Ramsey Electronics Electronic Dripping Faucet manual Introduction, EDF1 Circuit Description

INTRODUCTION

Have you ever had a project that you needed an alarm or alert signal for, but you were tired of the same old “beep beep”? Have you ever made an annoyance alarm to surprise that special someone, but the sound just wasn’t irritating enough? Well, help has arrived! The Ramsey EDF1 will provide you with a small, easy-to-mount noisemaking solution to fill all your unique auditory needs. All you need to do is connect a small 8 ohm speaker and off you go!

EDF1 CIRCUIT DESCRIPTION

This is a fairly simple circuit, and pretty easy to follow even for a beginning kit builder. The kit is built around a one-transistor oscillator made with Q1. This oscillator is underdamped and is “struck” into oscillation by briefly raising the voltage between R10 and R5. After the voltage between R10 and R5 returns to normal, the oscillation dies out, as shown in the picture.

The effect is an exponentially decaying sine wave. An NE555 timer provides the “striker” that gets the oscillator going. Every second or so the NE555 outputs a pulse that appears at the junction of R10 and R5. Then Q1 outputs the waveform above which is fed to an audio amplifier. The result is an output that sounds like a faucet drip or sometimes maybe a guitar string pluck.

EDF1• 4