July 30, 2007

Log clock: technotrash version

While cleaning my room and throwing stuff out in general, I came across an old cdrom and laptop HDD. After taking them apart for salvage and throwing the rest away, it hit up on me to make a clock out of them!

Since I already had my log clock code written up, I just used that. The lens assembly moves up and down to tell the time, with intervals marked out by the bits and pieces I kept while taking these things apart. There is a little blinkenlight on the hdd portion to indicate activity (blinks every 2 seconds). The lens assembly "rewinds" itself back up to the top at the end of each 12hr cycle, during which the main rotor will spin.

Now for some pictures:

Building this taught me a few things, including the finer points of building a NPN only H-Bridge, the intricacies involved when dealing with mechanical systems and especially motors. Of note is the delicate movement of the lens assembly, which travels a different distance each interval depending on how long it has been since it was last moved. My initial method of determining where to stick the indicator involved holding down the increment button to step through all the intervals, which leads to long "travel". In practice, the minimum delay between movements is 60 minutes. I only realised this half way through, so now the first half of the interval markers are a bit off - but the whole thing wasn't entirely accurate anyway :P

Another "problem" with this design is that it requires a constant power source, which meant batteries can't be used. Batteries decrease in voltage/current considerably over the course of their life time, and with no voltage regulator, it means varied response from the motors, which further renders the clock even more inaccurate. I didn't take this into account when building it, so now I am short 1 plug pack :-)

Now to polish the front face to get rid of the residue of using too much super glue, and it will be finished :-)