Vespa Scooter Turn Signal Help

Thread Starter


Joined May 14, 2006
I have an older Vespa scooter. The turn signal circuit is very primative. A thermal flasher controls a lead to the handle bar switch that selects the right or left turn signal. The turn signal "beeper" is a piezo buzzer on the "flashing line" to the handle bar. I recently purchased a product by a company called Kisan, that replaces the thermal flasher with a Pulse Width Modulator (PWM) unit that allows the turn signals to be used as running lights. I guess with a half duty cycle, the left and right turn signals both appear to be continuously lit at half brightness. When the turn signal is activated, the correct turn signal flashes at full brightness.

My problem is with the piezo buzzer in the circuit, it sounds continuoulsy since the turn signal circuit always has a voltage on it. I've unplugged it, but now I don't have a turn signal beeper.

Is there a circuit design that would ignore the half duty cycle of the running lights but pass the flashed full duty cycle of the turn signals to the beeper? In this way I could have the best of both worlds -- running lights and a turn signal beeper. Thanks for your help.



Joined Jan 10, 2006
Something simple like this should work.

Not knowing the Frequency or Duty cycles, you may have to experiment with values a little.
Start with say a 22K input resistor, 10 μ F capacitor to filter the PWM, and perhaps a 5K trimpot.
A BC547 or similar GP transistor should suffice as Piezo's draw only a small current.
Should all fit into a small space near the Buzzer. Adjust the trimpot so nothing is heard until you use the indicators.