Step 13:

Connect one terminal of each motor with each other. Connect this common wire with positive terminal of another 9V battery. Connect negative terminal of battery to Ground. Connect free terminal of one motor to PIN16 of ULN2003 and free terminal of another motor to PIN10 of ULN2003. See figure:



Now you can verify our robot using natural light. As we rotate the knob of potentiometer, one state comes when switching of LED takes place. LDR accepts the light from surrounding so that output is 1. We have to adjust potentiometer so that the LED just switch on. When LDR is covered by hand, the output becomes 0. Adjust both potentiometers so that sensors respond according to the light falling on it, i.e., output is 1 when light falls on LDR and output is 0 when LDR is covered.

Step 14:

Remove the directly connected LDRs and connect them through separate 4 pin connectors so that you can place the sensors at desired places. See figure:



Step 15:

We do not want to sense the natural light. The sensors are placed below the robot facing to the floor. For light we use superbright LEDs. Connect these LEDs with 100 ohm resistances as shown in figure:



Step 16:

Finally, we have to place our circuit on the chasis. Remove the upper part of chasis so that it looks like the figure given below:



Step 17:

Finally, place the breadboard on the chasis and fix the sensors as shown in figure:



This is your final robot looks like. Now cut strips of white sheet of width about 5 cm and make a loop on black sheet. Test your robot on this arena and troubleshoot the problems.