Simplest Line Follower Robot

a few days ago, i saw a robot at...
https://www.instructables.com/id/INTRODUCTION-24/

to be honest, the circuitry was a mess to see, although the schematic was simple, so i made a new PCB of it, and redesigned a little things, to get a very neat and small circuit of it....

this circuit needs:-

1.LM358 op-amp chip
2. 220 ohm resistors  x  4
3. 1k resistor    x  2
4. BC547B transistor (NPN)  x  2
5. white LED    x  2
6. orange LED   x  2
7. 3 or 6V DC geared motors  x  2
8. copper clad circuit board or protoboard
9. 20k pot   x  2
10.5k pot   x  2
11. photo-diode   x  2
12. 9v battery
13. 100uf capacitor

i have given the circuit design [an eagle file], for making the PCB, you can adjust the space between the sensors in the design as per your requirment...

my robot's body is not so good, but it can work on any body, its is a very easy project to make... although it needs a little adjustments in the potentiometers, the first time... enjoy... :)