TCRT5000

The TCRT5000 are reflective sensors consisting of an infrared emitter and phototransistor. The TCRT500 sensor is simply a combination of a photodiode and a phototransistor. These sensors are enclosed in a leaded package that blocks visible light. This TCRT5000 photoelectric switch is ideal for a wide range of applications such as line tracking robot cars like DIY projects.

In this, the sensor is powered through a current limiting resistor of value 220R, and the Transistor is also grounded through a 10K resistor. The biasing of the transistor is controlled by the amount of IR light it receives as it does not have a base pin. This sensor worked as either an analogue sensor or a digital sensor. In case we have to only detect the presence of an object, then the sensor works as a digital sensor. Moreover, if the distance of the object should also have to measure then the sensor is used as an analogue sensor. This sensor functions to detect the presence of an object or any other reflective surface in front of it. Also with some level of programming, it can also calculate the distance of the object in front of it.

One major drawback of  IR sensors is that they are easily affected by environmental conditions. The phototransistor reacts to the IR light from the photodiode as well as to the IR light from Sunlight, house lightings, and other commonly available sources. This problem is normally solved by performing noise cancellation in the program. By controlling the photodiode through a GPIO pin of the MCU/MPU, we can turn off the diode. Thus by checking the noise value in the phototransistor, we can turn on the photodiode. By measuring the change in values by nullifying the noise that was present while the diode was turned off.