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  • Basic Line Follower Toy Car

  • Created: May 27, 2016

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A line follower car/robot is a very common project nowadays. A lot of different versions are available in the market and in the internet. This line follower is designed to have very least possible components making the whole project very small depending on its physical design.

An infrared LED is installed facing down at the center of the car, then the reflected light from the IR LED is fed back to the two phototransistors. The phototransistors will send a voltage signal to the inputs of the MCP602 dual op-amp that outputs a current, which varies depending on the phototransistors. These current will affect the BJTs to drive the motor connected to it. If the voltage signals from the two phototransistors are the same, the motors will rotate at the same speed, otherwise, the motors will run differently causing the car to turn. When the car is on the curved line, one of the phototransistors is out the line, and the other is going into it. The signal from the phototransistor that is out the line has a higher voltage than before because it's resistance has dropped down, then the op-amp sends a bigger signal to the transistor and the motor of it's side goes faster, turning the car back into the line.

We can also modify the car to follow a white line on a black background, just swap the position of the phototransistor and the reference resistor, now the phototransistor has the emitter connected to GND and the collector to the resistor and the input of the MCP602 op-amp. This minimalist project can be further modified into much bigger projects that include more components like microcontroller.



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