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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Here I am again..... My R/C based model car robot is being marketed by Ten80 Education. The kit is down to aproximately $110. The target students are in middle school - seventh and eighth grades - ages 12 to 14. How do we help young folks conceptualize the microprocessor domain? -- Particularly without electronics like an oscilloscope? Please help me think of 'real world' examples like one demonstrating a millionth of a second and/or a machine driven my a megahertz clock.

Here's a short list

An Input - An Output - A pin
A signal -- a Digital signal -- an Analog signal
A microsecond - A millisecond
A pulse - The pulse width - pulse frequency
Ground (Gnd) - Operating voltage (Vcc) - A voltage regulator
Noise - DC motor - Electro Magnetic Force (emf) - Back emf
Resistance - A resister
microprocessor architecture terms
sonar - speed of sound


Would the SRF04 work for this project because it is much cheaper than the SRF05( 3x less on ebay). Would the connection and code be different? I am back after 3 years of absent so I want to give the wall racer a second attempt. Thanks

"The SRF05 is an evolutionary step from the SRF04, and has been designed to increase flexibility, increase range, and to reduce costs still further.  As such, the SRF05 is fully  compatible with the SRF04.  Range is increased from 3 meters to 4 meters."

I have had very good luck with the SRF05's but they are the most expensive part of this project.  Give the SRF04's a shot if you like and report to the forum how they work.



oh my mistake. the one on ebay is not the SRF04 but it was the  

Arduino Ultrasonic module HC-SR04 distance sensor. Would this still work?




I know of a person who made a wall racer using Arduino.   The sonar distance sensor he used (it might not have been this HCSR04 at all) gave him inconsistent information.  I do not know why.   There could have been a number of reasons for his problem. 



omg omg its sooo cooooooool i wan to make 1 too!!!!!!!!!!

hupssssssss it's now

I've deleted that line 128 and it works...thanks.

Cool. As for your other question, if you post your work in progress it will be much easier to help you; More info means better answers :)

Looking forward to see your project!! Are you making one or two?

I've made my first robot and you can see it on my avantar icon. I wanted to see if I could make it work and it does but it's very basic for my first one.I will post it. The racer would be just an idea because I have a 4x4 R/C without the transmitter. Also something on tracks would be great as a futur project too....so I'm on LMR everyday reading and watching other's projects and I'm learning with you people. Thanks again this is a great discover for me.