Flashing LED with a transistor Simple and Inexpensive

Often we need to put in a circuit a small flasher, for any warning or even a simulator alarm or security camera on. But making a common circuit flashes with two transistors or using the LM555, besides being expensive, more expensive project and increases its physical size. Here in this article we will see a LED flasher that uses only one transistor and three passive components. But first let's see the common flasher.

How to Make an LED flasher

Make a flashing LED is easy, depending on your needs, you can use a 555 timer integrated into the LED flasher circuit. You can also use a common circuit with two transistors in the circuit as we see below. This circuit is called the astable multivibrator is a circuit that has no stable state.

List of material

Q1 and Q2 - BC548 transistors or any general purpose NPN transistor

LED1 and LED2 - Common LEDs - any color

R1 and R4Resistor 470 ohm 1/8 ​​Watt

R2 and R3Resistores 22 kohms 1/8 Watt C1 and C2

Electrolytic Capacitors 10 to 100 pF per 16 Volts or more.

Flashing LED with Transistor

First things first, our flasher LED with a transistor that is simple to build and very cheap. Although it appears something supernatural, the operation is simple. A resistor 1k ohm loads slowly electrolytic capacitor 220 uF 25 Volts X until the voltage becomes high enough to release the emitter-base junction of the transistor 2N2222.

At this point the transistor drive quickly, and partially download the 470uf capacitor for LED, which lights quickly. The 100 Ohm resistor works just as current limiter LED. Esse simple and functional flasher LED is WELL INTERESTING, this Configuration schema ele down trabalhou com uma tensão from 10 Volts to 13 Volts, and as the tensão subia the range of flashes decreased.

The transistor used was a 2N2222 is an NPN, he had a very stable behavior, seems to work reliably in this circuit, but other transistors can be tested is clear that few will work. Unlike the version with two transistors that can use any NPN type transistors, since this version presented here transistor requires some special qualities that we will see below.

  Tunnel effect

We called tunnel effect, in this case the tunnel effect "in quantum mechanics is the event of a particle through a region where the potential energy is larger than its total energy - this is insurmountable barrier in classical mechanics, since the kinetic energy of the particle would be negative in the region "[Wiki]

So it is with a tunnel diode which is a semiconductor type which is able to operate very quickly in the microwave frequency made ​​possible by using so-called quantum mechanical tunnel effect. This means that there are few transistors that have this characteristic tunnel diode, the most common and easiest to find is actually the 2N2222.

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