August/September 2001 Issue #84

Solar-Powered Glass Armonica

William Wilde Zeitler


Ben Franklin (1706-1790) was considered one of the world's foremost experts on electricity in his day, and is known for many inventions. What isn't as well known is that Franklin's favorite invention was a musical instrument.


He called it the "glass armonica" after the Italian word for "harmony." It works on the wet finger around the wine glass principle. Franklin's idea was to nest a set of wine glasses inside of each other, one for each note, all mounted on a rotating spindle. Then you could play it with wet fingers, almost like a piano.


Otherworldly Sound

The instrument became very popular in the late 18th century — even Mozart and Beethoven wrote music for it. But around 1810, they decided that its otherworldly sound would wake up the ghosts, so it was banned. It's been on the Endangered Musical Instrument List ever since. For sound and video samples, and much more history, see my Web site.


I've been a musician since I was five, I'm a classically trained pianist, and I have a degree from the California Institute of the Arts in harpsichord. One day I tripped over a CD of "music by Mozart for the glass armonica." Having no idea what a glass armonica was, I took it home, and that was it. I had to play this! I found that Finkenbeiner Inc. was blowing the glasses again, and off I went. I know of only a dozen performers in the world. I do about 75 performances a year, and have three CDs, with number four due out this summer.


William Zeitler plays a solar sonata.

Not an Energy Hog

Franklin made his spindle rotate with a foot treadle. The main reason I opted for a motor instead of a foot treadle is that I can play much better standing than sitting. The 1/28 horsepower motor that turns the spindle draws a whopping 16 watts (measured at the wall). But when I play outdoors at weddings or festivals, I often don't have access to an AC outlet.

The instrument is already set up to use 110 VAC, so the simplest thing to do was to get an inverter and a deep-cycle battery. The smallest inverter I could find at the local RV supply was 75 watts. With the smallest battery available at Costco (90 amp-hours), I've run continuously for two-to-three days without a recharge (we also run a cash register with the same battery/inverter setup).

Mobile Solar Music

But I was concerned that I wouldn't have enough juice to make it through longer festivals, so I got a solar-electric (PV) panel to add to the system. The panel is a Solarex MSX-30 Lite, rated at 30 watts. It's a tough, bendable panel, which is perfect for taking on the road. At 24.4 by 19.6 by 0.6 inches (62 x 50 x 1.5 cm), it's still easy to find space for it in the truck (along with everything else one needs for a festival).


The solar panel is only connected when the battery is under load, so I don't have to worry about overcharging the battery. I hook the solar panel up to the battery in parallel with the load, with no charge controller. I wired a diode in series with the solar panel to prevent discharge through the PV when the sun goes behind a cloud.


I suppose I could get a larger battery, or find another way to run my instrument. But there's just something right about a solar-powered glass armonica. I think Ben Franklin would approve!