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Last Updated: September 23, 2013

Horn Interrupter (flasher)

Motorcycle horn is basically the least seen to be modified with regards to the sound, one momentarily press of the horn switch, one sound, while as long press emits a continuous annoying sound. Why not make it lively  by just putting an interrupter (Flasher) to alternately on/off the horn to produce a machine gun like sound when the switch is press. Using a 555 timer ic that will be configured as an astable multivibrator, and a relay that can handle 10-15 amps, will do this trick. Moreover you do not even have to cut any existing wire for this to work and can revert the HORN system back to normal, in case it is not allowed in your area by the traffic law enforcers.


Horn works very simple, the negative supply is the path that is being used on the HORN switch rather than the positive line. Why? perhaps to lessen and avoid voltage spike that may affect the ignition when the horn is activated drawing large current just to move its diaphragm to create the sound, such as the CDI and ECU of fuel injected machines, i may be wrong here,still that was my findings about the horn wiring on a motorcycle.

Photo shown is the basic motorcycle horn wiring without automotive relay. Basically an additional relay is fitted by others just to preserve the switch contact from wear since the configuration shown, the switch will always spark corroding its contact.

In this kind of setup, one momentary press of the horn switch, one sound emitted by the horns, one long press, one long annoying sound.

Here is a hint, instead of one press one sound, why not try the one press two successive sound, and one long press, will produce, a flashing or strobing sound. Any IDEA? we'll i have and you came to the right place, and the set-up will be very simple. no need to rewire, and no means of cutting your existing wire, so that in this kind of setup, once you did not appreciate the sound then unplugged the module and plug the horn, you'll basically be back to the original set-up.


Again the circuit is very simple and no need for PCB fabrication. Copper board with pre drilled holes will do just fine for this setup or, u can go parts to pin soldering technique, components are soldered pin to pin.

Shown is a led flasher, This will be the base circuit of this horn interrupter by just putting a few other components like a mechanical relay, resistor, and or a driving transistor, plus terminals and connector, VOILA!!! a simple horn effect in as single push of a button.


Combining the two will be your complete horn flash system.


A completed PCB of the horn interrupter.

PCB design by DIPTRACE

For the Audio file of the said interupter, note: the horn used was one part of the bosch snail horn LOW frequency and the other is the stock OEM motorcycle horn that was connected in parallel, the sequence of the sound corresponds to the press of the horn from 2 second push, 1 second, and a long press of the horn switch.