Instructables

Wallbots: Autonomous Magnetic Robots that Traverse Vertical Surfaces

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This Instructable will teach you how to create magnetic robots that traverse vertical surfaces. These robots can move on any metallic walls, including elevators, whiteboards, refrigerators or metal doors.



The robots are outfitted with several light sensors, allowing them to respond to simple user interactions. My implementation supports 3 robot 'personalities', which can be changed by covering the topmost light sensor:
Red robots move fast, going towards objects (such as human hands or other robots)
Green robots move slower, turning away from objects
Yellow robots move the slowest, and stop completely when motion or objects are detected

This instructable details my first prototype. In the future I plan to build in more complex, autonomous behaviors. I will use these robots to engage people in public spaces such as elevators or hallways. In doing so, I hope to facilitate creative interaction between people and technology in mundane, everyday settings.

Stacey Kuznetsov
stace@cmu.edu
Human Computer Interaction Institute
Carnegie Mellon University

for Making Things Interactive, Spring '09

*** UPDATE ***
I recently made another version of this project using continuous servo's from sparkfun and a custom-cut PCB. The new robot is much much sturdier:
 
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Step 1: Gather Materials

Picture of Gather Materials
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To make one robot, you will need:

2 servo motors http://www.rctoys.com/rc-toys-and-parts/DF-SRV-6G/RC-PARTS-DRAGANFLY-SERVOS.html?utm_source=googlebase_froogle&utm_medium=US&utm_term=DF-SRV-6G
4 light sensors http://www.goldmine-elec-products.com/prodinfo.asp?number=G14025
4 2.2 K resistors
4 10K resistors
1 100 ohm resistors
1 Arduino Mini http://www.arduino.cc/en/Main/ArduinoBoardMini
6 magnetic disks http://www.kjmagnetics.com/proddetail.asp?prod=R8201
1 RGB LED http://www.superbrightleds.com/pdfs/RGB-1WS.pdf
1 lightweight Battery http://www.sparkfun.com/commerce/product_info.php?products_id=731
Some hard wire (not easily bendable)
Electric Tape
Wire
Shrink Tubing
Cardboard or paper
Hot glue or epoxy

You will also need access to:
Soldering Iron
Hot glue gun (or epoxy)
Scissors
Wire Cutters
Exacto Knife
kalaquin1 year ago
Amazing I am going to build this soon
djatico692 years ago
just wanna ask if you have any programs on the part of arduino...
Mic1002 years ago
Very nice and good instructables for how to hack mini servo to
Thacks :)
I'm not great at electronics, but most of this makes sense and it looks awesome :)
BUT anyone know how I'd go about using a picaxe instead of arduino? Thanks muchly :)
Sovereignty3 years ago
It'd be nifty to have them clean yer windows; one on each side, like them aquarium magnets. Switch out the marker tail for a squeegie and Windex.
J-Five3 years ago
COOL!!!
Skyriam3 years ago
This is awesome! Absolutely loved the second version of the robots. How do you make them to follow a person/object? Thanks for your time!
Carnavislol3 years ago
Very nice I will be making this soon.
Thegame9953 years ago
Wow! This is incredible! Do you sell 1 of each one?
midnsun1833 years ago
you sir are a modern Mozart! BRAVO!
Default1173 years ago
It would be better if yellow robots would bite your hand instead :)
PS1185 years ago
These things are so cute! I think it's a travesty that this one wasn't "featured". BTW, How much does one cost? Also, since they travel on whiteboards, it could be fun to give them a marker "tail" so they make designs in their travels.
raykholo PS1183 years ago
I love the marker tail idea! That would be so cute. Cost wise: the servos he uses are $10 each. An arduino like his is in the range of $20. Add headers (the connectors), the leds and photocells, and shipping, and I would say that each one cost him around $70. I could make it quite a bit cheaper though, just by using a different microcontroller and buying cheaper servos in bulk.
the opposite would be fun too - add an eraser and these would be like the Roomba robotic vacuums, but for the whiteboard. Turn them on when you leave at night and come in to a clean board in the morning!
lol. Wow this is a fun thread to be participating in! Given the processing power of arduino, I would get some proximity sensors and maybe a compass sensor, so that this thing can go up until it senses the edge, turn to the right and go for a bit, then go down and do the next row, and so on. Only thing is that you would need to install a ledge at the top much like the one on the bottom that holds the markers.
staceyk (author)  raykholo3 years ago
I recently made another version of this using continuous servo's from sparkfun (http://www.sparkfun.com/commerce/product_info.php?products_id=9347 - $13)

