Circuit diagram

The circuit was designed to create an electronic siren to provide a scheme for producing an alert sound in emergency cases or any circumstances that requires its usage.

• 4011 – a quad 2-input NAND gate integrated circuit, generally characterized by small fluctuation in voltage supply, very high impedance, outputs that can sink and source, one output can drive up to 50 inputs, high speed gate propagation time, high frequency, and low power consumption.
• 4066 – a digitally controlled quad analog switch utilizing advanced silicon-gate CMOS technology with features such as individual switch controls, matched switch characteristics, pin and function compatibility, low quiescent current, low ON resistance, wide analog input voltage range, and 15 ns typical switch enable time.
• 4046 – a phase locked loop CMOS logic IC used in motor speed control, FSK modulation, tone decoding, voltage-to-frequency conversion, data conditioning and synchronization, frequency discrimination, frequency multiplication and synthesis, and FM modulator and demodulator, due to its high VCO linearity, low frequency drift, low dynamic power consumption, and wide supply voltage range.

The circuit consists of oscillators IC1a and IC1b which are made up of two NAND gates. These are logic gates which produce HIGH output in the event of one or both inputs being LOW. They are responsible for low frequency oscillation which drives the analog electronic switch. The switch operates by opening and closing with the sequence and pattern of oscillation. The supply of the voltage will charge the capacitor C3 via the resistor R2 when the switch is closed while C3 discharges through the resistor R3 when the switch is open.

Electronically Designed Siren Circuit Diagram



The voltage used by capacitor C3 is used to regulate the VCO of IC3 which is a phase-locked loop logic IC. This enables one output to be a modified audio. The sound of the siren can be altered by changing the values of the resistors and capacitors that will include some experimentation to adjust the sound. The duration and time of operation of operation is determined by the combination of R1 and C1 while the frequency of the produced sound is handled by the combination of R4 and C2. Lastly, the changing of sound is controlled the R3 and C3 combination.

The electronic siren system is ideally used in warning equipments in the field of police vehicles such as cars and motorcycles, ambulances, fire trucks or engines, and other types of emergency vehicles. When used on stationary places, there are more effective in security & protection, home alarm, water alarm, and public alert systems which provide alarming sound to municipalities and cities, in establishments like plants, factories and locations with potentially dangerous materials. They are also utilized in open spaces, halls and arenas. The most important feature that they provide is in cases of emergency situations in which they are being used for large warning systems. In choosing an electronic siren, the features such as light weight, high intensity shell, high reliability, and good quality with excellent workmanship, should be considered.