Design

For the design of the line robot I will be using a plastic container that I found at a thrift store for a dollar. I plan on putting the two motors towards the rear of the container with the caster wheel at the front using some L brackets to connect them together. The design will be similar to the one that was used in the manual. I will have the sensor board towards the front with a cutout at the bottom so the sensors can read the floor. The container I have chosen is listed below along with a picture of it. I chose this since it’s clear and I would like to see the "guts" of the robot. I think it's a cool look and I could add some LEDs inside to make it look a little cooler in my opinion.

Material List and Cost

For this project I ordered some of the parts online. To start I bought an Arduino clone on eBay from a seller named 16hertzelectronics. The price for this Arduino Uno was $14.99 with free shipping.  The link to the Arduino is:

http://www.ebay.com/itm/UNO-R3-Kit-Starter-to-Ultimate-Arduino-Compatible-LCD-Breadboard-Sensor-/271658490668?pt=LH_DefaultDomain_0&var=&hash=item3f401b9b2c

This Arduino also comes with a few other things like LEDs, jumper wires, resistors, a breadboard, and the USB to connect the Arduino to a computer.

Another thing I bought was a motor shield to run the motors from Adafruit.com. The cost of the shield was $19.95 plus a shipping charge of $9.18 which totals it to $29.13. The link to the shield is:
http://www.adafruit.com/product/1438

I also needed IR sensors to read the ground so I ordered 5 from digikey.com for $1.26 each. The shipping for the sensors was $2.68. The total cost for the 5 sensors with tax and shipping came out to $9.36. The link to the sensors is:
http://www.digikey.com/product-search/en?lang=en&site=us&keywords=tcrt5000l&x=0&y=0

The next thing I needed was the motors that will be running the Line Robot. I ordered two servo motors from hobbypartz.com for $7.49 each. Shipping was $6.95 and total price for the servo motors was $21.93. These servo motors will be later modified to obtain dc geared motors. The link for the servo motors is: http://www.hobbypartz.com/43gexiseb11.html

I bought a small perforated board from RadioShack for about $3.50. I also bought a 5-pack of 10K ohm resistors at RadioShack and two 5-packs of 150 ohm resistors. Each pack cost about $1.50. So that's a total of $8 at RadioShack. Also needed some wires to wiring the resistors and the sensors together to make connections between the Arduino, the shield, and the sensor board that we will be making. I also bought a 5K linear taper potentiometer from RadioShack for $2.79 to be used to control the speed of the line robot. And also a solder iron from Harbor Freight for $4.23.

For the frame you can pretty much use anything that can fit all the components of this project as well as being able to mount the two motors on the side of it. To find the frame you can go to a thrift store and find containers or toys for the frame and to find the two wheels that the two motors will be powering. The price will vary but it should just cost you a few dollars or less.  I found this container for a dollar and it seems that everything will fit in if I cut out the plastic divider in the middle. I found the wheels from an old mega block toy that I had, but I might still look around for wheels that are a little larger. You also need a switch to turn on and off the line robot. I had two from a previous project that I did a while back. The switch should be a SPST switch. You can get one from RadioShack for a couple dollars or less.

So far the total price of the project is now $95.37. You can save money if you have some of the parts from previous projects like the motors or the shield. I also learned that you can find IR emitter/detector boards already premade for about the same price that I spent for the sensors. But I went ahead and made the board so I can have the learning experience of soldering and making a circuit.

You also need some nuts and bolts -- about 20 bolts with nuts -- to make the robot sturdy or you can also use zip ties to mount some of the components.  You can buy the nuts and bolts at a hardware store like ACE hardware or at Walmart. I bought a pack of 17 screws with nuts for a dollar at Walmart and bought the caster wheel at Walmart for $2.94. I also got some electrical tape that can be used for the track when the project is completed. 

To power this project I will be using regular AA batteries to provide the needed voltage for the motors and the Arduino. You can use rechargeable batteries if you come across a good deal on them.