Tuesday, February 26, 2013

Lets Design Line Sensor for Line Follower Robot

Robometricschool. - In this time we want to share with you about how to design line sensor that be usually used in Line Follower Robot. We want to design line sensor using main component IR LED and Photo-Diode. Beside using LED IR and Photodiode, you also can design line sensor using Photo-reflector.
Figure 1. Line Sensor when not get infra red light

As we know that line sensor can be used as line sensor in line follower robot. Infra Red LED or called IR LED will transmitte infra red signal to photodiode. IR LED will transmitte infra led when any current that flow to this component. This work like DIODE, but specially to transmitte infra red light not visible light.

Figure 2. Line Sensor when get infra red light
Other component is photodiode as reciever of infra red signal that transmitted by IR LED. Photodiode is a type of light-sensitive sensor (photodetector). Photodiode current will flow which forms a linear function of the intensity of the light received. These currents are generally organized on power density (Dp). Comparison between the output current with a power called the current density responsitivity. Flows in question is the leakage current when the photodiode is exposed and in forward biases.

Here is the relationship between the photodiode output light intensity received when get forward biases is forming a linear function like in figure 2 below:



Figure 2. Photodiode output relationship with the intensity of light

Line Sensor Working Mechanism

You can see mechanism of line sensor principle when it sensor detect line in the floor like in figure 3 below:

Figure 3. Line Sensor Working Mechanism

Work Priciple of Line Sensor 

We will divide work principle of line sensor into two part there are when sensor get infra red light and when sensor not get infra red light.


  • When sensor not get infra red light
When photodiode not get infra red light, it will make the resistance value can be assumed to be large or infinite. So there is no leakage current that flows into the comparator like in figure 1. above.


  • When sensor get infra red light

When photodiode not get infra red light,the photodiode will be a source of voltage and resistance value will be small, so there will be leakage current flowing to the comparator like in figure 2. above. 


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