LOUD BIKE SIREN

Description: Utilizes a 5558 dual operational amplifier and four general-purpose NPN transistors to generate a triangle wave. This wave can be distorted using a 10k symmetry control, allowing for either a fast or slow rise time for the sawtooth waveform applied as base bias to an astable multivibrator formed by transistors Q1 and Q2. The circuit operates with a reasonably low drain current when powered by a 9-V radio battery. The repetition rate can be adjusted from a long wail to a rapid warble, and the output volume can be varied from soft to loud.

The circuit design leverages the 5558 dual op-amp to create a stable triangle wave generator. The triangle wave output is essential for generating the desired sound effects in the siren application. The symmetry control, a 10k potentiometer, plays a crucial role in adjusting the rise and fall times of the triangle wave, thereby influencing the timbre and character of the output sound. This feature allows for customization of the siren's tone, making it more versatile for various applications.

The output from the triangle wave generator is fed into an astable multivibrator configuration formed by two NPN transistors, Q1 and Q2. This configuration allows the circuit to oscillate, producing a square wave that can be modulated into different sound patterns. The choice of general-purpose NPN transistors ensures that the circuit can be easily assembled and maintained, as these components are widely available.

Powering the circuit with a 9-V radio battery ensures that it remains portable and suitable for applications such as bicycle alarms. The low drain current is advantageous, prolonging battery life and enhancing the practicality of the design. The repetition rate of the sound output can be adjusted, allowing users to switch between a long wailing sound for alerts and a rapid warble for attention-grabbing effects.

Volume control is another critical aspect of this circuit, enabling the user to adjust the loudness from a soft warning to a significantly louder alarm. This feature is particularly useful in different environments, where the ambient noise levels may vary.

Construction details provided in the original article recommend using a removable mounting system for the circuit, especially when installed on bicycles, to prevent theft. This practical consideration enhances the usability of the electronic siren in real-world scenarios, making it a valuable addition for safety and security applications.Uses 5558 dual opamp and four general-purpose NPN transistors to generate triangle wave that can be distorted by 10k symmetry control to give either fast or slow rise for sawtooth applied as base bias to astable MVBR Q1-Q2. Drain is reasonably low with 9-V radio battery, Repetition rate can be varied from long wail to rapid warble, and volume changed from soft to annoying.

Article gives construction details, and recommends use of removable mounting on bike to avoid theft.-R. Megirian, Simple Electronic Siren, 73 Magazine, Oct.1977.p176-177.