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
Then, Test to use it as video below
and test it at night as video LED flasher good look and low current use.
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