2-Pin Motorcycle Turn Signal Indicator Beeper Circuit

A simple construction procedure of a motorcycle electronic turn signal with beeper circuit has been thoroughly explained in this article.
Normally, the electro-mechanical types of turn signal indicators are not reliable due to low consistency and vulnerability to changing weather conditions. The present design easily withstands the above parameters and more importantly consists of an attached buzzer indication facility. The inclusion of an audible signal makes it sure that once the required deviating turn is completed by the vehicle; the driver remembers to switch off the unit and save precious battery power

Conventionally a turn signal indicator will require three output terminals for its correct operation. Uniquely the proposed circuit works with just a couple of terminals, and moreover incorporates a built-in buzzer. Here we explain a simple motorcycle electronic turn signal with beeper circuit.


Also popularly known as “flasher with buzzer,” turn signal actuators are indispensable piece of devices for every vehicle. The device is particularly used for switching or flashing the side indicator lights (left or right) of a vehicle while making a turn or a deviation from its normal path. Basically the flashing of the lamps acts like a warning signal and makes it easier for the other vehicles to identify the track of the indicating vehicle. This averts a possible collision and misunderstanding between vehicles. The device thus specifically helps in avoiding accidents and mishaps.

Nowadays many folks prefer the above devices accompanied with an audio indication like a buzzer or a beeper which may produce a rhythmic note with the light switching. This facility proves to be useful in two ways, first: it assures the driver regarding the perfect working of the entire system and second: when the necessary deviating move or a turn is completed, the audio note keeps reminding the driver that the unit is still ON and needs to be switched off, thus saving precious battery power and false indications.

The present circuit of a motorcycle electronic turn signal beeper has been specifically designed by me and tested thoroughly, in fact I have already sold more than 90,000 pieces of them in the market and the demand keeps growing. The circuit described here is very unique because of the following reasons:

· Its 2-pin design makes it compatible with almost all 2 wheeler wiring system.

· Since it is electronic and solid-state becomes very long lasting and weather proof.

· A built-in high quality piezo buzzer makes it a better choice with the folks.
Parts List

R1, R2, R3 = 10K,

R4 = 33K,

T1 = D1351,

T2 = BC547,

T3 = BC557,

C1, C2 = 33uF/25V

D1 = 1n4007,

COIL = Buzzer coil

Circuit Description

Let’s try to understand its functioning with the following points:

From the circuit shown alongside we see that the whole circuit is built around just three inexpensive active components T1/T2 and T3.

A few other passive components in the form of resistors and capacitors are used to initiate the flashing action and sustain it as long as power remains switched ON to the circuit.

When power is first switched ON, capacitor C1 slowly charges via R1.

The moment it reaches its full charge, T3 is able to conduct and provides some sort of an initial biasing voltage to T1/T2.

T1/T2 partially conduct and in the process turns ON T3 much harder through R2, because now T3 receives full biasing through R2, T1 and the lamps switch ON.

The lamp now receives full power through T1/T2 and ignites.
But around this time C1 almost instantly discharges through R1, T1/T2 and the lamps, blocking the emitter of T3. T3 immediately stops conducting, so does T1/T2 and the lamp shuts-off influencing a fresh cycle to begin. The lamps thus start flashing.

D1 and C2 are placed to filter out any AC component or spike that may be present in the auto electrical while it’s in motion.

The circuit of this motorcycle electronic turn signal beeper also incorporates a small yet powerful buzzer circuit connected in parallel to the supply line.

During the flashing process, at the instants when the lamp is turned ON the buzzer stops sounding and vice versa. This happens because the lamps suck out almost all the power from the circuit and the buzzer is not able to receive the required voltage and is able to beep only when the lamp shuts off in between.

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  1. Hi Swagatam

    Nice circuit but parts values are missing?



  2. Sorry about that Sam,
    I'll do it right now...
    Thanks for pointing out the mistake...:-)

  3. Thanks. Looks complete and great.

    I have couple of D313 transistors which may be used instead of D1351. What do you think? Moreover you have a couple of circuits for LED lights, will the above circuit work for LEDs too or just bulbs.

    Regards and thanks


  4. Thank you Sam!
    Yes D313 is an equivalent of D1351 so you can use it, however put a small piece of heatsink over it to avoid overheating of the device if you are using the circuit as a bike flasher.
    No, LED will not work with this circuit, this circuit will support only incandescent type of lamps.


  5. Can a n channel MOSFET like the IRFZ44N be used in place of the D1351.

    1. Hi Paval,

      I don't think this circuit will work with a mosfet, however you can give it a try and report back here, so that others can also learn about it....

  6. where should i connect the switches for left and right turn?

    1. The switch is present in the vehicle, an auto electrician will know how to wire them up.

  7. G'Day Swagatam, great site! can you please explain what T3 is doing in this circuit? does it initially conduct upon c1 building charge then turn on t2 and t1
    You mention in the explanation of the circuit that after c1 charges t2 is turned on - is that by t3 being turned on?
    Thanks for a great site

    1. I have corrected the above explanation, please refer to it,

      Thanks for indicating the issue.

  8. how to make it glow alternatively also is it possible to adjust the speed..please do a circuit such that it will blink fast 2 or 3 times and after 5 sec again blinks like that :)

  9. I want to replace my stock flasher with a one which can flash LED Bulbs. Do you have a circuit that can do it or can this circuit be used with some modifications. I need a load independent circuit so the led wattage can vary.

    1. the above circuit is load dependent, you can try the first circuit from the following article:

      replace the LED/1k with a relay coil, then you can use the relay contacts for flashing the LEDs in series with the supply voltage.

      use a diode in parallel with the relay coil

  10. Hi, are the resistors are half watt or quarter watts


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