Many electronics circuits and projects for learning in simple ways.

Blinking 2 LED circuit using NPN transistors

I like Blinking 2 LED circuit using NPN transistors. There are many circuits here is one of blinking circuit. We call it Astable Multivibrator. Often we know it 2 LED Flasher circuit, in this we use PNP transistor.

But now we use 2 NPN transistor. We normally see it in a lot of circuit as oscillators. Both transistor work alternately like the automatic switches that are alternate working. The collector of Q1 or Q2 makes the frequency signal.

Blinking 2 LED circuit using NPN transistors

Operation of the circuit
To begin with, suppose that the Q1 run first. Then LED1 should grow more brightly.
It makes the current to flow through LED1, R1, and the collector-emitter of Q1. At the same time, some current will flow through LED2, R4, and to charge into C2 until full. The voltage BE is lower than 0.7V. So Q1 turns off, LED1 goes out.

Next Q2 start working, LED2 also grows more brightly. The C1 begins to charge until full, VBE of Q2 is lower than 0.7V. It turns off, LED2 goes out.

After that Q1 will turn on and LED1 to grow up again. the circuit working will repeat loop in like this.

The bicycle tail light for my son.
The principle of this circuit, I built the bicycle tail light flashing for my son.At first he was very appreciate. But he embarrassed every time, friends to tease. Because it’s funny. I used a hot food box, because prevent water heat resistant and very economical. And more importantly, it increases the safety of the children. When riding a bicycle in the evening.


3V Blinking 2 LED circuit using transistor

My son want to builds simple LED flasher. I choose this circuit because easy we assemble all parts on the bread board and use 3V AA battery, use BC549 and not need Resistor limit current to LEDs as Figure below.


3V Dual LED flasher circuit diagram.

and He tests it as the video below.

Keep reading: ‘Fast blinking LED bike light circuit’ »

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