retrointerfacing

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

This is a try-out of a FabLab-ready kit design for a 2-Servo walking robot. The design is inspired by the lynxmotion kits and the designs by david buckley. The goal for this project is to make all mechanical parts for the servo walker out of 1 A4 size sheet of plywood (or perspex, lexan, delrin, whatever).

Two RC servo’s are mounted in the appropriate holes, Battery space is left in the center of the body. Control will be done by the ottantotto (an arduino -like board which I designed two weeks ago, specialized in controlling RC servo’s (I am anxiously awaiting the delivery)
I started out with a cardboard prototype (not functional at this time, just to check all sizes):

After this I decided to make a protoype out of acrylic plate:

As soon as the design is tested and proven to work, I will post the design files here.

I’m really enthusiastic about the reprap project. The whole Idea of having a printer that can print functioning parts, just on your desktop is .. well.. cool. The reprap is a machine that can replicate part of its own parts. However, to build one from scratch you get a certain ‘bootstrap’ problem.. Hence you have to start out with a ‘repstrap’. Or simpler said, build a 3d extruder/printer/milling machine from scratch so you can make the parts for a reprap machine or any other design.

This is the first post on this subject, the X-axis of the machine is more-or-less finished. Parts used are:

• M5 threaded rod
• stepper motor and bearings from 5 1/4” diskdrive
• MDF and screws
• two slider-bearings from a kitchen drawer

Normal ball-srews have a larger pitch, so the cart can travel faster. This cheap solution using normal screw end is probably going to be rather slow… Oh well.. you have to start somewhere.. I made this part in one evening in the lab with the Spullenmannen, after a toko on OpenFrameworks and ComputerVision.

The previously discussed LED matrices have been mounted on a perspex stand, and instead of the mublock controller I have used a normal Arduino Diecimila. Since the software was originally written for WinAVR using some of the AVRlib functions, I haven’t made a full functioning Arduino sketch yet. Bitmap images give the start configuration for the game-of-life simulation, so you can immediatly play with ‘gliders’ or ‘lsww’ (see wikipedia on Conway) The bitmaps should go in the ‘data’ directory with the processing sketch.

Here’s the processing sketch:conwayprint32. A ‘clean’ sketch for displaying just 32*32 monochrome bitmaps: bitmapprint. The arduino sources are here: arduinoleddisplay.

These sources do not work with the normal Arduino programming environment, since I haven’t figured out completely how to do timing interrupts etc. I have used WinAVR. The sources compile with Make All.. Make Program will program the sources normally. (don’t forget to set the correct COM port in the makefile)