LadyBugBot

By isotope
@ Sun, 2009-11-22 19:53

• Actuators / output devices: Two servos modified for continuous rotation
• Control method: autonomous
• CPU: picaxe 08M
• Power source: 3 x AAA
• Programming language: Picaxe basic
• Sensors / input devices: Tilt sensor, bumper switch
• Target environment: Fridge door

Meet my robotic fridge magnet! :)

Once upon a time I was getting into my fridge for another bottle of beer, and after closing the door, my eyes stopped at little funny ladybug magnet... And I thought: "Hmmm... Why don't I build slightly bigger one, intelligent, robotic fridge magnet? :)"

In a day or two I already had a rough design in my head and started to collect parts. Controller: Picaxe 08m (this was my first time with it, and I'm pretty happy with it! ) with CHI040 board which I found fantastically convenient for variety of purposes as well. Base: defective CD (I had couple of). Locomotion: With 08m I had no luxury of dedicating 4 pins to motor driver, so, continious rotation micro servos from DAGU cuts pins count by 2, leaving space for bumper switch, tilt sensor and piezo speaker. I went to construction store and bought a bunch of furniture magnets. One of medicine dropper parts magically had perfect size for my tires. Now, the body... Hmmm... first I was thinking of some plastic ball cut in two hemispheres, but then I came up with papier-mâché. After I tryed it out, it was so cool, so I decided to write a walkthrough.

Below is the interrior view of LBB.

I had to hot glue 10 of my magnets to CD to have good enough magnetic force. By the way, My dead CD was LightScribe one, so I did not hesitate burning some stuff on it :)

The power switch fitted just fine in the CD hole. Below is picture of my board which is glued upon 3xAAA batteries taped to each other (initially I used 3xAA and battery holder, but this setup could not fight gravity :) ) which glued to servos which are in turn glued to CD base. You can see A tilt switch soldered onto board facing up. I use it to roughly determine if LadyBugBot facing up or down and use it in subroutine which makes LBB turn until facing upwards.

Wheels and mecano parts I used to screw body onto chassis:

Little piezo speaker:

And at last, my home brew bumper switch which is actually not only bumper switch, but cavity sensor as well. Basically it consists of 2 little levers glued to 2 springs which are centered between 2 contacts. If lever goes to cavity or bumps against something - spring completes switch circuit.  It took me long time to tune it to work properly.

Now, the behaivour. LBB basically roams around my fridge door and avoids cavities ie. door edges. Randomly LadyBugBot does some other actions:

• stops for 10 seconds and produces creepy sound
• turns left
• turns right
• positions itself upwards