Drawing Hilbert curves with an NXT Plotter

Drawing Hilbert curves with an NXT Plotter

In early September, Kevin built a plotter using NXT, using the design from the book “The Unofficial LEGO MINDSTORMS NXT 2.0 Inventor’s Guide” by David Perdue & Laurens Velk. It is an amazing book with lot of good ideas and designs. I was not content with the NXT 2.0 text and the graphic it printed … more

Shades of Grey

In CSS, when I need a shade of grey, I often use hex rgb like #cccccc, #eeeeee etc. (or in short form, #ccc, #eee) I posed myself a question today: If by using repeated hex notation, do we evenly divide the grey space from #000000 to #ffffff? What I found was very interesting. Let us … more


Just realized I did not post any blog entries this whole year, so let me rush! I was casually looking for properties of the number 2014 this morning, and stumbled on to this neat property: http://oeis.org/A083074 – n^3 – n^2 – n – 1. When I looked up for n, a pleasant surprise! It was … more

Christmas Tunes and Light Show with Arduino

I programmed 5 Christmas tunes in Arduino, and also made a synchronized light show with some special effects! It plays the following tunes in sequence after each key press: Jingle Bells The First Noel O Holy Night We Three Kings What Child is This Merry Christmas! Here is the source code if you are interested:  … more

NXT Virtual Piano – Fail!

NXT Virtual Piano - Fail!

Well, this was my plan – to create an extremely simple virtual piano with Lego Mindstorms, just by using the ultrasonic sensor in the manner below: To play the correct frequency for the detected key, I first tried a ladder if-then-else within the Mindstorms visual programming environment, and it absolutely tanked! For every if-then-else path, … more



I wanted to create a robot that can draw something on a paper. Searching for some inspirations, I found on YouTube, a variety of very amazing and cool implementations. Yet, they all drew on a horizontal plane, and were mechanically complex. I wanted something that I could mount on my son’s easel, and draw like … more