Various sound generating project is posted in Alarm and Sound Generation Section. Now here is very simple an easy to construct electronic project called Toy Siren using CD7400 (IC1).
Circuit Description of Toy Siren Circuit Using CD7400
The heart of the project toy siren circuit is quad-2-input NAND gate IC CD7400 (IC1). IC1 (CD7400) is a cheap easily available IC and it consist four NAND gate. Two NAND gate out of four is configured as low frequency oscillator and another two NAND gate as high frequency oscillator.
When output of low frequency oscillator become low, then diodeD1 goes in saturation state and as a reset resistor R3 and R4 become short. When output of low frequency oscillator become high then diode D1 does not goes in saturation state and as a result resistance R3 and R4 joined to the circuit of high frequency oscillator. The effect of these resistors is shown in output of high frequency oscillator.
The output of IC1 is given to base of PNP transistor which is here worked as an amplifier and is given to loudspeaker LS1.
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PARTS LIST OF TOY SIREN CIRCUIT USING CD7400.
| Resistor (all ¼-watt, ± 5% Carbon) |
| R1, R2, R6 = 2.2 KΩR3 = 10 KΩ
R4 = 1.2 KΩ R5 = 2.7 KΩ |
| Capacitors |
| C1, C2 = 25 µF, 25V (Electrolytic Capacitor)
C3 = 0.5 µF (Ceramic Disc) C4 = 0.05 µF (Ceramic Disc) |
| Semiconductors |
| IC1 = CD7400 (CMOS Quad two input NAND Gate IC)
T1 = SK100B (Medium Power silicon PNP Transistor) D1 = 1N4148 ( Small Signal Diode) |
| Miscellaneous |
| LS1 = 8Ω Loudspeaker |