Some pictures here

And a demo video

I
 used a custom-cut PCP, which cost me $89 for about 20ish boards?
So I think the price per one is
$26 for servos
$5 magnets
$20 arduino
$5 for the custom cut board
$2-3 for wires, LED's, resistors, etc

So about $60 just for the robot itself. Then, the price goes up depending on what sensors/lights/etc you put on it. Photocells are less than a dollar, so  is a hall effect sensor- which you can use to detect when the robot is about to climb off a magnetic surface.


perfect timing, posting that video. I must say, using the hall effect sensor as you have just described is pretty genius. I had not thought of that. I am definitely going to be making something like this bot in the future, as soon as I can clear some time to do so. I would make the pcbs by hand, and I use the raw atemega chip + oscillator right on the pcb to save money. Not much to say for the servos. Also helps that I have a fully stocked workshop for everything else.
staceyk (author)  raykholo3 years ago
how do you print your own pcb?
There are some great instructables here for home etching pcbs. I'm working on getting access to a CNC mill (also some great instructables here for that), but right now I use the toner transfer method and chemicals.
Cynar raykholo3 years ago
http://www.dealextreme.com/details.dx/sku.35764 Good little miniture servo that might be helpful
pocketspy PS1183 years ago
I like the marker idea. If you could use a smart board like Mimeo, that my ex, an art teacher uses, you could have them create art and 'save' it to your computer.
Cynar3 years ago
If you added a larger flat magnet in the middle of the robot it would give you a bit more weight to play with(just need to be careful of slippage). Good show though :-)
louisr905 years ago
how exactly would u upload the code the the control circuit and is there anyway for u to make a "kit" that other people could buy
staceyk (author)  louisr903 years ago
Yea i have a pcb, and bunch of extra boards i printed back in the day. it's pretty easy to put together
rlmagidson4 years ago
I've read in many projects about the "how" of hacking servos, but I don't really get the "why." Why is it better to hack a servo than just buy a (cheaper) motor that already allows for full rotation?
Thanks for taking the time to educate me.
- Russ
Servos are an easier alternative to using dc motors such as hobby or gear motors. They feature a built in gearbox and drive circuitry. Say a servo costs 10 bucks. If you get a hobby motor for $1 , you still need gears and drive circuitry. The common L293D dual motor drive chip (aka dual half bridge) costs about 5 bucks. Not to mention this requires more pins of your microcontroller (like arduino) vs. a servo only requiring one. A gear motor (with a built in gear box) will typically cost more than a servo itself. So... servos are quick, cheap(er), and are generally more convenient. In a project like this, there's no space to build 2 gearboxes with about a 120:1 gear ratio each. It also leaves a lot less room for error. I can't tell you how many robots I've built where the fatal error was an ever so tiny flaw in the gear train.
nak raykholo3 years ago
yep
Becouse it has got already build in drive transfer and you only mount wheels when you hack servo.
Munchys3 years ago
They look like moving led stop/street lights
AndyGadget5 years ago
It would be fascinating to have a LED at the back of each robot and give them an occasional light homing behaviour. You could than have a 'crocodile' of magnetic minibots.
So now we can move this project into swarm robotics with infrared leds and recievers as the primary form of communication.
marc.cryan3 years ago
Well done!
kinomix3 years ago
I think its awesome
killerdark3 years ago
Well done!
crossfire3 years ago
I love it! Can you make a kit for it?
noik4 years ago
skills
kcls4 years ago
Cool!
you should enter this into the arduino contest
robot7975 years ago
do you sell them i wanna buy 2 of them
magicpocket5 years ago
Beauty
Bongmaster5 years ago
what changes would need to be made if u were to use LEDs for the light sensors? (due to me only having one LDR). i understand the LED wouldnt be a very good light sensor but it can be one aparenty :)
You can't use an LED in place of an LDR, an LED only emits light, it cannot detect it.
actually it can. even tho its not made to do so. its prolly not that good at it tho, but they have been used in applications like LED tables that react to movement, the LEDs that are used as the sensors are used in between the ones that give light. check the arduino site, there are examples.
DemonDomen5 years ago
You should use a board to mount the electronics. You will use less wire, it will be more robust and possibly take up less space.
It's fine for a prototype, but yeah, a custom PCB would be most excellent.
Bongmaster5 years ago
kool looks like the kind of code i need for my R2 :3