Photon: A Simple Analog Line Follower

The robots that I build do not stay for long as I dismantle them and use their parts to build other
projects. Actually I do that to save money and whenever my friends ask me to show some of my robots, I am left with nothing. So I decided to build a permanent robot that I can show to my friends and relatives if they ask me to do so. I wanted to keep the robot as cheap and simple as possible so as to not hamper other projects. I decided to build a simple line follower as line followers, though simple, are very entertaining to watch.


Photon had to be cheap so I decided to use LDRs and LEDs to build a line sensor. The principle behind its working is very cheap, white reflects light whereas black not so much. I used white LEDs to allow Photon to follow any colored line on a contrasting surface. 


I used geared motors in Photon because they are cheap, provide sufficient torque and draw sufficiently small amounts of current under load.


I had to keep the main circuit cheap so I decided to use a voltage comparator as they are accurate compared to transistors and can operate at variety of voltages. I used 2 TIP122 transistors as motor drivers. I also added 2 potentiometers to control the sensitivity of the sensors. This allows photon to travel on a wide range of tracks with contrasting colors. 

Power Supply

At present I am using a 9 volt battery to power photon but I will upgrade to a rechargeable Ni-Mh battery pretty soon.

I am still working on the chassis. I want the chassis to be small and light. I am trying to modify old lunch boxes and sweet boxes but I have not yet found a perfect case. I have spent about Rs.220 
(close to $3) on photon so far as I already had the motors. With the motors photon will still cost less than Rs.500 (close $7). Ni-Mh battery may add to the cost a little but it will be a one-time investment.

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