Aurora’s LEGO Robots

Building the perfect robot for the right job.

If you’re new to robotics, LEGO makes it easy to build robots.

Even if you think you’ve outgrown LEGOs, take a second look at the inventions below that I’ve created. Many scientists and engineers got their start building with LEGOs! My kids and I share many LEGO sets together, and my absolute favorite is the 1999 Lego Mindstorms set.

We still use it to build and program robots today! But don’t feel limited to this set, as it’s hard to find nowadays. Use this page as a source of inspiration for your own inventions. Although these are images and not videos, do you think you can still figure out how they move?

Tabletop Cleaner

A combination of the Ultimate Builder’s Set and my own creativeness and a differential light sensor (see below under “sensors”), this little guy can stay on a tabletop with right and left edge detectors, rear edge detector, and avoid obstacles with a left and right bump touch sensors, and can track a beam of light or find a light source using Michael Gasperi’s differential light detector.  Using six sensors mulit-plexed into three available input ports on one RCX, a little creative programming, and three motors (one for the brushes, two for the drive) makes for a cool project!

The Claw IV

One of the first things I’ve built from the Mindstorms box: I added pneumatics and a ball, and suddenly I have a 4-axis grabber arm with a pneumatic claw that picks up balls from one location and deposits them to the target every single time! I must add that if it were strictly open-loop program, it would miss after the second or third try, as it never quite comes back to the same spot. This MEGA CLAW uses four sensors, five motors (three for the three-axis movement, one to operate the pneumatics valve, one as a pump to keep the air tank stocked), one RCX, and one Scout (to handle the extra motor ports).  Sensors detect the mechanical limits of the arm.

I initially wanted to make a 5 or 6-axis arm, but decided to wait until I understood how to get these pieces to fit together more efficiently.

Max the Hexapod

I was so intrigued by the idea of a six-legged walker that I went right to the source – Flik by Nick Donaldson and Hexapod by JP Brown and made JP’s posted version of a single RCX Hexapod.  It worked wonderfully!  It took every last LEGO piece I owned to put Max together, as he’s a rather large robot – over 2 feet long, not including the whiskers.

Aft Articulation Point Forward Articulation Point

Killough Platform

This is a Killough drive system from Macs Robotics Page.  This platform can simultaneously rotate while driving forward.  Think of how an office chair’s wheel base rotates around while you push the chair across the

Same assembly three times make up the structure of this amazing robot platform.

Synchronous Drive Platform

This is a Synchro motor drive system also inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The coolness behind this system is the robots ability to turn its wheels in place without
turning the platform – hence this robot does not have a “front”, “rear”, “left”, or “right” – it goes in all directions!

Wheel assembly – each wheel is powered and can change orientation.

Top view – note that this robot was built upside-down!!

Tricycle Drive

Yet another Building Robots with LEGO Mindstorms inspired design.  I did not have an RCX free when I built this, so I plugged it into the Scout and made both motors go forward.  What was interesting about this was the vehicle initially went straight, then slowed and turned, then reversed direction in the turn, went backward, and began to turn again.  One motor controls the drive, and the other controls the front wheel’s orientation.  So when someone asks, “Can you build a car to go forward and reverse without reversing the motors?” you can say “Yes!”

Twelve-Legged Robot

This robot was inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The idea is to make a walker platform stable enough to turn tight corners while line-tracking.  The only improvement I would do next time is to couple the motors (independent motors – one per side – in above photo) so it does not have a gradual turn while it walks!


From Jin Sato’s book, The Master’s Technique, we created MIBO, a LEGO version of SONY’s AIBO – a robotic dog that can sit, shake (sort of), and shuffle along the floor.  He barks (more like a beep, really), and is lots of fun!!!  We’re adding non-LEGO parts, such as a wireless camera and sound sensor for further abilities for MIBO.  (Chasing ball and following a whistle?)  We’re really excited about MIBO and thank Jin Sato for all his hard work!


The SHRIMP is a high-mobility wheeled rover designed by the Autonomous Systems Lab in Lausanne, Switzerland.  This innovative rover is capable of climbing over objects 2.5 times its wheel diameter!


Whiz is a “whiz with sensors!” robot geared for a complex game of RoboTag.  This amazing robot is capable of exploring and reacting to its environment!  Whiz is loaded with a differential light sensor to seek and find
light, a sound sensor to detect and react to sharp sounds, a line-detecting sensor mounted on the front for staying on a tabletop or within a black-outlined rink, and it can avoid obstacles by knowing which bumper – front or back – is triggered.


