Steam Whistle Circuit using 741 IC

The project “Steam Whistle Circuit using 741 IC” produces a sound similar to that of a steam locomotive whistle. Here, in the circuit Transistor T1 and T2 from a multivibrator, the frequency of which is set by preset VR3. This is the ‘toot’ part of the whistle. Transistor T4 amplifies white noise generated across the reverse-biased transistor T3. White noise and toot mixed by IC1.

The ratio of these is set by preset VR2. IC1 is the most popular and low-cost IC 741 and is used as a low-frequency multivibrator, the output from IC1 is fed to a simple amplifier based around TBA810 IC, IC2.

The positive 12V could be fed to the circuit by a push switch near the controller or by the model train itself using a reed micro switch.

circuit diagram of steam whistle

PARTS LIST OF STEAM WHISTLE CIRCUIT USING 741 IC

Resistors (all ¼-watt, ± 5% Carbon)

R1 = 47 KΩ, 0.5W

R2, R5 = 20 KΩ

R3, R4 = 15 KΩ

R6 = 4.7 KΩ

R7, R9, R10 = 10 KΩ

R8 = 150 KΩ

R11 = 1 KΩ

R12, R13 = 100 KΩ

R14  = 220 KΩ

R15, R16 = 100 Ω

R17 = 1 Ω

VR1 = 500 KΩ

VR2 = 10 KΩ

VR3 = 47 KΩ

Capacitors

C1, C2, C7 = 0.02 µF (Ceramic Disc)

C3, C6, C14 = 0.1 µF (Ceramic Disc)

C4 = 0.04 µF (Ceramic Disc)

C5 = 10 µF, 16V (Electrolytic Capacitor)

C8, C9, C10 = 100 µF, 16V (Electrolytic Capacitor)

C11 = 470 µF, 16V (Electrolytic Capacitor)

C12 = 0.0047 µF (Ceramic Disc)

C13 = 0.0015 µF (Ceramic Disc)

Semiconductors

IC1 = 741 (General purpose Op-amplifier)

IC2 = TBA810 (Audio Amplifier IC)

T1 – T4 = BC108 (Silicon NPN Transistor)

Miscellaneous

SW1 = On/Off switch

LS1 = 8Ω/4Ω speaker

Check out other interesting alarm circuits posted on bestengineeringprojects.com

  1. Electronic Siren Circuit
  2. 12 Tones Door Bell
  3. Rain Sound Generator Circuit
  4. Simple Warning Alarm Circuit 
  5. Beeper Circuit | 555 Timer Project

Leave a Comment