There is a strong need to make the LED blink to enhance attracting a person’s attention to the signal. But to make a complex circuit there is simply no time and space to place radio elements. I'll show you a circuit consisting of just three that will make the LED blink.

The circuit works well on 12 volts, which should be of interest to motorists. If we take the full range of the supply voltage, then it lies in the range of 9-20 volts. So this device can find a lot of applications.

This is a truly super simple circuit to make an LED blink. Of course, the circuit contains a large electrolytic capacitor, which can steal a lot of space, but this problem can be simply solved by using a modern element base, such as an SMD capacitor.

Note that the base of the transistor is hanging in the air. This is not a bug, but a design of the circuit. The base is not used, since the operation uses the reverse conductivity of the transistor.

Such a flasher can be assembled by hanging installation in about fifteen minutes. Put on the heat shrink tube and blow it with a hot air gun. And now you have a generator for blinking LEDs. The blinking frequency can be changed by increasing or decreasing the capacitance of the capacitor. The circuit does not need to be configured and works immediately if the circuit elements are in working order.
The flasher is very economical to operate, reliable and unpretentious.

Diagram for connecting a flashing LED to a 220V network, used to scare away thieves from the front door of a house or apartment. The flashing LED is installed on the front door and flashes very brightly and noticeably at night. The question is, why this “illumination”, and what is the point of it?

I answer, a bad person is coming to rob the apartment, and there the LED is blinking... blinking suspiciously... Suddenly the security forces will arrive, or worse, the police. And he changes his mind about going into the apartment. Of course, a flashing LED will not scare off an experienced and very technically advanced thief.

But if all your valuables are a TV, a refrigerator and grandfather’s boots, such a professional will not bother you - most likely you will be a mentally limited gopot who knows about alarms only from films. For such a “contingent”, a flashing LED is the protection they need (they will also change the area, and they will think that the LED captured their faces).

In general, you need to purchase a flashing LED, such as the L-56BID, and install it on or above the door. The only issue is with the connection. If you have an extra phone charger or another power supply - a plug, you can simply connect the LED to it through a current-limiting resistor.

Schematic diagram

If the only place of possible power supply is the electrical network, then you can connect the flashing LED according to the very well-proven circuit shown in the figure. Excess voltage drops across resistors R1-R3. There are three resistors of 75 kOhm, and not one of 220 kOhm, because it is advisable to make the line longer to ensure that breakdown is avoided.

Diode VD1 serves as a rectifier. Capacitor C1 is storage. Now the most interesting thing is that the circuit contains a zener diode VD1. In principle, if the HL1 LED were not blinking, there would be no need for this zener diode, as well as for resistor R4.

But NI is a flashing LED. Therefore, at those moments in time when it goes out, its resistance increases greatly and, accordingly, the voltage dropping across it also increases. If there is no zener diode VD1, the forward voltage on the NI at the moment of its extinguishing will reach 300V and maybe even more. Which will lead to its failure.

There is also a stabi-litron here, which will limit the voltage on the LED at those moments when it is turned off.

Rice. 1. Schematic diagram of the power supply for a flashing LED.

The stabilization voltage of the zener diode does not necessarily have to be 12V. The zener diode can be of any voltage that the LED can normally withstand in the off state. But not lower than its direct voltage in the burning state. That is, somewhere from 3V to 30V.

Almost any zener diode for any voltage within these limits. Accordingly, capacitor C1 must be at a voltage not lower than the voltage of the zener diode.

Resistor R4 is needed in order to limit the discharge current of the capacitor through the LED at the moment of its ignition. In principle, you can do without it, but there is a high probability that the LED will not last long.

So R4 is here just in case. R4 is especially relevant when using a zener diode for voltage at the upper limit (up to 30V). Because the higher this voltage, the greater the current surge will be at the moment the LED lights up.

Details and setup

Instead of L-56BID, you can use any flashing LED. If the brightness of the glow is not enough, you need to reduce the total resistance R1-R3, but it is desirable that these resistors be the same.

This section contains circuits of light pulse generators or, more simply, flashing lights. They can be installed on children's toys, used in attractions, or placed in a visible place in the car to simulate the action of a security device.

thyristor flasher circuits

Relatively simple “flashing lights” are obtained by using SCRs. True, the peculiarity of the operation of most thyristors is that they open when a certain voltage (current) is applied to the control electrode, and to close them it is necessary to reduce the anode current to a value below the holding current.

By the way: what is a thyristor And how to check it you can read

If the thyristor is powered from an alternating or pulsating voltage source, it will automatically close when the current passes through zero. When powered from a constant voltage source, the thyristor will not simply close; special technical solutions will have to be used.

The diagram of one of the variants of a “flashing light” using thyristors is shown in Fig. 1. The device contains a short pulse generator based on a unijunction transistor VT1 and two stages using thyristors. An incandescent lamp EL1 is connected to the anode circuit of one of the thyristors (VS2).

This is how the device works. At the initial moment after power is applied, both SCRs are closed and the lamp does not light. The generator produces short powerful pulses at intervals determined by the parameters of the R1C1 chain. The very first pulse will arrive at the control electrodes of the thyristors, and they will open. The lamp will light up.

Due to the current flowing through the lamp, the SCR VS2 will remain open, but VS1 will close, since its anode current, determined by resistor R2, is too small. Capacitor C2 will begin to charge through this resistor and will be charged by the time the second pulse of the generator appears. This pulse will lead to the opening of the thyristor VS1, and the left terminal of the capacitor C2 according to the circuit will be briefly connected to the cathode of the thyristor VS2. But even such a connection is enough for the thyristor to close and the lamp to go out.

Thus, both thyristors will be closed, capacitor C2 will be discharged. The next pulse of the generator will lead to the opening of the thyristors, and the described process will be repeated. The lamp flashes at a frequency half that of the generator.

For the elements indicated in the diagram, you can use an incandescent lamp (or several lamps connected in series or parallel) with a current of up to 0.5 A. If you use all the capabilities of the indicated thyristors, it is permissible to use a lamp consuming a current of up to 5 A. In this case, for reliable closing SCR VS2, the capacitance of capacitor C2 must be increased to 330...470 μF. Accordingly, it will be necessary to increase the capacitance of capacitor C1 so that in the periods between generator pulses, capacitor C2 has time to charge. The VS2 thyristor should be placed on a small radiator.

The “flashing lights” parts are mounted on a printed circuit board (Fig. 2) made of one-sided foil-coated getinax or fiberglass. Oxide capacitor C2 - necessarily aluminum, series K50-6, K50-16, K50-35.

If the lamp current does not exceed 0.5 A, one of the SCRs can be replaced with a less powerful one, for example, KU101A (VS1 in Fig. 3). Since the voltages on the control electrodes of the thyristors at which they open are different, a tuning resistor R2 is introduced into the device, with the help of which the optimal mode of their operation is selected. In addition, the resistance of the resistor (R3) in the anode circuit of the thyristor VS1 is increased.

True, then the printed circuit board will change a little. It will look like this:

Setting up designs comes down to setting the required frequency of lamp “blinking” by selecting capacitor C1. If the incandescent lamp lights up but does not go out, it means that either the thyristor VS1 does not close (you should increase the resistance of the resistor R2 in the first “flasher” or R3 in the second), or the capacitor C2 does not have time to charge. Then it is advisable to reduce its capacity, and even better, the switching frequency. In the second “flasher” you need to set the trimmer resistor slider to a position in which both SCRs operate stably.

Additional useful materials:

Answer

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I bring to your attention a simple flashing light that even a beginner can assemble in 5 minutes.

The operating principle is as follows: due to the drop in voltage across the thyristor, the capacitor is charged through a powerful resistor R1. When the voltage on the capacitor reaches the threshold, which is set by variable resistor R2, the thyristor opens and the lamp lights up. Diode V2 is necessary to protect the capacitor from breakdown. Well, now about the details - the resistor R1 must be powerful - mine is 2W, but it still gets hot, so it’s better to take a 2.5W or even a wire PEV (they come in up to 10W). You need a high-voltage capacitor, my voltage on its plates is 50V, but it can be higher, so it’s better to take it with a reserve. The thyristor is selected depending on the load - I successfully used KU202N, but also suitable with the letters K, L and M and also KU201I. The diode is not necessarily D226B, I used D7E and KD202D - both withstood the current and did not get hot, I think that nothing will happen to the foreign 1N4001 and 1N4007 either. The variable resistor is selected based on the unlocking current of the thyristor - it is selected experimentally from 5K to 47K, any power.

This device can be loaded onto both a lamp and a Christmas tree garland. Or you can also complete one more arm with the opposite polarity and then the lights will blink in turn.