There is a strong need to make the LED blink in order to increase the attraction of human attention to the signal. But to make a complex circuit there is simply no time and place to place radio elements. I'll show you a circuit with just three that will make the LED blink.

The circuit works well from 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 truly a super simple circuit to make an LED blink. Of course, there is a large electrolytic capacitor in the circuit, which can steal a lot of space, but this problem can be simply solved 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 circuit design. The base is not used, since the work uses the reverse conductivity of the transistor.

Such a flasher can be assembled by hanging installation in about fifteen minutes. Put on a heat shrink tube and blow it with a hot air gun. And now you have a blinking LED generator. 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 with serviceable elements of the circuit.
The flasher is very economical in operation, reliable and unpretentious.

This section contains circuits of light pulse generators, or, to put it simply, flashers. They can be installed on children's toys, used in attractions, placed in a conspicuous place in the car to simulate the action of a watchdog.

thyristor flasher circuits

Relatively simple "flashing lights" are obtained using trinistors. True, the peculiarity of the operation of most trinistors 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 trinistor 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 trinistor will not close just like that, you will have to use special technical solutions.

A diagram of one of the options for "flashing lights" on trinistors is shown in fig. 1. The device contains a generator of short pulses on a unijunction transistor VT1 and two cascades on trinistors. An incandescent lamp EL1 is included in the anode circuit of one of the trinistors (VS2).

The device works like this. At the initial moment after power is applied, both trinistors are closed and the lamp is off. The generator generates short powerful pulses with an interval determined by the parameters of the R1C1 chain. The first impulse will go to the control electrodes of the trinistors, and they will open. The lamp will light up.

Due to the current flowing through the lamp, the trinistor 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 by the time the second pulse of the generator appears, it will be charged. This pulse will lead to the opening of the trinistor VS1, and the left output of the capacitor C2 according to the circuit will be briefly connected to the cathode of the trinistor VS2. But even such a connection is enough for the trinistor to close and the lamp to go out.

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

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

Details of the flasher are mounted on a printed circuit board (Fig. 2) from 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 trinistors can be replaced with a less powerful one, for example, KU101A (in Fig. 3 VS1). Since the voltages on the control electrodes of the trinistors, 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, increase the resistance of the resistor (R3) in the anode circuit of the trinistor VS1.

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

The adjustment of structures is reduced to setting the required frequency of "flashing" of the lamp by selecting capacitor C1. If the incandescent lamp lights up but does not go out, then either the trinistor 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 desirable to reduce its capacity, and even better - the switching frequency. In the second flasher, you need to set the trimmer resistor engine to a position in which both trinistors work steadily.

Additional useful materials:

Any novice radio amateur has a desire to quickly assemble something electronic and it is desirable that it work immediately and without time-consuming setup. Yes, and this is understandable, since even a small success at the beginning of the path gives a lot of strength.

As already mentioned, the first step is better to assemble the power supply. Well, if it is already in the workshop, then you can assemble a flasher on LEDs. So, it's time to "smoke" with a soldering iron.

Here is a schematic diagram of one of the simplest flashers. The basic basis of this circuit is a symmetrical multivibrator. The flasher is assembled from affordable and inexpensive parts, many of which can be found in old radio equipment and reused. The parameters of the radio components will be discussed a little later, but for now let's figure out how the circuit works.

The essence of the circuit is that the transistors VT1 and VT2 open in turn. In the open state, the E-K junction of transistors passes current. Since LEDs are included in the collector circuits of transistors, they glow when current passes through them.

The switching frequency of transistors, and therefore LEDs, can be roughly calculated using the formula for calculating the frequency of a symmetrical multivibrator.

As you can see from the formula, the main elements with which you can change the switching frequency of the LEDs is the resistor R2 (its value is R3), as well as the electrolytic capacitor C1 (its capacity is C2). To calculate the switching frequency, you need to substitute the resistance value R2 in kiloohms (kΩ) and the capacitance value of the capacitor C1 in microfarads (μF) into the formula. We get the frequency f in hertz (Hz or in a foreign manner - Hz).

It is desirable not only to repeat this scheme, but also to “play around” with it. You can, for example, increase the capacitance of capacitors C1, C2. In this case, the switching frequency of the LEDs will decrease. They will switch more slowly. You can also reduce the capacitance of the capacitors. In this case, the LEDs will switch more often.

With C1 = C2 = 47 uF (47 μF) and R2 = R3 = 27 kΩ (kΩ), the frequency will be about 0.5 Hz (Hz). Thus, the LEDs will switch 1 time in 2 seconds. By reducing the capacitance C1, C2 to 10 microfarads, you can achieve faster switching - about 2.5 times per second. And if you install capacitors C1 and C2 with a capacity of 1 microfarad, then the LEDs will switch at a frequency of about 26 Hz, which will be almost imperceptible to the eye - both LEDs will simply glow.

And if you take and put electrolytic capacitors C1, C2 of different capacities, then the multivibrator will turn from symmetrical to asymmetric. In this case, one of the LEDs will shine longer, and the other shorter.

