Friday, 2 October 2015

Rainwire Prototype - Piezo Contact Mics

Assorted pictures of the first set of piezo contact mics I've custom built for the Rainwire Prototype in January 2015. The green piezoelectric bimorph element converts mechanical vibration into an electrical signal (RS Part Number 285-784).





The first step for the piezo contact mics is cutting and forming an audio cable, and then soldering on the bimorphs. The solder connections are then folded back over the cable and encased in gaffa tape. The bimorph connection wires are almost hair thin, so this process is extremely delicate...







The piezo element is first attached to the Rainwire Prototype by double sided tape. Note how the pickups are located at the same point on the wire, roughly 90 degrees apart on the top and the side.



For an overview and photostream of earlier wire pickups I've built please see my Contact Mic Workshop page at The Wired Lab, which so far have all been been positioned at different lengths along the wire. These two most recent Soundcloud example recordings were mixed using a Mid-Side decoding matrix, rather than using Left Right panning :




 


A waterproof sealant is used such as Selleys All Clear Multipurpose Co-Polymer, commonly used for bathrooms and roofs. A future experiment is planned that will use Sugru as a waterproof sealant. Note the cable tie holding the audio lead to the wire, this is important while the sealant sets, but is removed later.