Let's Make Robots!

Robot Wall Racers

Finds the hidden racing track in every room.. and races it!

This is updated, reason is here


A video in better quality than YouTube & Google is here

How to make Robot Wall Racers yourself, see here

The car-chase was made by holding a camera on a stick, chasing the cars around. Some clips where made by placing the camera on a record-player. All editing was done in the standard "free" program that comes with a Mac, called iMovie. It is a nice program for light editing.. but phew, it was pushed to make this

The second video shows some work with the skid-turning. It also shows improved handling in general.

Notice how it sometimes mis-judges when the wall is not 90 degrees, but has bumps. But also how it handles getting out again :D (Me proud, love this, think it is cool, it drives so much better than what I can do with remote myself)

Of course I could just give it some more space to turn in the code, to drive more "safe", but I kind of like it to be tight :) And notice hw it never bumps into anything else - the polystyrene-blocks would fly right off if it hit them.

I have added an extra battery for more power.


Your home is a racing track, you just do not know it.

Look at your floor where it meets a wall.

Between 30 and 70 cm from that goes an imaginary path, following along the wall.

That is the racing track!

Where the wall meets another wall, or there is an obstacle, the track follows in a smooth path, always 30-70 cm away, on the floor.

The track returns to where you started, you see! :)

It is a full racing track:

You can time how long time it takes for a little robo-car to take one round. You can then try to improve the code, and time it again.


If you make the car like this:

One sensor (Could also be infra-red or whatever) looks ahead, another looks to the right. Then code could be something like this:


If something in front, turn left, go to main.

If something closer than 30 cm to the right, turn left, go to main.

if nothing in front and something closer than 70 cm to the right, drive ahead, go to main.

If nothing to the right closer than 70 cm, turn right, go to main.


A car is racing your home!

It can be timed how long before passing by the same line again and again.

But a single car is just test-labs, no?


Now take 2 cars with the excact same setup as above, let's say a red car & a blue car. Now it get's interesting!

If red car is behind blue car, what does it do?

Well.. Something (blue car) is in front, so we turn left to take over.. until nothing is on the right, so we pull back.. That is trying to take over!

At a point the blue car is turning left because there is something in front.

Then the red car will have the inner track..


What is actually going on, is that one car is behind, but is "strugeling" to take over.. when it is in front, the other will fight to get ahead.. and we have a full race :D

You can take Red & Blue and place them next to each other, next to the wall; They will both drive full speed ahead, until a turn, where the inner car will have advantage. But then..

Wall Racers are born, ladies and gentlemen.. I had these 2 cheap RC cars with crap maneuvering abilities, and thought of what I could do with them. Crap - but still; They sort of drive like cars - not like differential steered robots.

It has ben quite simple, have experimented with AZ8222's instead of motor drivers. And just a Picaxe on a standard board, simple and fast.

Of course, when turning angle is not enough to avoid obstacles, maneuvers with reverse and 3-point turns must be done. But this is why we have a microcontroller, and it is not spoiling the fun - on the contrary :)


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I would assume that as long as it has holes for sound to go in and out it should be ok. The more you block it the more of a chance that you will get a bad reading. If you put something in front I would try to make sure it is as close as possible to the sensor and that the holes line up if possible. I would just drill two holes and have the sensor peek through.

Realy like the fact that you have taken radiocontrolled cars and made them childproof, radiocontrolled cars that doesn't drive into thing that's definetly something I think a lot of parents would like and that way they also last longer

Have you thought about hidding the SRF05 sensors indside the car, can't quite come up with a way to hide ultrasonic sensors inside the cars, I can only think of a way to do it with infrared sensors.

The SRF's could just be better placed inside the cars.. Only the cars I made are completely filled up on the inside :)


I was impressed with your racers, made me want to do my own now :) i was thinking about how close you could get them to the wall,have you tryed putting proportoinal responce into the code, something like


x=distance from wall on right;

y=distance from wall infrount;


turn Z amount.

I made a wall follower once for university and the idea was it would always stay 3cm away from wall and follow it. i found the type of forumula above was fairly easy and produced good results,might make it more fluid.

 if you have something like excel or matlab you can even find the best turning curves etc.

 Anyways great project and i liked the videos alot.


Hum.. erh.. thanks.. hmm..

Well - to put it short; I think one thousand nerds out there have tried to make something like wall racers / Microcontroller on an old RC. But failed because they thought they could calculate the way out of things / predict etc like the robots they have experience from.

The thing is; These things (specially the cheap ones) steer like a numb fish, react like a drunk fish, and whip around like fish on speed in a heavy stream. It is NOT like a nice slow little robot. You cannot transmit formulas from "ordinary robots" that behave nice to these things, they will bang into the wall and act crazy if you try. It has to be formulas on how to steer a numb, drunk fish - on speed, in a heavy stream :)

But I will release both code and how-to's asap. I will release a very simple base-version that works (100% the one on the videos, and possibly more videos to come) - and then you can have all the fun in the world by trying different formulas - they take an afternoon to build, and are very cheap :)

Thanks again,


You evidently have most experience, so how exaclty DO you steer a drunk, numb fish on speed in a heavy stream? Is it anything like trying to steer a frightened sheep towards the edge of a cliff while wearing your wellington boots?
Walkthrough is comming - with code :)

very very nice,

good stuff always rise from simple ideas. 

Awesome, I love the idea, the implementation. gimme more :)

Oh man, these robots, like all of your robots, look so fun. One MORE idea I want to play with :) The speed, I think, is the big think that makes these appealing. My attempt at controlling an R/C car with a microcontroller didn't work very well, because it couldn't process the input from the sensor fast enough to react in time. But these can aparently react even when driving at full speed, and that makes them really fun :)