Fog horn circuit

Fog horn electronic circuit project

A very simple fog horn electronic circuit project can be designed using three transistors and some other common electronic parts . This fog horn electronic circuit project is activated when the push button is pressed .

When the push button is pressed the 100uF capacitor will take time to charge and this will provide the rising pitch and this will provide the rising pitch and volume . When the push-button is released, the level and pitch will die away. This electronic project circuit must be powered from a 9 volt dc power supply ( it can be powered from a 9 volt battery) .

I don't know if it's realistic, but it's worth a shot.
Last edited:
Hi Justin,

I did find this one and gave it a try... However I was not able to get it to work... Not sure what I am doing wrong on it... I'd also like to find one that would work off a 555 timer...
Hmm, idk. I'll post other circuits I found, but they aren't fog horn circuits.
Electronic horn circuit for motorcycle and electric cars
Speaker motorcycles or electric cars are generally the use of electromagnetic vibration, and its interior has a set of coils. Power resulting from the magnetic field, the pull of the diaphragm sound, it has the advantage of simple structure. But the work current, generally up to minimum operating current of 1.5A, while the additional high-mounted bass cochlear ear speaker, working current up to 3A, use of loudspeaker damage to switches and lines easily, here are a low-power Electronic horn high loudness.

Circuit as shown. NE555 constitute audio oscillator circuit, the audio signal through its output pin 3 directly coupled to the transistor VT1, VT2, VT3 a composite tube amplifier circuit amplifies the Y and then promote the speakers sound, due to power amplifier using three composite amplification, so The large magnification, so the circuit power consumption, high impact, to 122dB, was determined that the operating current is less than 0.5A. Production, the speaker Y with 4O, 5W or more small diameter moving coil electric horn tweeter, such as the number can be found moving coil speaker is cylindrical siren would be more effective; adjust the pronunciation of R can change the Y effect. Can also be changed to realize the value of C1. Note Y to install the flaps.
555 Loud Horn
Here is a good quality and low cost project of a very loud 555 horn circuit. The circuit can be used as horn for bikes and other vehicles. It can also be used for many other purposes like as a siren circuit, buzzer circuit etc. The circuit is using only few components due to which you can easily fit
it in a small box with speaker.
The heart of the circuit is a 555 timer IC that is wired as an astable multivibrator here. By adjusting the 100K variable resistor you can select the desired tone of the horn. A TIP125 darlington transistor is used to amplify the output of the 555 IC. The operating voltage of the circuit is 9 to 12V DC. For speaker use an 8 Ohms 1 to 5 watt loud speaker. Loud sound will be received on 12V DC.

Train Horn
Last edited: