Bugler
Yes, it's loud.
Overview
In a Scout troop, bugle calls are used to communicate messages to a large number of people over a large area. Unfortunately, not every troop has a scout which can play the bugle.
Enter the Bugler (affectionately called "robot" by the scouts).
History
In 2005 I cobbled the first prototype (Hydra - because it has several horns) out of an electrical box, a few Valcom paging horns my Dad had laying around, and part of a wrecked wagon.
The Bugler was a huge hit and the scouts loved it.
In 2006 I was commissioned by Dr. Dave Schimmel to build two additional Buglers for the Atlanta Area Council Green Bar Leadership Training Course.
In 2007 the buglers were serviced and the charging circuitry was overhauled. They have been in use since 2006. They have weathered storms, been left out overnight and abused by countless teenage boys for the last three years. They are still loud.
Design
The design is centered around the horn, a Valcom V-1038, a 30 Watt one way paging horn. The V-1038 requires 48V at 1A. Obviously, it had to be battery powered.
For cost and charging reasons, sealed lead acid batteries were selected. Unfortunately, of the SLAs I had only two 12V cells fit into the selected enclosure. To obtain the required 48VDC for the paging horn, I designed a switching DC-DC converter to generate 48VDC from 24VDC.