Picture of The Carpet Crawler - A BEAM Robot.
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The Carpet Crawler is a small robot which will shuffle its way across your floor.  Watch the video, and you will see how it got its name (that, and I'm an old prog rock fan at heart!). 

BEAM stands for Biology, Electronics, Aesthetics, Mechanics, and is a school of robot design working on the KISS philosophy - I prefer the "Keep It Sweet and Simple" definition.   Google for 'beam robotics' and you'll find a veritable plethora of sites.

The 'brain' of this robot is a latching relay, the sensors are a pair of microswitches and the 'muscle' is a modified servo-motor. Energy comes from 2 x AAA batteries.  A pair of LEDs brighten things up a bit.

The original video was blocked almost immediately (in the US) by the copyright stazi, so here it is without the music. 
Look HERE to hear the eponymous track (but no Peter Gabriel on this one).


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Step 1: Tools and Materials

Picture of Tools and Materials
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Almost no special tools required - You will just need standard electronics workbench tools.  However, you will need a Very Small crosspoint screwdriver to open the servo.

Brass strip - 1/32" x 1/4" x 8"
Plain stripboard
2 offcuts of copper strip stripboard
M2 (2mm) nuts and bolts

Micro RC servo (7.5g) with horns and screws.
DPCO latching 3 Volt relay - I got mine from Farnell (9899600)
(They no longer do PCB mounting. This is the SMD version - smaller)
2 x miniature microswitches.  Mine came out of a couple of CDROM drives
2 x LEDs - I used red ones.  (Blue or white may not work in this application)
1 x 100R resistor (Use 47R if using yellow or green LEDs)
2 x AAA battery holder and batteries
Thin link wire
In the UK we use both Imperial and metric measures.  Personally, I tend to think Imperial but measure metric.  As a quick reference,  3mm is 1/8"   25mm is 1"   305mm = 1'.

danmcclain3 years ago
Very Cool!
Robot Lover3 years ago
Lots of clicking I would imagine with the relay and the switches. Cool instructable!
Very clever.
it is like a flip flop circuit mate!!!
tzq33tdq4 years ago
can it turn? this is an awesome robot!!!
AndyGadget (author)  tzq33tdq4 years ago
Nope - Forward only.
To turn, you'd need to limit the travel of the servo arm on one or the other side, which would need more complicated mechanics and electrics.
The aim of this was simplicity, although a much larger steering one shuffling around the garden would be an interesting idea.
If i made to and joined them together with a servo would it turn?
Unit0424 years ago
Interesting robot. I wonder if the relay could be omitted in favor of a custom made switch that performed the same function as the microswitches and realys put together.... Anyway, the relay is Double Pole Double Throw (DPDT). I think 'change-over' might be the archaic term from the days of relay-operated telephone system(?)
AndyGadget (author)  Unit0424 years ago
You could do it with a simple DPDT switch, but the mechanics would be more intricate and it would need to be a very light operation switch.  The momentum of the system would have to carry the switch beyond the 'break' position to make the other contacts.  A toggle-type switch would work but the force required to operate it would be higher.  It would be easier on a larger Crawler.
Regarding the DPCO - I'm pretty archaic myself and we used to use DPDT and DPCO interchangably, but you're right, DPDT is current and fits in with the naming scheme for other types.
By custom-made, I was referring to home-made, ie taking some stiff copper wire/paperclips, a square inch of cardboard(plus or minus a bit), and a tiny, weak spring (easy to get from dead printers, VCRs etc.), and a bit of patience. If you had enough patience, the homemade DPDT might work... although it would take a bit of ingenuity to make sure the problem you mentioned does not occur.
Dagnabbit, now I've got to go try it. My sense of curiosity won't leave me alone.... ;)
AndyGadget (author)  Unit0424 years ago
Hmmm.... That's a thought. I don't think you'd even need the spring if you used a slide type arrangement with drawing pins (thumbtack) contacts and foil to make the connection. I wouldn't trust my life to it though #;¬)
D5quar34 years ago
 Cam i get the latching relay on an U.S. site
AndyGadget (author)  D5quar34 years ago
Yep, THIS is the same part from the U.S. Farnell.
MoritzB4 years ago
Wow very clever circut, also the face of it looks great!
sci4me4 years ago
CUTE!! and awesome 5/5 =]
winterfresh5 years ago
 Sorry to rain on your instructable, but your video seems to have been blocked. Still looks cool though!

Keep Instuctableing!
AndyGadget (author)  winterfresh5 years ago
Rats!  I had the original song up on YouTube and would take it down if the copyright stazi objected, but it looks like there's a fingerprinting mechanism going on and it was blocked within an hour of going up - I'd gone to bed.

I'll repost the video later, but it won't be the original tune.
Well, the video is now up and, -Er, crawling. Still looking awesome! Maybe you could slap an Arduino onto one of these and teach it obstacle avoidance?

Scooch, scooch, scooch...
AndyGadget (author)  winterfresh5 years ago
Steering on this is rather limited - It only knows about 'forward'.
Another project, Techno-Gecko, is at the early design stage and this will have a PicAxe brain, directional control and sensors.  Big on design - Small in size.

AndyGadget (author)  winterfresh5 years ago
Can you see the vid now?
Music (of a sort) coming later.

(Your arduino head and my crawler could be brothers . . . Scary!)
Is that lambswool under its naked copper feet?

Wish I coulda seen the Lamb live, but being two years old at the time, I might not have fully appreciated it.

How about building a two motor version with radio control, so that the carpet crawler can heed its caller?
I thought about putting a few direct references in the text but I decided it would pass wayyyy to many people by.  (Small 2 servo walker in the design stage at the moment.  May be a while though.)
Oh well, if people don't get it, they'll just carry on as if nothing were there.
frollard5 years ago
I really look forward to seeing it move - looks really cool :D
Excellent 'ible!  The blinking LED eyes are a nice touch.

Can't wait to see the video.