Circuito original em: www.mitedu.freeserve.co.uk/circuits
Circuit: Graham Maynard
Text: Andy Collinson
Notes:
Repell those repugnent insects
from your Garden this Summer with this insect repellant circuit. Designed by
Graham Maynard the circuitry consists of a phase locked loop (CMOS 4047) wired
as a 22KHz oscillator. The output is amplified by a pair of complimentary output
transistors and drives a Motorola 3.25 inch Piezo. Current drain is around 120mA
so an external power supply is recommended.
The piezo used was a standard
85mm square Motorola Horn, Maplin part number WF09K or WF55K. These
are rated +/-3dB to 28kHz.