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Exotic timepieces of all stripes have always fascinated me, from water-powered clocks to the massive type that serves as an integral part of building architecture. Rolling ball clocks have also piqued my interest, hence this post about Philippe (“Philo”) Hurbain’s RCX-powered rolling ball clock, based on an original design by Bob Kojima.

Powered by a single RCX 1.0 (w/AC power) and equipped with a number of tiny LEGO balls (see below), this contraption can keep track of time thanks to some custom NQC programming and an elegantly-designed 8-bucket ball elevator. On his website Philo explains how he surmounted one challenge — an overly speedy RCX processor — with some custom NQC code:

The problem should have been very simple: each minute, start the elevator until a ball is detected by one sensor. Unfortunately, my first try over a several hours period showed me that my clock was fast, several seconds each hour! After eliminating all mechanical possibilities (two balls at a time, or an undetected ball), I concluded that my RCX itself was fast… To make sure, I finally put a frequency meter probe on RCX crystal, and indeed it oscillates at 16.03 MHz instead of 16.00 MHz. So I finally added some code to wait for 6.92 seconds each hour.

Check out Philo’s complete web page for more details on how he modified the design to overcome other challenges, along with some useful links and other info. (Source: LUGNET, Philohome : Images (c) Philippe Hurbain) – [Jeff James]

This entry was posted on Wednesday, August 16th, 2006 at 3:07 pm and is filed under Mindstorms (1.0-2.0), Mindstorms programming, RCX old school. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.