Flashing LEDs are often used in various signal circuits. Light emitting diodes (LEDs) of various colors have been on sale for quite a long time, which blink periodically when connected to a power source. No additional parts are needed to make them blink. A miniature integrated circuit that controls its operation is mounted inside such an LED. However, for a novice radio amateur it is much more interesting to make a flashing LED with your own hands, and at the same time study the principle of operation of an electronic circuit, in particular flashers, and master the skills of working with a soldering iron.

How to make an LED flasher with your own hands

There are many schemes that can be used to make an LED blink. Flashing devices can be made either from individual radio components or based on various microcircuits. First, we will look at the multivibrator flasher circuit using two transistors. The most common parts are suitable for its assembly. They can be purchased at a radio parts store or “obtained” from obsolete televisions, radios and other radio equipment. Also in many online stores you can buy kits of parts for assembling similar circuits of LED flashers.

The figure shows a multivibrator flasher circuit consisting of only nine parts. To assemble it you will need:

• two resistors of 6.8 – 15 kOhm;
• two resistors with a resistance of 470 - 680 Ohms;
• two low-power transistors with an n-p-n structure, for example KT315 B;
• two electrolytic capacitors with a capacity of 47–100 μF
• one low-power LED of any color, for example red.

It is not necessary that paired parts, for example resistors R2 and R3, have the same value. A small spread in values ​​has virtually no effect on the operation of the multivibrator. Also, this LED flasher circuit is not critical to the supply voltage. It works confidently in the voltage range from 3 to 12 volts.

The multivibrator flasher circuit works as follows. At the moment of supplying power to the circuit, one of the transistors will always be open a little more than the other. The reason could be, for example, a slightly higher current transfer coefficient. Let transistor T2 initially open more. Then the charging current of capacitor C1 will flow through its base and resistor R1. Transistor T2 will be in the open state and its collector current will flow through R4. There will be a low voltage on the positive plate of capacitor C2, connected to the collector T2, and it will not charge. As C1 charges, the base current T2 will decrease and the collector voltage will increase. At some point, this voltage will become such that a charging current for capacitor C2 will flow and transistor T3 will begin to open. C1 will begin to discharge through transistor T3 and resistor R2. The voltage drop across R2 will reliably close T2. At this time, current will flow through the open transistor T3 and resistor R1 and LED1 will light up. In the future, the charge-discharge cycles of the capacitors will be repeated alternately.

If you look at the oscillograms on the collectors of the transistors, they will look like rectangular pulses.

When the width (duration) of rectangular pulses is equal to the distance between them, then the signal is said to have a meander shape. By taking oscillograms from the collectors of both transistors at the same time, you can see that they are always in antiphase. The duration of the pulses and the time between their repetitions directly depend on the products R2C2 and R3C1. By changing the ratio of products, you can change the duration and frequency of LED flashes.

To assemble the blinking LED circuit, you will need a soldering iron, solder and flux. As a flux, you can use rosin or liquid soldering flux, sold in stores. Before assembling the structure, it is necessary to thoroughly clean and tin the terminals of the radio components. The terminals of the transistors and the LED must be connected in accordance with their purpose. It is also necessary to observe the polarity of connection of electrolytic capacitors. The markings and pin assignments of KT315 transistors are shown in the photo.

Flashing LED on one battery

Most LEDs operate at voltages above 1.5 volts. Therefore, they cannot be lit in a simple way from one AA battery. However, there are LED flasher circuits that allow you to overcome this difficulty. One of these is shown below.

In the LED flasher circuit there are two chains of capacitor charging: R1C1R2 and R3C2R2. The charging time of capacitor C1 is much longer than the charging time of capacitor C2. After charging C1, both transistors open and capacitor C2 is connected in series with the battery. Through transistor T2, the total voltage of the battery and capacitor is applied to the LED. The LED lights up. After capacitors C1 and C2 are discharged, the transistors close and a new capacitor charging cycle begins. This LED flasher circuit is called a voltage boost circuit.

We looked at several LED flashing light circuits. By assembling these and other devices, you can not only learn how to solder and read electronic circuits. As a result, you can get fully functional devices useful in everyday life. The matter is limited only by the imagination of the creator. With some ingenuity, you can, for example, make an LED flasher into a refrigerator door open alarm or a bicycle turn signal. Make the eyes of a soft toy blink.

This design, or rather its diagram, can be called simple and accessible. The device operates on the basis of the KR1006VI1 timer, which has two precision comparators. In addition, the device includes a timing oxide capacitor C1, a voltage divider across resistances R1 and R2. From the third output of the DA1 chip, control pulses follow to the LEDs HL1-HL3.

