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 reversals.
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.
Flashing beacons are used in electronic security systems and on vehicles as indication, signaling and warning devices. Moreover, their appearance and “filling” are often not at all different from the flashing lights of emergency and operational services (special signals) - see fig. 3.9.
The internal “filling” of classic lamps is striking in its anachronism: here and there, beacons based on 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 regularly appear on sale time (pulse beacons). Meanwhile, this is the 21st century, in which the triumphant march of super-bright (and powerful in terms of luminous flux) LEDs continues.
One of the fundamental points in favor of replacing incandescent and halogen lamps with LEDs, in particular in flashing lights, is the resource and cost of the LED.
By resource, as a rule, we mean failure-free service life.
The resource of an LED is determined by two components: the resource of the crystal itself and the resource of the optical system. The vast majority of LED manufacturers use various combinations of epoxy resins for the optical system, of course, with varying degrees of purification. In particular, because of this, LEDs have a limited resource in this part of the parameters, after which they “go cloudy”.
Various manufacturing companies (we won’t advertise them for free) claim a lifespan of their products in terms of LEDs from 20 to 100 thousand (!) hours. I categorically disagree with the last figure, since I have little faith that a separately selected LED will work continuously for 12 years. During this time, even the paper on which my book is printed will turn yellow.
However, it is quite obvious that the key to a long resource is ensuring the thermal conditions and power conditions of the LEDs.
In any case, compared to the life of traditional incandescent lamps (less than 1000 hours) and gas-discharge lamps (up to 5000 hours), LEDs are several orders of magnitude more durable.
The predominance of LEDs with a powerful luminous flux of 20-100 lm (lumens) in the latest industrial electronic devices, where they even replace incandescent lamps, gives radio amateurs a reason to use such LEDs in their designs.
Figure 3.9. Appearance of flashing lights
Thus, I am talking about replacing lamps for various purposes with powerful LEDs in emergency and special beacons. Moreover, with such a replacement, the main current consumption from the power source will decrease and will depend mainly on the current consumption of the LED used. For use in conjunction with a car (as a special signal, emergency light indicator and even a “warning triangle” on the roads), current consumption is not important, since the car battery has a fairly large energy capacity (55 A/h or more). If the beacon is powered by another power source (autonomous or stationary), then the dependence of the current consumption on the equipment installed inside is direct. By the way, the car battery can also discharge if the beacon is used for a long time without recharging the battery.
So, for example, a “classic” beacon for operational and emergency services (blue, red, orange, respectively) with a 12 V power supply consumes a current of more than 2.2 A. This current consists of taking into account the consumption of the electric motor of the rotating socket and the current consumption of 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 powerful LEDs used). The savings in detail are obvious.
The above data was established by practical experiments conducted by the author in May 2009 in St. Petersburg (a total of 6 different classic flashing lights were tested).
Of course, the question of the strength or, better yet, intensity of light from certain flashing devices has not been studied, since the author does not have special equipment (lux meter) for such a test. But due to the innovative solutions proposed below, this issue remains of secondary importance. After all, even relatively weak light pulses (in particular, from powerful LEDs) at night and in the dark 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. 3.10).
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 2 precision comparators that provide an error in voltage comparison 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, etc.
The device includes, in addition to the integrated timer DA1 (multifunctional microcircuit KR1006VI1), a timing oxide capacitor C1, and a voltage divider R1R2. From the output of the DA1 chip (current up to 250 mA), control pulses are sent to the HL1-HL3 LEDs.
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 of time, there is a high voltage level at pin 3 of the DA1 chip and the LEDs are lit. The oxide capacitor C1 begins to charge through the circuit R1R2.
After about 1 sec. (the time depends on the resistance of the voltage divider R1R2 and the capacitance of the 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 chip is set equal to zero, and the LEDs go out. This continues cyclically as long as the supply voltage is applied to the device.
Rice. 3.10. Simple electrical circuit of an LED beacon
In addition to those indicated in the diagram, I recommend using high-power LEDs HPWS-TH00 or similar ones with a current consumption of up to 80 mA as HL1-HL3. Only one LED from the LXHL-DL-01, LXHL-FL1C, LXYL-PL-01, LXHL-ML1D, LXHL-PH01, LXHL-MH1D series manufactured by Lumileds Lighting can be used (all orange and red-orange).
The device supply voltage can be adjusted to 12 V.
The board with the elements of the device is installed in the housing of the flashing light instead of the “heavy” standard design with a lamp and a rotating socket with an electric motor. A view of the installed board with 3 LEDs is shown in Fig. 3.11.
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. 3.10), as shown in Fig. 3.12.
After this modification, you can use three parallel-connected LEDs of the types LXHL-PL09, LXHL-LL3C (1400 mA), UE-lf R803RQ (700 mL), LY-W57B (400 mA) - all orange.
If there is no power, the device does not consume any current at all.
Rice. 3 11 View of the LED beacon board installed in the standard flashing beacon housing
Those who still have 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 Fig. 3.13.
Using the presented converter, which is also connected to point A (Fig. 3.10), pulses with an amplitude of 200 V are received at the output of the device with a low supply voltage. The supply voltage in this case is increased to 12 V.