More smoothly, the blinking frequency of the LEDs can also be changed using an additional variable resistor PR1, which can be included in the circuit like this.

Then the switching frequency of the LEDs can be smoothly changed by turning the knob of the variable resistor. A variable resistor can be taken with a resistance of 10 - 47 kOhm, and resistors R2, R3 can be installed with a resistance of 1 kOhm. Leave the ratings of the remaining parts the same (see table below).

This is what a blinker looks like with a smooth adjustment of the frequency of flashes of LEDs on a breadboard.

Initially, it is better to assemble the flasher circuit on a solderless breadboard and customize the circuit as you wish. A solderless breadboard is generally very convenient for all sorts of experiments with electronics.

Now let's talk about the details that will be required to assemble an LED flasher, the diagram of which is shown in the first figure. The list of elements used in the scheme is given in the table.

Name	Designation	Denomination/Parameters	Item brand or type
transistors	VT1, VT2		KT315 with any letter index
Electrolytic Capacitors	C1, C2	10 ... 100 microfarads (operating voltage from 6.3 volts and above)	K50-35 or imported analogues
Resistors	R1, R4	300 ohm (0.125 W)	MLT, MON and similar imported
	R2, R3	22...27 kOhm (0.125 W)
LEDs	HL1, HL2	indicator or bright at 3 volts

It is worth noting that the KT315 transistors have a complementary "twin" - the KT361 transistor. Their bodies are very similar and it is easy to confuse them. It would not be very scary, but these transistors have a different structure: KT315 - n-p-n, and KT361 - p-n-p. That is why they are called complementary. If instead of the KT315 transistor, KT361 is installed in the circuit, then it will not work.

How to determine who is who? (who is who?).

The photo shows the transistor KT361 (left) and KT315 (right). Only the letter index is usually indicated on the transistor case. Therefore, it is almost impossible to distinguish KT315 from KT361 in appearance. To reliably make sure that it is KT315, and not KT361, that is in front of you, it will be most reliable to check the transistor with a multimeter.

The pinout of the KT315 transistor is shown in the figure in the table.

Before soldering other radio components into the circuit, they should also be checked. Especially checks require old electrolytic capacitors. They have one problem - the loss of capacity. Therefore, it will not be superfluous to check the capacitors.

By the way, with the help of a flasher, you can indirectly evaluate the capacitance of capacitors. If the electrolyte is “dry” and has lost part of the capacity, then the multivibrator will operate in an asymmetric mode - this will immediately become noticeable purely visually. This means that one of the capacitors C1 or C2 has less capacitance ("dry") than the other.

To power the circuit, you will need a power supply with an output voltage of 4.5 - 5 volts. You can also power the flasher with 3 AA or AAA batteries (1.5 V * 3 = 4.5 V). Read about how to connect batteries correctly.

Electrolytic capacitors (electrolytes) are suitable for any with a nominal capacity of 10 ... 100 microfarads and an operating voltage of 6.3 volts. For reliability, it is better to choose capacitors for a higher operating voltage - 10 .... 16 volts. Recall that the operating voltage of electrolytes should be slightly higher than the supply voltage of the circuit.

You can take electrolytes with a larger capacity, but the dimensions of the device will increase markedly. When connecting capacitors to the circuit, observe the polarity! Electrolytes do not like polarity reversals.

All circuits have been tested and are working. If something does not work, then first of all we check the quality of soldering or connections (if assembled on a breadboard). Before soldering parts into the circuit, they should be checked with a multimeter, so that later you won’t be surprised: “Why doesn’t it work?”

LEDs can be anything. You can use both conventional 3-volt indicator lights and bright ones. Bright LEDs have a transparent body and have a greater light output. For example, bright red LEDs with a diameter of 10 mm look very impressive. Depending on the desire, LEDs of other emission colors can be used: blue, green, yellow, etc.

:: HOW TO MAKE A FLASHER::. Do-it-yourself flasher for 220 volts

Scheme of a powerful flasher

Scheme of a powerful flasher It was required, in exchange for an unusable mechanical relay, powerful enough, to build a similar in size, but already electronic. Since over time, the relay contacts burn out and the device stops working. The only problem in the process of alteration was such that the relay must stand in the break of the positive wire, and withstand significant power. But the use of a more powerful transistor, such as KT819, also did not lead to the desired result. Too much heat was generated by the transistor when switching 50 watts. There was only one salvation - the use of a radiator, but due to the limited space, the idea disappeared by itself. It was decided to use a field effect transistor as a key. To do this, I had to slightly modify the circuit and add a resistor R4, due to the fact that the transistor has a large input resistance of the isolated N-channel. This resistor is selected up or down, visually controlling the clear switching of the lamps. See diagram and description here

elwo.ru

Immediately, I will make a reservation, the idea is not mine, it was taken from the site chipdip.ru. This is a simple flasher with 6 LEDs, a feature of which is the complete absence of additional active control elements (transistors, microcircuits).

