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Line Follower Robot

 Category: Electronics Brief Description The working of a line follower Robot is based on concept of sensing the white/Black line and accordingly controlling the motion of the Robot. To sense the line we need line detecting sensors and circuit to control motor using these sensors. In this tutorial we will be implementing a white line following robot.
Concept

Welcome to Drmz World! This mini tutorial will guide you how to make your own line follower Robot that too using with simple electronic components and Bread Board. The working of a line follower Robot is based on concept of sensing the white/Black line and accordingly controlling the motion of the Robot. To sense the line we need line detecting sensors and circuit to control motor using these sensors. In this tutorial we will be implementing a white line following robot.

To start with let us make a list of components to be used:
 Components Quantity 1. BreadBoard 1 2. LDR 2 3. LM324 1 4. ULN2003 1 5. POT (10k) 1 6. Resistance (10k) 2 7. Resistance (1k) 2 8. Resistance (220 ohm) 2 9. LED (Red) 2 10. White LED 2 11. 9V battery 2 12. Battery Caps 2 13. Robotic Chassis 1

Sensors

To detect the white line we will be using light detecting sensor which is in our case a LDR (light dependent resistance). The LDR is a kind of variable resistive sensors whose resistance value increases with increasing light intensity. However the working of a simple LDR is Analog in nature. Working and controlling analog signals are difficult. Hence we will be creating a sensor circuit which will be converting analog signals to digital signals which are easy to handle and work with.

LDR circuit: (Resistance variation conversion to Voltage variation)

As discussed above, LDR works on the principal of resistance variation with change in light intensity. Our main task is to covert this resistance variation to voltage variation, so that later we can convert it to digital logic. This can be easily done by using a series circuit as shown below :

To understand the working of above circuit, let us take a small example. Let us consider that resistance of LDR varies such that in light condition R (LDR)=5k and in No light condition R (LDR)=15k and series R=10k. So what will be Voutput ? Applying simple formulae of Voltage divider rule we find that Vout (light)= 3.33 and Vout (No light) = 2 Volt. Thus we now get voltage variation for light variations. If we want to convert these two values to digital values, we need to call lower value as zero and higher as 1. To convert this we need to set a threshold value which using a comparator will convert our analog voltage to digital logic.

LM324

It is an Op-Amp IC. Op-Amps or Operational Amplifiers are digital ICs which are used to amplify analog and digital signals. Op-Amps work in two modes, one Open loop mode, two close loop mode. We will be using Op-Amp in open loop mode. Op-amps when used in open loop mode, act as a analog comparator. Any general Op-Amp has two inputs designated by + and - pins. And one output as shown below:

The working of the circuit is like if we give higher voltage to + Pin than - Pin, the output voltage is + Vss or High. Conversely if we give Lower voltage to + Pin than - Pin, the output voltage is -Vss or low. Thus we can use Op-Amp to convert a analog voltage to digital by giving analog voltage to + pin and threshold value to - pin. If analog voltage is more than this threshold value than output is high or 1 and conversely if analog voltage is less than threshold value than output is low or 0.

Circuit Diagrams