Happy Birthday, and variations thereupon

Northackton is 3 years old this month.  The exact week can be derived from reading the first few posts in the archives, and/or by looking at flickr, but I won’t spoil it for you.  To celebrate, Andy had suggested an informal competition to produce devices that play the Happy Birthday tune.

A number of entries were made, and here they are for your enjoyment:
Andy’s recreation of our first attempt to play music bottles with servos.  He authentically captured our discovery that servos aren’t very good at this
 
Andy’s second entry was an Arduino piezoplayer:
  
Adrian made a xylophone using old pinball chime solenoids.  It only had three notes, but it played them really well!
 
Mine was another Arduino player, but with a mini speaker in a little box.  I don’t have any video of it yet, it’ll have to go up in a second post.
However the show was stolen by newcomers Mike and James who came for help making their ring modulator work.  Happily they’d got it almost entirely right, and some slight tweaking and a lot of soldering produced a very special song.
 

Bits of SDR

The hackspace is a bit quiet at the moment, we’re waiting for some room to set up our laser cutter.  NSME are kindly giving us some space and have even provided some fire extinguishers, optimistic that they are.  Hopefully by the beginning of April we will have space for it.

In the meantime, I did some tooling around with the RTL SDR dongle, the software support for which has come on marvellously, and after some fun following some guides on the ‘net, we were able to pick up the ADS-B location broadcasts of airplanes overhead – albeit in a very small range, due to the antenna in use that isn’t designed for 1.09GHz.
For the curious, I originally started with the rtl_adsb library that comes with rtlsdr these days (also worth investigating the rtl_tcp server if you want to leave your dongle in an RPi…).  This puts out the decoded broadcasts to an almost human-readable level.  I then installed the VirtualRadar software (which is cross platform) . . . which didn’t decode the messages at all (linked together via netcat).  It confirmed it received messages, and that they were not badly formatted, but couldn’t decode them either.
I then tried using this guide and used the gr-air-modes application instead.  The uhd_modes.py script it recommends has been replaced with rx_modes instead but the syntax is the same.  This wasn’t too painful for me as I already had gnuradio installed.  For those that don’t though, the latest in Ubuntu 12.10 is compatible with the osmocom extra sources.