A simple 220 volt flasher. Flasher on an incandescent lamp. Flashing LED on one battery

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

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

Here is a schematic diagram of one of the simplest flashing lights. The basic basis of this circuit is a symmetrical multivibrator. The flasher is assembled from readily available and inexpensive parts, many of which can be found in old radio equipment and reused. The parameters of 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 transistors VT1 and VT2 open alternately. In the open state, the E-K junction of transistors passes current. Since LEDs are included in the collector circuits of the transistors, they glow when current passes through them.

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

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

It is advisable not only to repeat this scheme, but also to “play around” with it. You can, for example, increase the capacity of capacitors C1, C2. At the same time, 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 μF (47 μF) and R2 = R3 = 27 kOhm (kΩ), the frequency will be about 0.5 Hz (Hz). Thus, the LEDs will switch 1 time within 2 seconds. By reducing the capacitance of 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 μF, then the LEDs will switch with a frequency of about 26 Hz, which will be almost invisible to the eye - both LEDs will simply glow.

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

The blinking frequency of the LEDs can be changed more smoothly 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 variable resistor knob. 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 values ​​of the remaining parts the same (see table below).

This is what a flasher looks like with continuously adjustable LED flash frequency on a breadboard.

Initially, it is better to assemble the flasher circuit on a solderless breadboard and configure the operation of the circuit as desired. A solderless breadboard is generally very convenient for carrying out all sorts of experiments with electronics.

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

Name	Designation	Rating/Parameters	Brand or item type
Transistors	VT1, VT2		KT315 with any letter index
Electrolytic capacitors	C1, C2	10...100 µF (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 3 volt

It is worth noting that the KT315 transistors have a complementary “twin” - the KT361 transistor. Their cases are very similar and can be easily confused. It wouldn’t be very scary, but these transistors have different structures: KT315 - n-p-n, and KT361 – p-n-p. That's why they are called complementary. If instead of the KT315 transistor you install KT361 in the circuit, it will not work.

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

The photo shows the transistor KT361 (left) and KT315 (right). On the transistor body, only a letter index is usually indicated. Therefore, it is almost impossible to distinguish KT315 from KT361 by appearance. To reliably make sure that it is KT315 and not KT361 that is in front of you, it is 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. Old electrolytic capacitors especially require checking. They have one problem - loss of capacity. Therefore, it would be a good idea to check the capacitors.

By the way, using a flasher you can indirectly estimate the capacitance of capacitors. If the electrolyte has “dried up” and lost part of its capacity, then the multivibrator will operate in asymmetrical mode - this will immediately become noticeable purely visually. This means that one of the capacitors C1 or C2 has less capacitance ("dried") 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 from 3 AA or AAA batteries (1.5 V * 3 = 4.5 V). Read about how to connect batteries correctly.

Any electrolytic capacitors (electrolytes) with a nominal capacity of 10...100 μF and an operating voltage of 6.3 volts are suitable. For reliability, it is better to choose capacitors for a higher operating voltage - 10....16 volts. Let us remember that the operating voltage of the 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 noticeably. When connecting capacitors to the circuit, observe polarity! Electrolytes do not like polarity reversal.

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

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

It is recommended to start discovering the world of radio electronics, full of mysteries, without specialized education, by assembling simple electronic circuits. The level of satisfaction will be higher if the positive result is accompanied by a pleasant visual effect. The ideal option is circuits with one or two flashing LEDs in the load. Below is information that will help in implementing the simplest DIY schemes.

Ready-made flashing LEDs and circuits using them

Among the variety of ready-made flashing LEDs, the most common are products in a 5 mm housing. In addition to ready-made single-color flashing LEDs, there are two-terminal versions with two or three crystals of different colors. They have a built-in generator in the same housing with the crystals, which operates at a certain frequency. It issues single alternating pulses to each crystal according to a given program. The blinking speed (frequency) depends on the set program. When two crystals glow simultaneously, the flashing LED produces an intermediate color. The second most popular are flashing light-emitting diodes controlled by current (potential level). That is, to make a LED of this type blink, you need to change the power supply at the corresponding pins. For example, the emission color of a two-color red-green LED with two terminals depends on the direction of current flow.