The circuit is turned on using toggle switch SB1. At the initial moment of time, the output of the timer has a high voltage level and the LEDs light up. Capacity C1 begins to charge through the circuit R1 R2. After one second, the time can be adjusted by resistances R1 R2 and capacitor C1, the voltage on the capacitor plates reaches the response value of one of the comparators. In this case, the voltage at pin three DA1 will be zero, the LEDs will go out. This continues from cycle to cycle as long as voltage is applied to the amateur radio structure.

It is recommended to use high-power LEDs HPWS-T400 or similar ones with a current consumption of no higher than 80 mA in the design. You can also use one LED, for example LXHL-DL-01, LXHL-FL1C, LXYL-PL-01, LXHL-ML1D, LXHL-PH01.

Finding various objects or, for example, pets in the dark will become easier if you attach our amateur radio development to them, which will automatically turn on when darkness falls and begin to emit a light signal.

This is a regular asymmetrical multivibrator based on bipolar transistors of different conductivity VT2, VT3, which generates short pulses with an interval of a couple of seconds. The light source is a powerful LED HL1, the light sensor is a phototransistor.

A phototransistor with resistances R1, R2 forms a voltage divider in the base circuit of transistor VT2. During daylight hours, the voltage at the emitter junction of transistor VT2 is low, and it is locked together with its colleague VT3. With the onset of darkness, the transistors begin to operate in the mode of generating pulses from which the LED flashes

Flashing beacons are used in electronic home security systems and on cars as indication, signaling and warning devices. Moreover, their appearance and “filling” are often not at all different from flashing lights (special signals) of emergency and operational services.

There are classic beacons on sale, but their internal “filling” is striking in its anachronism: they are made on the basis of powerful lamps with a rotating cartridge (a classic of the genre) or lamps such as IFK-120, IFKM-120 with a stroboscopic device that provides flashes at regular intervals ( pulse beacons). Meanwhile, this is the 21st century, when there is a triumphal march of very bright (powerful in terms of luminous flux) LEDs.

One of the fundamental points in favor of replacing incandescent and halogen lamps with LEDs, in particular in flashing beacons, is the longer service life (uptime) and lower cost of the latter.

The LED crystal is practically indestructible, so the service life of the device mainly determines the durability of the optical element. The vast majority of manufacturers use various combinations of epoxy resins for its production, of course, with varying degrees of purification. In particular, because of this, LEDs have a limited resource, after which they become cloudy.

Various manufacturers (we won’t advertise them for free) claim a lifespan of their LEDs from 20 to 100 thousand (!) hours. I have a hard time believing the last figure, because the LED should work continuously for 12 years. During this time, even the paper on which the article is printed will turn yellow.

However, in any case, compared to the resource of traditional incandescent lamps (less than 1000 hours) and gas-discharge lamps (up to 5000 hours), LEDs are several orders of magnitude more durable. It is quite obvious that the key to a long resource is to ensure favorable thermal conditions and stable power supply to the LEDs.

The predominance of LEDs with a powerful luminous flux of 20 - 100 lm (lumens) in the latest industrial electronic devices, in which they work instead of incandescent lamps, gives radio amateurs the basis to use such LEDs in their designs. Thus, I bring the reader to the idea of ​​​​the possibility of replacing various lamps in emergency and special beacons with powerful LEDs. In this case, the current consumption of the device from the power source will decrease and will depend mainly on the LED used. For use in a car (as a special signal, emergency warning light, and even a “warning triangle” on the roads), current consumption is not important, since the car’s battery has a fairly large energy capacity (55 or more Ah or more). If the beacon is powered from an autonomous source, then the current consumption of the equipment installed inside will be of no small importance. By the way, a car battery without recharging can be discharged if the beacon is used for a long time.

So, for example, a “classic” beacon for operational and emergency services (blue, red, orange, respectively), when powered by a 12 V DC source, consumes a current of more than 2.2 A, which is the sum of that consumed by the electric motor (rotating the socket) and the lamp itself. When a flashing pulse beacon is operating, the current consumption is reduced to 0.9 A. If, instead of a pulse circuit, you assemble an LED circuit (more on this below), the consumption current will be reduced to 300 mA (depending on the power of the LEDs used). Savings in parts costs are also noticeable.

Of course, the question of the strength of light (or, better said, its intensity) from certain flashing devices has not been studied, since the author did not have and does not have special equipment (lux meter) for such a test. But due to the innovative solutions proposed below, this issue becomes secondary. After all, even relatively weak light pulses (in particular from LEDs) passed through the prism of the non-uniform glass of the beacon cap at night are more than sufficient for the beacon to be noticed several hundred meters away. That's the point of long-range warning, isn't it?