Close-up views of the cool stuff:

Differential Light Sensor

Sound Sensor

Due to port limitations, I’ve plugged in a relay to switch between the sound and differential light sensor.  The following ports are connected:

Input 1 Touch Sensors (both)
Input 2 LEGO Light Sensor
Input 3 Differential Light Sensor and Sound Sensor
Out A Left Motor
Out B Relay and LEGO Lamps (optional)
Out C Right Motor

Front View(Two “eyeballs” are CdS light detectors in the differential light sensor)

Rear View (see the microphone?)

Top View (Blue box on left side is the relay)

Right Profile (Rear -> Front)

Left Profile (Front -> Rear)

Homebrew Sensors & Actuators

These sensors were adapted from Extreme Mindstorms: An Advanced Guide to Lego Mindstorms by Dave Baum, Michael Gasperi, Ralph Hempel and Luis Villa.  Many thanks to all these wonderful inventors for their genius!

This differential light sensor (as described in great detail in Michael Gasperi’s section of the book mentioned above) does a wonderful
job of being a “smart sensor”.  What would normally take 2 of your 3 sensor input ports to tell which way a light source is (to the left or right), this one tells you the difference and takes only 1 input port!  You don’t need the full capacity of the LM324N – if you have a 358 handy, use it.  The larger the CdS photocells, the
better it reacts.  This sensor is excellent for tracking a light source!!  Currently used on Whiz.

A sound sensor initially seemed like a silly idea – especially when Michael Gasperi pointed out that it turned your expensive LEGO robot
into a clapper.  But then, during a game of RoboTag, we realized that it might not be such a bad idea.  It would be handy to have
one robot beep and the other listen and search for it.  It worked pretty well for our application, and allowed us to use multiple robots
to search for different characteristics (light, sound, touch, temperature…).  Currently used on Whiz.

I just had to know what was inside the expensive little light sensor that comes with the RIS.  I was very excited when I found the schematic
online and went to work right away.  I am lucky enough to have a lot of parts on hand, and have noted some standard parts you can use if
you don’t have the oddball ones mentioned in the schematic.  Works great!!  (Not currently used on Whiz)

I figured, if the sensor above can see light, why not add in IR capabilities and find out if it can see the difference between white and
black?  Take out the phototransistor (the transistor in the schematic without a base) and insert an IR detector.  Add in the LED everyone’s
always taking out – but be sure it’s an IR or visible red LED (red LEDs often also emit in the IR range, and you can see if they are on).  If
you wrap the detector in electrical tape to shield it from side-lighting from the LED, it works more accurately.  It has a drop 15-20 (out of
100) between black and white, depending on your lighting conditions. Good enough for line-tracking!  (Not currently used on Whiz)

If you’re short on input ports, and you’ve got two touch sensors to wire to only one port, consider this:  wouldn’t it be nice if the
RCX read one value for one sensor, and a different value for the second sensor?  To make one sensor read differently than another when both
are plugged into the same input, you’ll need to make a special wire for the connection.  Solder in a 22k resistor at the end of one of the
wire leads just before it goes onto the electric plate, and your touch sensor will read about 50, whereas your straight connection (using the
black wires that came with your RIS set for connecting sensors) will read 100.  When you program, pretend it’s a light sensor reading two different values.  Currently used on Whiz.


10 Responses to “Aurora’s LEGO Robots”
  1. The original RCX firmware was on a CD-ROM. I am not sure if it’s available for download anywhere or if you can still purchase a disk. Have you contacted LEGO?

  2. jamallwh says:

    Do you remember how to download the firmware?

  3. The command to upload is nqc -firmware firm0332.lgo

    from here:

    Does this help?

  4. jamallwh says:

    Can You teach me how to download The rcx firmware?

  5. Aurora says:

    I wish I had taken a video of how I created these back then (I think it was about 20 years ago!) I am sorry I don’t have instructions to share with you… maybe you can figure out something from the photos?

  6. jamallwh says:

    can you please tell me how to make the 12 legged robot out of Legos

  7. Sure! You’ll need to start with the fundamentals if you’ve not had circuitry lessons, those are here:

    and then you can move on to our robotics lessons here:

  8. jamallwh says:

    Can you please tell me how to make the 12 legged robot with two motors?

  9. Aurora says:

    I think it was $200 back in 1999. I know Bricklink still has a couple left, and this is also where I ordered a bunch of extras, like motors and sensors and the extra RCX. You can use the current Mindstorms set that Lego sells now – these pictures are only meant for inspiration! 🙂

  10. Lynn Glasheen says:

    How much is it for the entire kit.

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