KHz.

Here I am taking TSOP1736 to make TSOP based IR Sensor module.

Circuit of Rx :-

In the above circuit 100 Ω resistance and 4.7 µF is connected to suppress power supply disturbances. An LED is connected at the output pin of TSOP to indicate the logic level.

Circuit of Tx 

To transmit light of 36 KHz frequency we can generate that frequency by using any microcontroller, oscillator or by 555 timer IC. Here I am using 555 timer in astable mode to generate a square wave signal to drive an IR-LED at a frequency of 36 KHz.

In the astable mode, the frequency of the pulse stream depends on the values of R1, R2 and C1:

So as I am using TSOP-1736 that has central frequency of 36 KHz, I choose –

• C1 = .022 µF (Polyester Capacitor 2A223J, 100 v)
• R1 = 620 Ω
• R2 = 603 Ω (560 Ω + 43 Ω)

which gives a frequency of 35.846 KHz.

A potentiometer R is used at the output pin of 555 timer IC, by which we can set the intensity of IR LED.

 PCB Layout :-

If you want to increase the range of this module, you can increase number of IR LEDs. I tried and it gives positive results.