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 each LED use voltage about 3 – 4.5V
We want this circuit for long time using so use the LED voltage is 3V only. And makes them to blinking as the LED flasher.
How this circuit works
This is simple transistor oscillator circuit as 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 turn off itself, so the cycle repeats again.
How to builds
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.