Hello everyone, I took enough in this community, but never had done any publication, and this is my first time. I apologize in advance for mistakes, and openly I receive your criticism and comments.

The idea of this project was born one year ago, with a contest of following line robot, taking the idea of the website (http://wannabe-programmer.blogspot.com/2013/10/rob...), appreciative of the contribution of the program for Arduino based on a PID.

Then the realization of the circuit takes place in breadboard, performed only design pcb sensors, based on QTR-8A of Pololu.

Step 1: Suplies

Software:

- PCB Wizard

- Arduino IDE

Hardware:

- 1 x Arduino nano

- 8 x CNY70

- 1 x L293D

- 34 x Pin headers female, 9 x pin headers male and 20 x pin headers right angle

- 1 x DIP Base 16-pin

- 2 x Terminal block 2-pin

- 1 x Button

- 2 x Jumper

- 1 x Micro switch

- 2 x Resistor (1k ohm and 220 ohm), 8 x SMD resistor 220 ohm, 8 x SMD resistor 47k ohm and SMD resistor 0 ohm

- 1 x Led (bi-color)

- 1 x NPN transistor TIP31C

- 14 x Jumper wires

- 2 x Motors 3.6v - 12v

- 1 x Old cell phone battery

- PCB copper, ferric chloride, toner print, photographic paper, spray varnish, clamps, wire cutter, hot glue silicon and Dremel

- Optional 1 x Boost converter 3.6v - 12v

Step 2: PCB Design

The software I use to design my PCB is PCB Wizard, for its simplicity of use. With this software I created my designs, pulling me from various troubles. There they can find common devices, or by adding them as SMD resistor libraries, but those who are not will have to be designed from the device and measures of this.

The first was the design that made the sensor module, basing on the module Pololu - QTR-8A, using CNY70 reflectance sensor and SMD resistor to use less space.

The main board is my design, taking as a control Arduino nano, the motors can be fed from the main source or separately (boost converter) which depend motors are chosen. Finally we will proceed to verify that everything is in place, and none of this overlayed devices.

Here they can find the designs of the two PCB.

Step 3: PCB Assembly

When he was ready designs, it was time to pass them PCB copper, the method I use is the toner transfer, getting good results. Use photo paper for designs, it falls well with water.

When the design is taken into PCB copper, it is verified that there are no lines unbound, and proceeds to place it in the ferric chloride providing a heat source to accelerate the process. When this leave we will proceed to drill and place the devices to weld.

The end I like to put a layer of varnish, this helps not rust copper for time and improved aesthetics.

Step 4: Motors, Power Supply and Connection

The motors I've used are 3.6v, recycled from an old toy. These come with their own gearbox, making them perfect for my project.

For the management of these use the integrated circuit L293D, which has two bridges H independent, and having a good performance for handling small motors. This circuit offers a separate supply of motors to about 36v.

The power supply was using an old cell phone battery, providing 3.6v.

The connection to the sensors use jumper wires, facilitating any change, these are activated by the transistor TIP31C.

Step 5: Arduino Program

Program I used is not my property, using the above mentioned at the beginning of this. The program is based on a control PID (proportional, integral and derivative).

The operation of the sensors was carried out with Arduino library QTRSensors, giving the option to calibrate and choose number of sensors and samples.

He operation of the program is to keep the robot on the black line or white and move it as quickly as possible, preventing it running off.

I leave the library and the program Arduino.

Step 6: First Test

This is the first test to check that everything works correctly, pressing the button sensors are calibrated to the line, and give him a second time, this begins its journey.

Step 7: Final Design

The structure is made with thin cardboard, but first let her longish. After cutting it, fill it with foam, since it is light does not add any weight. They were added Lego wheels for more contact on the track.