The basis of the device is a flashing red LED HL3 in series, with which two ordinary red LEDs HL1 and HL2 are connected. When the blinking LED HL3 flashes, the LEDs HL1 and HL2 light up along with it.

This opens the diode VD1, which shunts the green LEDs HL4-HL6, which go out.

When the flashing HL3 LED goes out, the HL1 and HL2 LEDs go out with it, while the group of green LEDs HL4-HL6 lights up.

Then the whole cycle is repeated. In more detail you can see about the flasher on this video:

Simple flasher

The device is powered by a Krona-type battery with a voltage of 9 V. Resistors of the MLT-0.125 type, R1 100 Ohm, R2 300 Ohm. In the original source, a VD1 diode of the KD522 type was used, it was replaced by the D220. LEDs can be any for a voltage of 2.5-3 V, and a current of 10-30 mA. Sincerely, Lekomtsev D. G.

samodelnie.ru

THREE-PHASE MULTIVIBRATOR

Recently, a circuit of a very interesting multivibrator was found on the Internet. This multivibrator is not ordinary, but for three channels. As a rule, the electric circuit of a multivibrator is built on two transistors, and it is designed to receive rectangular pulses.

A multivibrator is a very simple device that serves as the basis for generating pulses. He found wide application in amateur radio circles. A novice radio amateur, after mastering the theoretical part of electronics, proceeds from theory to business. The very first design of beginners is a flasher with two LEDs, and the basis of such a flasher is a multivibrator.

The multivibrator under consideration has three channels that open in turn. All editing was done on a prototyping board, moreover, with significant scatter. The circuit uses low-power transistors KT315, you can also use more powerful domestic transistors, for example KT815, KT817 and even KT819. The choice is very large, you can use literally any transistors of direct or reverse conduction,

I personally soldered the circuit at 3 a.m., so it worked the third time, I always confused the connection of electrolytic capacitors (it was apparently not worth working so late), then I burned 2 transistors, I had to go to the pantry for new ones ...

In order not to repeat my mistakes, you should carefully check the entire installation, special attention should be paid to the connection of electrolytic capacitors. The supply voltage is selected in the region of 4 ... 6 volts, although 9V from the "crown" works well.

It is advisable to choose multi-colored LEDs with the same parameters. Literally any low power LEDs can be used.

I don’t know where such a multivibrator can be used except for flashing lights and garlands (can you invent a three-stroke converter with such a generator?). But at least it will be a great electronic New Year's toy for your child or younger brother :) I assembled and tested the circuit - AKA KASYAN.

Circuit Engineering Forum for Beginners

Discuss the article THREE-PHASE MULTIVIBRATOR

radioskot.ru

From 220 volts. The circuit can be used as an indicator of mains voltage.

In the blinking LED circuit, (DIAC) is used. The dinistor is typically used as a pulse generator to drive a thyristor or triac. When a voltage below the breakdown voltage is applied to the dinistor, it does not pass current through itself (in fact, an open circuit is obtained) and only a very small current passes through it.

But if the voltage rises to the breakdown threshold, then this puts the dinistor into a state of electrical conductivity. For a DB3 dinistor, the breakdown voltage is about 35 volts. The DB3 dinistor conducts current in both directions. Diode VD1 rectifies the alternating voltage of the network. Resistor R1 is designed to limit the current flowing through the dinistor DB3.

When power is applied to the circuit, it does not light. C1 starts charging through diode VD1 and resistor R1. When the capacitor C1 is charged to a voltage of about 35 volts, the dinistor breaks down, the current begins to flow through it, causing the LED to light up. Resistor R2 limits the current through the LED to a safe value of 30 mA.

When DB3 passes a current through itself, at this time the capacitor C1 is discharged, the voltage across it drops below the breakdown voltage of the dinistor, as a result of which the latter closes and the LED goes out. Then everything repeats again. And as a result, the LED starts flashing periodically.

The flash frequency of the LED is determined by the capacitance of the capacitor C1. A higher value gives a low flash rate and vice versa. If the dinistor does not open, then the resistance R1 can be reduced to 10 kOhm, but the power R1 in this case must be at least 5 watts.

Second option flashing LED from 220 volts. Here, the alternating mains voltage of 220 volts is reduced to 50 volts, due to the quenching capacitor C1, and is rectified by the diode bridge VD1-VD4. Resistor R1 is designed to protect the capacitor from inrush current and discharge it after disconnecting the circuit from the network.

The main element of the circuit is the DB3 dinistor. The dinistor together with capacitor C2 forms a relaxation oscillator. When voltage is applied, capacitor C2 begins to slowly charge through resistor R3. When the capacitor reaches a voltage equal to the breakdown voltage of the dinistor (approximately 35V), the dinistor begins to conduct current, including the LED. Next, the capacitor C2 is discharged and the dinistor closes, the LED goes out. And the cycle repeats again. With the specified capacitance of capacitor C2, the frequency of LED flashes is approximately 1 time per second.

Attention: both circuits are directly connected to the 220 volt power supply and do not have galvanic isolation. Be extremely careful when assembling and operating this device.