The output pulse voltage can be increased by connecting several zener diodes into the circuit, following the example of VD1, VD2 (Fig. 3.13). These are silicon planar zener diodes designed to stabilize voltage in DC circuits with a minimum current of 1 mA and a power of up to 1 W. Instead of those indicated in the diagram, you can use KS591A zener diodes.
Elements C1, R3 form a damping RC circuit that dampens high-frequency vibrations.
Now, with the appearance (in time) of pulses at point A (Fig. 3.10), the ELI flash lamp will turn on. Built into the body of the flashing light, this design will allow it to continue to be used if the standard beacon fails.
Fig 3.12 Connection diagram for additional amplifier stage
Option with flash lamp
Figure 3 13. Flash lamp connection diagram
Unfortunately, the life of a flash lamp from a portable camera is limited and is unlikely to exceed 50 hours. continuous operation in pulse mode. Battery charging and discharging control device for a miner's flashlight
Often, the mobile lighting devices we purchase, which use the energy of the built-in rechargeable battery, but are not equipped with an indicator of its status, fail us at the most inopportune moment. In this article, the author proposes a simple device…….
One of the simplest circuits in amateur radio electronics is an LED flasher on a single transistor. Its production can be done by any beginner who has a minimum soldering kit and half an hour of time.
Although the circuit under consideration is simple, it allows you to clearly see the avalanche breakdown of the transistor, as well as the operation of the electrolytic capacitor. Including, by selecting the capacitance, you can easily change the blinking frequency of the LED. You can also experiment with the input voltage (in small ranges), which also affects the operation of the product.
Design and principle of operation
The flasher consists of the following elements:- power supply;
- resistance;
- capacitor;
- transistor;
- Light-emitting diode.
The capacitor is located in the circuit before the closed transistor, therefore it accumulates electrical energy. This happens until the voltage at its terminals reaches a value sufficient to ensure the so-called avalanche breakdown.
In the second phase of the cycle, the energy accumulated in the capacitor “breaks through” the transistor, and current passes through the LED. It flashes for a short time and then goes out again as the transistor turns off again.
Then the flasher operates in cyclic mode and all processes are repeated.
Necessary materials and radio components
To assemble an LED flasher with your own hands, powered by a 12 V power source, you will need the following:- soldering iron;
- rosin;
- solder;
- 1 kOhm resistor;
- capacitor with a capacity of 470-1000 μF at 16 V;
- transistor KT315 or its more modern analogue;
- classic LED;
- simple wire;
- 12V power supply;
- matchbox (optional).
The last component acts as a housing, although the circuit can be assembled without it. Alternatively, a circuit board can be used. The mounted mounting described below is recommended for beginner radio amateurs. This assembly method allows you to quickly navigate the circuit and do everything right the first time.
Flasher assembly sequence
The production of a 12 V LED flasher is carried out in the following sequence. The first step is to prepare all the above components, materials and tools.For convenience, it is better to immediately fix the LED and power wires to the case. Next, a resistor should be soldered to the “+” terminal.
The free resistance leg is connected to the emitter of the transistor. If KT315 is placed with the marking down, then this pin will be on the far right. Next, the emitter of the transistor is connected to the positive terminal of the capacitor. You can identify it by the markings on the case - “minus” is indicated by a light stripe.
The next step is to connect the collector of the transistor to the positive terminal of the LED. KT315 has a leg in the middle. The “plus” of the LED can be determined visually. Inside the element there are two electrodes of different sizes. The one that is smaller will be positive.
Now all that remains is to solder the negative terminal of the LED to the corresponding conductor of the power supply. The negative of the capacitor is connected to the same line.
The LED flasher on one transistor is ready. By applying power to it, you can see its operation according to the principle described above.
If you want to reduce or increase the blinking frequency of the LED, you can experiment with capacitors with different capacities. The principle is very simple - the larger the element’s capacity, the less often the LED will blink.
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:
- 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.
- You can connect 2–3 LEDs to the load in parallel or in series by recalculating the resistor values.
- An equal increase in the capacitance of the capacitors leads to an increase in the duration of the glow.
- 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
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).
Rice. 1. Circuit diagram of the LED beacon
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.
Operating principle of the device
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 microcircuit - 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.
Rice. 2. Connection diagram for an additional amplifier stage
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, which is 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.
The output pulse voltage can be increased by connecting several zener diodes into the circuit following the example of VT1 (Fig. 3). These are silicon planar zener diodes designed to stabilize voltage in DC circuits with a minimum value of 1 mA and a power of up to 1 W. Instead of those indicated in the diagram, you can use KS591A zener diodes.
Rice. 3. Flash lamp connection diagram
Elements C1, R3 (Fig. 2) form a damping RC chain that dampens high-frequency vibrations.
Now, with the appearance (in time) of pulses at point A (Fig. 2), the flash lamp EL1 will turn on. This design, built into the body of the flashing light, will allow it to be used further if the standard beacon fails.
A board with LEDs installed in a standard flashing light housing
Unfortunately, the life of a flash lamp from a portable camera is limited and is unlikely to exceed 50 hours of operation in pulse mode.
See other articles section.