Another RCX-based balancer

I’m a sucker for interesting robots. Especially if they are built out of Legos. Everybody loves the Legway, but you have to admit that the concept is overly simplistic. The real challenge is building the system around the limited resources of Lego’s RCX.

Now meet another balancing robot courtesy of Maurits Kooiman on Lugnet. This one balances on one wheel and apparently uses two RCX bricks and four sensors along with three tires to maintain balance on the axis perpendicular to its unicycle. The robot balances on the main axis by directly powering the wheel. The axis perpendicular to its unicycle is balanced by the set of rotating tires. The fourth tire seems to be a freely swingy pendulum, but it may in fact be controlled by yet another motor. Check out the video!

Published on Mon, 13 Nov 2006 16:38

Nic_1: Sound following robot

There are a lot of LEGO Mindstorms robots out there, but I finally found the best. Nic_1 is a Johnny V impersonator that detects the direction of sound and follows it. Detection is accomplished by calculating the cross-correlation of two audio signals from the binaural sensor. The data is used to estimate the phase difference between the them. (Videos tracking Kelly Clarkson included!)

Nic_1: Johnny V impersonator

I can’t wait any longer for LEGO Mindstorms NXT in August. 32 bits, servos, and mics, oh my!

Published on Fri, 10 Feb 2006 15:01

DIY Lie detectors

Makezine recently posted a diy lie detector kit that uses your skin resistance (aka sweat) to detect a lie. The kit is well explained and consists of two probes you place on your palm with a red/green led readout.

Multimeter based feedback

This is all well and good, but sometimes a little more feedback is a bit more intuitive. We are trying to learn here.

Some time ago, Jason Bradbury created his own lie detector using only a resistor, a transistor, an led, and a multimeter. The led lights up if you are lying, but the multimeter provides more precise feedback of the skin’s resistance.

If you are really desperate, you can just clip the leads of your multimeter straight to your subjects palm. The ‘scary’ device may cause them to sweat and ruin the experiment, though. Just don’t tell your girlfriend you will shock her if she does not love you.

Finger straps and the LEGO RCX

The galvanic skin response sensor uses a LEGO RCX brick to detect lies and also has numeric feedback. The finger straps are the best part of this project. Your subject will know you mean business when you clip these puppies to your multimeter.

Galvanic skin response finger straps

Published on Fri, 20 Jan 2006 14:10

Mechanical logic gates

A few people have designed boolean logic devices using LEGO pneumatics… I had suspected that there would be a large number of logic devices using mechanic principals, but a search for mechanical logic devices didn’t get many hits.

He decided to take matters into his own hands and design mechanical LEGO logic gates. A clockwise rotation represents a binary “one” while a counter-clockwise rotation represents a binary “zero.” The AND gate seems to require less pieces than a NAND gate, contrary to transistor design.

LEGO Mechanical Logical AND Gate

Unfortunately, he failed to implement an XOR gate. I wonder if it would require a more complex mechanical design (contrary to its simple transistor layout.) Kudos to the first person who implements a 16-bit binary adder with a Manchester carry chain using LEGO! VLSI is not my strong point.[…]

Published on Sat, 14 Jan 2006 02:17

Mindstorms NXT poised for hacking

I am a huge fan of the original LEGO® Minstorms™. The platform seems to be dead lately, in spite of the FIRST LEGO® League and ongoing hacks of the RCX. Personally, building custom sensors and hacking on BrickOS were the only things that attracted me. The standard components and programming enviroment were better suited for children, but too complex and boring to keep their attention.

However, LEGO® Mindstorms™ NXT is poised change everything and bring the joy of hacking to less experienced LEGO® users through 3rd party support! Everything has been revamped and a team of four major Mindstorms™ community members contributed to the new design. NXT corrects several major downfalls and encourages hacking.

Mindstorms™ NXT - AlphaRex[…]

Published on Thu, 05 Jan 2006 18:18

Square Lego wheels

The Troy, NY company that invented a mechanism for powering a vehicle with square wheels has been all over the web lately. Their idea is obvious, but ingenious. The square wheels are turned by a rotating mass mounted atop the vehicle. Everything is angled precisely causing each wheel to successively roll flat as the mass rotates around the vehicle.

Several LEGO maniacs decided to try this on their own. (Video included in the first link.) The results are simple and successful.

Square wheeled LEGO vehicle #1

Philo’s Solution (with video)

Square wheeled LEGO vehicle #2

Alexander’s Solution[…]

Published on Sun, 01 Jan 2006 03:39

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