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Bicycle turn indicator lights circuit diagram

Bicycle turn indicator lights circuit diagram

Bicycle turn indicator lights are something that helps us to have a safe ride. But not every bicycles are equipped with these lights. In that case its our responsibility to make one to ensure safety. So here is how you can make your own bicycle turn indicator lights to enjoy a sweet and safety ride with your bike.



The circuit is very easy to understand and very few components are required to build this bicycle turn indicator lights circuit. The circuit is powered by a simple portable 9V alkaline battery which suit very much for this application. 9 LED’s are chosen for making a indicator for each side (Left and right) that makes a total of about 18 LED’s in this circuit. I have marked the separate LED sets in the diagram as “Left indicator” and “Right indicator”.

I have chosen orange LED’s rated 2.4V and 20ma for the indication lights. 9 LED’s are connected as 3 LED’s a set in serial and then connecting these sets parallel together. This option allows us to add more LED’s using the voltage provided by the battery. You need to add a current limiting resistor to control the current flow through LED and prevent it from damaging it. This is given by the formula 

R = Vcc – VLED / ILED

So using this formula in our circuit for each indicator, we get

R = 9 – 3 * 2.4 / 20ma 

   = 90 ohms ( 100 ohms is the nearest value for resistor)

The similar resistor value goes for all the resistors R2….R6 .


SW1 is a toggle or SPDT switch that allows only one indicator to light up at a time. Lighting of indicator toggles for change in position of this switch. Whereas Switch SW2 is a simple push button that provides the connectivity to the circuit from the battery. So this switch controls the power to the indicator lights. The maximum capacity of the battery is 550mAh. And the total current consumption of the circuit will be 60mA since only one indicator lights up at any instant.

Usage of indicator for 1 hour will be = 60ma * 1 hour

                                                    = 60mAh.

So the total duration the indicator can run using the battery is  = 550mAh / 60mAh = 9 hours (approx)


The positioning of these indicators are very important in your bicycle. Position each indicator (9 LED’s) to your Left and Right of the bicycle. Wire the indicator to the handle of your bike. Place the switch SW2 to the right of your handle. The switch SW1 goes to your left of the handle. You can switch the positions as you wish. So to activate the indicator make a gentle press in the switch SW2 and toggle the switch SW2 to change the indicator which you want to light up. Pressing the SW2 again will turn off the indicator.

Place the switch SW1 in such a way that toggling it right will turn up the right indicator and toggling left lights up the left indicator. I hope everyone likes this simple weekend project, do try it out.


  • You can also add an indicator to the front of your bike by adding up another two set of indicators but make sure you use a battery with sufficient current rating.
  • You can replace the 9v/550mah battery with any battery of yours but make sure you replace the Current limiting resistors.

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