This is a fast blinking LED bike light circuit For safety when the bike at night. We use two-NPN-PNP transistor oscillator circuit and RC circuit only show on 4 LEDs use low current.
We take the four LEDs to parallel. Because of each LED use voltage about 3 – 4.5V
We want this circuit for a long time using so use the LED voltage is 3V only. And makes them blinking as the LED flasher.
Figure 1 Testing the LEDs in parallel. They use current about 0.077A.
But we use them in switching so low
How this circuit works
This is a simple transistor oscillator circuit as a flip-flop. We use a simple RC. Here is the schematic of my two-transistor LED flasher: The RC circuit is connected to the base of the NPN transistor (2N3904) and it gives the signal to the PNP transistor (2N3906) to turn on the LED. When the PNP transistor is ON, it discharges the capacitor and it turns off itself, so the cycle repeats again.
Parts will you needs
Q1: 2N3904, Transistor General Purpose BJT NPN 40V 0.2A
Q2: 2N3906, Transistor General Purpose BJT PNP 40V 0.2A
C1: 22µF 25V, Electrolytic Capacitors
C2: 100µF 25V, Electrolytic Capacitors
R1: 330K, 1/4W Resistors tolerance: 5%
R2: 15 ohms, 1/4W Resistors tolerance: 5%
LED1-LED4, Color as you like
Battery, Switch, and more
How to build
Today I want tech my son assemble circuit on cardboard because he did not want to use PCB. We use the cardboard from old Desktop calendar that unused. We design the components layout on a paper. Then stick it on the cardboard with glue. As Figure 3
Figure 3 the layout on cardboard
Next step, to use iron spikes holes to insert pins as Figure 4
And Then, put the components on layout as Figure 5
After that, to use pin devices Or copper wire connected as Figure 6
Next, Solder pins and copper wires to complete. as Figure 7
Then, Test to use it as video below
And then,Apply glue pin devices, the access point and devices. In order to prevent vibration. As Figure 8
Last, To bring the circuit trial, mounted on a bicycle as Figure 9
and test it at night as video LED flasher good look and low current use.
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13 thoughts on “How to make fast blinking lights for bike”
Hi Salim Khan,
Thanks for your feedback.
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Great circuit in which I am planning on making, but before I do, I was wondering what is the wattage of the 15 ohm resistor in the circuit?
It looks like a 1/2 watt resistor, am I right?
Thanks for the help and your contributions to those in the community that share the same interest in electronics.
What represent R1 330K?
You can use 100K to 390K resistor.
Thank you so much.
Yes, you can use 1/2W resistor.
Same components can for 12 v supply and 12 v beeper
R1 Is A Feedback Resistor For The Osccillator Circuit
OOPs!!!!! Oscillator Circuit
What is the Ohm of R1 in the Fast Blinking LED Bike Lighting Circuit? Can’t see it in the text
Thanks you like this circuit.
We feel sorry, forget to put parts list.