I have always been fascinated by robots especially one with the wheels because they are cheap, easy and fun to make and play around with. Recently I came across a circuit in one of the books. It was a light sensitive led circuit based on 555 timer ic. I modified the circuit just a little to make a cheap light seeking robot. Let's see how i did it.

Step 1: Materials

To build the bot you will need the below mentioned components.
1. 2x 555 timer ics
2. 4x 10k resistors
3. 2x LDRs (Light Dependent Resistors)
4. A breadboard if necessary
5. Some wires
6. 2x motors (with wheels)
7. 2x 0.01n capacitor
8. 9v portable power supply

And you may also need a messy workbench.

Step 2: The Schemetics

The schematic diagram of this robot is very simple to understand. As I had mentioned earlier I just modified a circuit from on of the books to create this one. Make sure that the motor you use DOES NOT draw a lot of current.

Step 3: Chips on the Board!

Insert the ICs as shown in the figure. There will be a small notch or dot on every 555 timer ic. Make sure that the dots on both the chips should face upwards if you are going to build the robot as per the breadboard layout given in this instructables. Connect pins 8 and 4 together. Then connect pins 6 and 2 together.

Step 4: Power Source Layout

Connect pin1 to the negative rail on the breadboard. Connect pin8 to the positive rail on the breadboard. Do the same with the second chip.

Step 5: Resistors!

Now the most important part. Connect a 10k(brown, black and orange)resistor between the pins 8 and 6. Connect one more 10k resistor between the pins 7 and 6. Do the same with the next chip.

Step 6: Capacitors

Now connect a 0.01uf capacitor between the pins 1 and 5 of both the chips.

Step 7: Sensors

The sensors used in this robot are nothing but simple LDRs. LDR is a kind of resistor whose resistance varies according to the intensity of the light falling on it. Connect the LDRs between pins 1 and 2 of both the chips. You can connect LDR either way as it does not have polarity.

Step 8: Conclusion

Now, last but not the least. Connect your motor between pin3 of the chip and negative rail of your breaboard. Do the same with the second chip. Its all done! You have built a light seeking robot yourself! Connect a 9v battery and shine a torch over the LDRs. You will notice that the motors run! Place the motors in such a way that the LDR controlling it is in the opposite side. The LDR controlling the right motor must placed to the left

Step 9: Troubleshooting

If this project is your first electronics project then you may have some problems. Here are some tips to ensure that your robot works best.
1. Make sure that your connections are correct before applying power. (Use the schematic diagram because as this is my first instructables I was very excited and took the photos in a hurry and there might be some errors in the connection.)
2. Confirm whether your components are working properly before using them.
3. Use a low power consuming motor.

Enjoy!