retrointerfacing

As presented for the first time on FAB6, using a Sharp gp2y0a02 sensor the flatpack-walker just got a little bit smarter. As long as the distance sensor is triggered, the robot walks backwards.

The code is still pretty simple:

// avoid obstacles using Sharp G2P sensor on Analog 0
#include <Servo.h>
Servo frontservo,backservo;
char walkpattern[] = {60,100,100,100,100,60,60,60};
void setup(){
  frontservo.attach(9);
  backservo.attach(10);
}
void loop(){
  for(int n=0;n<4;n++){
    if(analogRead(0)>500){
      frontservo.write(walkpattern[2*n]);
      backservo.write(walkpattern[(2*n)+1]);
    }
    else{
      backservo.write(walkpattern[2*n]);
      frontservo.write(walkpattern[(2*n)+1]);
    }
    delay(200);
  }
}

http://www.protospace.nl/content/protospace-novu-editie-nl-rtl4 -> see the flatpack walker in action on dutch television - it has also been submitted in the unlimited design contest http://unlimiteddesign.nl/en/node/44/6
It is being used in the fablabtruck: http://www.fablabtruck.nl/nl/fablabtruck/lesprogramma.html
Also on idealize (read interview) http://www.idealize.nl/2009/09/udc-2009-edwin-over-simplewalker/

Joris van Tubergen (protospace) talks about the robot in this interview (see vimeo)

So much for the ‘paws’, on to the whiskers. I used old guitar string which is very flexible (but does not permanently deform that easy) so it stays in shape nicely. The switch is made out of one loop of wire which normally does not touch the feeler-wire. As soon as the feeler is bended by an obstacle, it will touch the loop, making electrical contact.

The wiring to the arduino or ottantotto is quite easy too. See the schematic below:

A resistor and LED are soldered at the positive side. As soon as the switch makes contact, the LED will light up, and a low (0) will be sent to the microcontroller.

Okay.. by common consent my simpleWalker has been dubbed flatpack walker according to hack a day. Who am I to disagree.. It got posted on hack-a-day after my first-time-ever ‘instructable‘ I posted on this topic.

At the protospace fablab I made a laser-cut wood version of the simpleWalker. It took only 5 minutes on the laser cutter, instead of an hour behind the bandsaw! I used 4mm birch plywood.

The robot works well (and smells like a campfire … oh well…)

Again, it can be seen walking on YouTube (but with a lot more noise than the silent rubber feet used in previous versions)

In the first version of the simple walker I used a custom atmega32 based board. I replaced it by a ‘custom’ version of the Arduino which I dubbed ‘ottantotto’

The microcontrollerboard is a breadboard version of the ‘ottantotto’ controller. It uses an ATmega88 instead of mega168 (mostly because they are cheaper, they sell for <2 eur at ledsee.com). This required altering the bootloader, arduino hardware-cores directory and file 'boards.txt'. Read more details and download the bootloader from the wiki.

In some cases disturbance on the powerlines by the RC servo’s can cause the microcontroller to ‘freeze’. The capacitor I originally mounted is probably to small.. Adding an external 1000uF cap seems to solve the problems.

In the meantime I also made an arduino-sketch instead of the WinAVR gcc sources.. It is staggeringly simple:

#include <Servo.h>
Servo frontservo,backservo;
char forward[] = {60,100,100,100,100,60,60,60};
void setup()
{
frontservo.attach(9);
backservo.attach(10);
}
void loop()
{
for(int n=0;n<4;n++)
{
frontservo.write(forward[2*n]);
backservo.write(forward[(2*n)+1]);
delay(300);
}
}

on breadboard a simple programming dongle has been made (using a max232) which can be used in combination with an usb-serial adapter cable (or a plain RS232 cable) to program the board. It is fully Arduino compatible. Schematics can be found on the ottantotto wiki page.

The simple 2-servo walker (which I hope to use as a fablab-ready robot kit) went through its first paces today. The microcontrollerboard used is an ATmega32.. my ‘ottantotto’s haven’t arrived yet

The robot walks well, now it’s time to make it turn, avoid obstacles, sit up, make noise, etc… You can see it walk on Youtube

If you want to build your own: see the previous post on construction details. You have to get some parts, such as two RC servo’s, 4 AA batteries, battery container, microcontroller board, etc..

Then you have to make the mechanics. Here is a pdf which you need to cut or saw out of a sheet of polycarbonate, perspex, plywood .. walker