Now let’s look at the electrical circuit of the “lamp substitute” of the flashing light (Fig. 1).

This multivibrator electrical circuit can rightfully be called simple and accessible. The device is developed on the basis of the popular integrated timer KR1006VI1, containing two precision comparators that provide a voltage comparison error of no worse than ±1%. The timer has been repeatedly used by radio amateurs to build such popular circuits and devices as time relays, multivibrators, converters, alarms, voltage comparison devices and others.

The device, in addition to the integrated timer DA1 (multifunctional microcircuit KR1006VI1), also includes a time-setting oxide capacitor C1 and a voltage divider R1R2. C3 of the output of the DA1 microcircuit (current up to 250 mA), control pulses are sent to the LEDs HL1-HL3.

How the device works

The beacon is turned on using switch SB1. The operating principle of a multivibrator is described in detail in the literature.

At the first moment, there is a high voltage level at pin 3 of the DA1 chip - and the LEDs light up. The oxide capacitor C1 begins to charge through the circuit R1R2.

After about one second (the time depends on the resistance of the voltage divider R1R2 and the capacitance of capacitor C1, the voltage on the plates of this capacitor reaches the value necessary to trigger one of the comparators in the single housing of the DA1 microcircuit. In this case, the voltage at pin 3 of the DA1 microcircuit is set equal to zero - and the LEDs go out. This continues cyclically as long as the device is supplied with power.

In addition to those indicated in the diagram, I recommend using high-power HPWS-T400 or similar LEDs with a current consumption of up to 80 mA as HL1-HL3. You can use only one LED from the series LXHL-DL-01, LXHL-FL1C, LXYL-PL-01, LXHL-ML1D, LXHL-PH01,

LXHL-MH1D manufactured by Lumileds Lighting (all orange and red-orange glow colors).

The supply voltage of the device can be increased to 14.5 V, then it can be connected to the on-board vehicle network even when the engine (or rather, the generator) is running.

Design Features

A board with three LEDs is installed in the housing of the flashing light instead of the “heavy” standard design (lamp with a rotating socket and electric motor).

In order for the output stage to have even more power, you will need to install a current amplifier on transistor VT1 at point A (Fig. 1), as shown in Fig. 2.

After such modification, you can use three parallel-connected LEDs of the types LXHL-PL09, LXHL-LL3C (1400 mA),

UE-HR803RO (700 mA), LY-W57B (400 mA) - all orange. In this case, the total current consumption will increase accordingly.

Option with flash lamp

Those who have preserved parts of cameras with a built-in flash can go the other way. To do this, the old flash lamp is dismantled and connected to the circuit as shown in Figure 3. Using the presented converter, also connected to point A (Figure 1), pulses with an amplitude of 200 V are received at the output of the device with a low supply voltage. Supply voltage in this case it is definitely increased to 12 V.

Electronic tricks for inquisitive children Andrey Petrovich Kashkarov

3.17. Flashing light: do it yourself

Answer

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This circuit can be used to indicate an alarm. The homemade product is connected to a stabilized power source with a voltage of 12 V. Such a source can be a power supply with an adjustable output voltage, purchased on the radio market. The power supply is called stabilized because it contains a stabilizer that keeps the output voltage at a certain level.

The circuit is as simple as possible, it contains only 4 parts: a transistor KT315 of the p-p-n structure, a 1.5 kOhm resistor, an electrolytic capacitor of 470 μF and a voltage of at least 16 V (the capacitor voltage should always be an order of magnitude greater than the homemade supply voltage) and LED (in our case, red). To connect the parts correctly, you need to know their pinout (pinout). The pinout of the transistor and LED of this design is shown in Fig. 5.2. Transistors of the KT315 series are the same in appearance as KT361. The only difference is the placement of the letter. For the former, the letter is placed on the side, for the latter - in the middle.

Now, using a soldering iron and wires, let's try to assemble our device. In Fig. Figure 5.3 shows how you should connect the parts together. Blue lines are wires, thick black dots are solder points. This type of installation is called wall-mounted; there is also mounting on printed circuit boards.

Rice. 5.2. - Pinout:
a) transistor KT315B
b) LED AL307B

Rice. 5.3. - Appearance of the assembled device
Check that the parts are connected correctly and connect the device to the power supply. A miracle happened - the LED began to flash brightly. Your first homemade product has worked!!!