Homebrew PCBs

roger lucas wrote:
> For those interested, the vibrating electrode is
> driven by the solenoid arrangement in an aquarium
> aeration pump. Simple, cheap and very effective.
> However, production item may have to be a lighter
> design to increase the oscillation frequency.

Isn't the frequency of an aquarium pump determined by the power line 
frequency?  In the designs I've seen its just a coil driven from the 
power line pushing a magnet connected to a lever that moves a diaphragm 
attached to a cavity with holes covered by small rubber flap valves.

Dave K