Rustic Engineering

My Mind working on…

GUI v1 – part 1

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GUI v1 is little robot I was design over the last months. I have already made some other robots, but I don’t even finishing most of them. This design has various issues, and challenges. But it’s almost finished. Now I’ll post some steps of your design and construction. If you like it, visit my project page a LetsMakeRobots. It’s a awesome site with a lot of robots and good people.

First, going to my desires: I want a little robot, with little wheels and little motors. They need to be battery powered, but a little battery.

Some things I want my robot to do:

  • Line following;
  • Maze resolve;
  • Wireless communication;
  • USB wired communication;
  • Self-charge your battery;
  • Have a lot of LEDs (because LEDs are fun!);

So, with this great inspiration I begin it’s prototype. Maybe what I said now sounds a little amateur, but, when I have started, I don’t have a clear idea of how the final robot looks like, but I knew that your lines should be clear, without wires growing up.

I hate deals with hardware, so I decide that for the robot body I want use a PCB. The initial result was good enough to encourage me:

GUI PCB Based Body

Now, the nightmare begin: solder every part to PCB and wire all. I like, but I hate this.

The robot have the follow parts:

  • PIC18F252 was MCU, running at 20MHz;
  • 7 reflectance sensors, QTR-1RC;
  • Dual Motor Controller, TB6612FNG;
  • 2 Micro Gear Motor 30:1;
  • Step-Up converter, NCP1400 for 5V;
  • 3.7V LiPo battery;

About the MCU:

The PIC18F252 has the PIC Tinybootloader inside, for speed up the code development. Bootloaders have their issues, but my design is for a robot with easy upgrade capabilities. I like that everyone how like to change their software, can do this without bought a PIC programmer.

I don’t use all pins, but a think that for the final version, some other PIC is a better choice (like PIC18F452).

About the sensors:

The reflectance sensors are the QTR-1RC from Pololu. They have a QRE1113GR, that is a emitter-receiver pair. Pololu sells this sensor with two versions, one digital and other analog.

The digital version translates the reflectance into the capacitor discharge time, so with a common digital I/O port, and a counter, you can differentiate from a  White surface (more reflective) from a Black surface (less reflective).  The circuit below is show their use with a ordinary digital I/O on the MCU:

Reflectance Sensor - Digital Use

The analog version (QTR-1RA) needs a ADC line on MCU. Most of MCUs today have one, so don’t worry about your choice.

Now I have to sleep. Tomorrow I’ll post the next steps. Bye.

Written by forrequi

September 7, 2009 at 04:21

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