# 20 LED Rear Bike Light Flasher circuit using 555

This is 20 LED Rear Bike Light Flasher circuit using 555. Currently, traffic is convenient. The road is in good condition. Causing the car to run at higher speeds.

Cycling is so more dangerous. Especially at night. Even if there is a reflector attached to the back of the bicycle. But may not be visible.

A good solution is to create a bicycle taillight or a bike tail LED light flasher. It is Bike Blinking Safety.

Cr: Photo from Cycle Torch

It is easy that buy it in amazon.com But who are us? Electronic inventor, Right? Take time to create it better. Learning is always worth.

Imagine we just learn the 555 timer. We want to use it and a lot of super bright LEDs.

Yes! We can. Look:

## Operation of the circuit

See int the circuit diagram.

Use NE555 is Oscillator to produce an output signal out of at pin 3.

Which output frequency determined by R1, R2, C1.

And the output is a square waveform.

When it is high voltage. It goes to pin B of Q2. And the Q2(NPN transistor) runs. Make LED1 to LED10 lights up.

However, if the output signal is “low”. And, the voltage is 0 volts.

No voltage to bias Q2. It does not work.

Recommended: How does NE555 timer circuit works

In contrast, the Q1(PNP transistor) will work. To drive LED11-LED20 are bright up.

Then, the high voltage comes again. Q2 and these LED1-LED10 run again too. Both sets of LED lights will blink alternately

We may use battery AAx4 (1.5V x 4 = 6 Volts). Makes can use a long time than 3 months. When using 3 hours every day. Or we can AC dynamo as a power supply source.

It is a good idea for saving money to buy the battery and reduce Chemical waste. But must have DC regulate as well.

#### Parts you will need

IC1: 555 timer
LED1-LED20: LED as you want
C1: 1uF 50V Electrolytic
C2: 0.1uF 50V Ceramic
Q1: 2N2905,IC=0.6A, VCE=40V PNP Transistor
Q2: 2N3053,IC=0.6A, VCE=40V NPN Transistor

0.5W Resistors, 5% Tolerance
R1: 4.7K
R2: 100K
R3: 150 ohms
R4: 220 ohms
R5-R14: 100 ohms

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