A three-color (RGB) four-pin flashing LED has a common anode (cathode) and three pins for controlling each color separately. The flashing effect is achieved by connecting to an appropriate control system.

It’s quite easy to make a flasher based on a ready-made flashing LED. To do this, you will need a CR2032 or CR2025 battery and a 150–240 Ohm resistor, which should be soldered to any pin. Observing the polarity of the LED, the contacts are connected to the battery. The LED flasher is ready, you can enjoy the visual effect. If you use a Krona battery, based on Ohm's law, you should select a resistor of higher resistance.

Conventional LEDs and flasher systems based on them

A novice radio amateur can assemble a flasher using a simple one-color light-emitting diode, having a minimum set of radio elements. To do this, we will consider several practical schemes, characterized by a minimum set of radio components used, simplicity, durability and reliability.

The first circuit consists of a low-power transistor Q1 (KT315, KT3102 or a similar imported analogue), a 16V polar capacitor C1 with a capacity of 470 μF, a resistor R1 of 820-1000 ohms and an LED L1 like AL307. The entire circuit is powered by a 12V voltage source.

The above circuit works on the principle of avalanche breakdown, so the base of the transistor remains “hanging in the air”, and a positive potential is applied to the emitter. When turned on, the capacitor is charged to approximately 10V, after which the transistor opens for a moment and releases the accumulated energy to the load, which manifests itself in the form of LED blinking. The disadvantage of the circuit is the need for a 12V voltage source.

The second circuit is assembled on the principle of a transistor multivibrator and is considered more reliable. To implement it you will need:

• two KT3102 transistors (or their equivalent);
• two 16V polar capacitors with a capacity of 10 µF;
• two resistors (R1 and R4) of 300 Ohms each to limit the load current;
• two resistors (R2 and R3) of 27 kOhm each to set the base current of the transistor;
• two LEDs of any color.

In this case, a constant voltage of 5V is supplied to the elements. The circuit operates on the principle of alternate charge-discharge of capacitors C1 and C2, which leads to the opening of the corresponding transistor. While VT1 discharges the accumulated energy of C1 through the open collector-emitter junction, the first LED lights up. At this time, a smooth charge of C2 occurs, which helps to reduce the base current VT1. At a certain moment, VT1 closes, and VT2 opens and the second LED lights up.

The second scheme has several advantages:

1. It can operate in a wide voltage range starting from 3V. When applying more than 5V to the input, you will have to recalculate the resistor values ​​so as not to break through the LED and not exceed the maximum base current of the transistor.
2. You can connect 2–3 LEDs to the load in parallel or in series by recalculating the resistor values.
3. An equal increase in the capacitance of the capacitors leads to an increase in the duration of the glow.
4. By changing the capacitance of one capacitor, we get an asymmetrical multivibrator in which the glow time will be different.

In both options, you can use pnp transistors, but with correction of the connection diagram.

Sometimes, instead of flashing LEDs, a radio amateur observes a normal glow, that is, both transistors are partially open. In this case, you need to either replace the transistors or solder resistors R2 and R3 with a lower value, thereby increasing the base current.

It should be remembered that 3V power will not be enough to light an LED with a high forward voltage value. For example, a white, blue or green LED will require more voltage.

In addition to the considered circuit diagrams, there are a great many other simple solutions that cause the LED to blink. Beginning radio amateurs should pay attention to the inexpensive and widespread NE555 microcircuit, which can also implement this effect. Its versatility will help you assemble other interesting circuits.

Application area

Flashing LEDs with a built-in generator have found application in the construction of New Year's garlands. By assembling them in a series circuit and installing resistors with slight differences in value, they achieve a shift in the blinking of each individual element of the circuit. The result is an excellent lighting effect that does not require a complex control unit. It is enough just to connect the garland through a diode bridge.

Flashing light-emitting diodes, controlled by current, are used as indicators in electronic technology, when each color corresponds to a certain state (on/off charge level, etc.). They are also used to assemble electronic displays, advertising signs, children's toys and other products in which multi-colored flashing arouses people's interest.

The ability to assemble simple flashing lights will become an incentive to build circuits using more powerful transistors. With a little effort, you can use flashing LEDs to create many interesting effects, such as a traveling wave.

Read also

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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.

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.

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.