From the flash - a strobe and not only. Encyclopedia of radio electronics and electrical engineering

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In my opinion, those developments that do not need to be "raised from scratch" seem to be the most effective: we will talk about improving finished industrial electronic devices on our own. As a result, quite modern workable designs are obtained, one of which I bring to your attention. This is an additional node to the SEF-1 industrial flash, which was once produced in millions of "circulations".

Its basis is an IFC-120 flash lamp and a large-capacity oxide high-voltage capacitor. A transformerless voltage converter, when used from a 220V network, allows you to accumulate a charge of several hundred volts on the capacitor plates, which (when the flash is ready for use) the owner is warned by a burning neon discharge indicator on the flash body. The discharge of the capacitor occurs due to the closure of remote contacts (in the thyristor control circuit of the device) intended for connection to the camera. This is the feature I used to control the flash "from the outside".

Since in the thyristor control circuit (in the anode circuit of which the pulse transformer winding is connected) the potential difference does not exceed 10 V, I connected the output of a multivibrator on a KR1006VI1 microcircuit, assembled according to the classical scheme, to the control electrode. Now it remains only to set the required frequency of pulses, which are "transformed" into the corresponding flashes of the IFC-120 lamp.

Figure 1 shows the electrical circuit of a multivibrator on a KR1006VI1 microcircuit, switched on in self-oscillating mode, and a simple master oscillator with the ability to control the parameters of output pulses over a wide range (that is, a universal generator - with a slight modification of the output stage, it is effectively used as a high-frequency voltage converter for the SEF-1 photoflash).

Rice. 1. The electrical circuit of the multivibrator on the KR1006VI1 microcircuit, included in the self-oscillating mode

Consider the operation of a multivibrator. When power is applied to the circuit elements, capacitor C1 has a very low resistance to electric current and begins to charge through resistors R1, R2 from the power source. At the first moment, a negative pulse appears at the trigger input (pins 2 and 6 of DA1), and a high logic level voltage is set at the output of the microcircuit (pin 3). The voltage on the charging capacitor C1 grows exponentially with the time constant t=RC, where R is the sum of the resistances R1 and R2. When the voltage on the plates of the capacitor C1 reaches the level of 2/3 of the supply voltage, the internal comparator resets the microcircuit trigger to its original state, and the trigger, in turn, quickly discharges the capacitor C1 and switches the output stage to a low voltage state. Thus, the periodic charge of the capacitor C1 is carried out through the resistance circuit R1R2, and the discharge through the resistor R3. This allows you to adjust the duty cycle of the pulses over a wide range, setting the ratio between the resistances of the resistors R1 and R2.

Timing resistors R2 and R3 determine the parameters of the generator pulses and its frequency over a wide range: R2 regulates bursts of pulses (the lower its resistance, the shorter the bursts, up to single pulses), R3 regulates the pauses between pulses from 0,5 to 30 s. The parameters of the pulse repetition rate also depend on the capacitance of the capacitor C1, which can be applied up to hundreds of microfarads. In this mode, the voltage on the plates of the capacitor C1 varies from 1/4 to 2/3 of the voltage of the power source. The charge rate of the capacitor and the response threshold of the internal comparator are directly proportional to the supply voltage, so the duration of the output pulse is practically independent of the supply voltage. The output of the KR1006VI1 timer switches, sharply changing the voltage at pin 3 of DA1. Pin 5 of the microcircuit must be left free or connected to a common wire through a KM-type capacitor with a capacity of 0,1 μF. In this scheme, this is not essential.

Oxide capacitor C3 smoothes the voltage ripple from the power source. The output current of the generator on the KR1006VI1 chip (pin 3 of DA1) does not exceed 250 mA, which is quite enough for many amateur radio designs. You can connect this attachment directly to the pulse transformer of the flash. However, to control a high-voltage pulsed load, a converter with galvanic isolation is required (the circuit in Fig. 2) - it will also be required to "tame" other (except for the considered) types of flash units.

Rice. 2. Electric circuit of the output stage of the voltage converter

The conversion stage is implemented on a field-effect transistor VT1, in the source circuit of which the winding of the step-up transformer T1 of the flash is connected. For additional protection of the output stage in the circuit with a transformer, a suppressor (protective zener diode) from the KS515 series with any letter index is used. The protective zener diode must have a stabilization voltage of at least 3/4 Upit.

The microcircuit during operation can slightly heat up - up to 30 ° - 40 ° С. The battery of the device can be either self-contained (from a Krona battery with a step-up voltage converter for the operation of a flash lamp), or stationary - a power supply unit with a stabilized voltage of 6 - 15 V.

About the details. Field effect transistor VT1 can be replaced with IRF640, IRF511, IRF720. Variable resistors R2, R3 with a linear characteristic of resistance change - multi-turn, for example, SP5-1VB. Instead of an oxide capacitor C3, type K50-29 or similar is suitable. Fixed resistors - type MLT-025, non-polar capacitors - type KM.

The practical application of the combined device may be different. In addition to the first thing that comes to mind for a young man - to install it on the dance floor in the form of a stroboscope (the pulse frequency of the multivibrator in this case is selected 1 - 10 Hz), there are other options. For example, I am currently using a device for remote indication of the normal operation of the alarm system of a village house. The fact is that my farm is several kilometers away from the village. Message - forest road. But due to the fact that it is located on a hill, the estate itself can be seen from the village. But, of course, it is difficult to see if there are outsiders in it. And this is important, because most of the time I live in the city, many kilometers from the farm. But periodic bright flashes (pulse repetition rate 0,1 Hz) of the IFC-120 flash lamp, together with a reflector directed towards the nearest residential buildings, will inform you about the state of affairs when someone climbs into the house - an alarm will go off, controlled by me using a cell phone (at a distance), the flash lamp will stop blinking - this will serve as an alarm signal.

After installing and connecting the considered devices, it remains only to agree with the locals that they look in the direction of my farm. Their main task, of course, is not to detect the moment the alarm goes off (I myself will immediately detect this, as well as the local police department, which will receive calls from a cell phone installed in the estate and acting as a "remote warning"), but to trace and try to remember the identities of those "kind" people who will soon follow on foot or by car from my farm. And then it's up to law enforcement.

During the day, and even more so at night, IFC-120 flashes are clearly visible at a very long distance, which can be used in other cases when a remote signaling device is required.

Another option for using a hybrid design is the protective function of the owners of the house. The flash is located in the hallway (immediately after the front door) with a reflector to the exit, power is supplied to the device using a conventional wall switch. If the guest who enters turns out to be, to put it mildly, unwelcome, then it is easy, by pressing the switch, to act with a flash lamp turned on in the strobe mode. He will be paralyzed in actions in a non-contact way (while nothing threatens his life).

The device can be adopted not only in village houses, but also in city apartments. And there may be more extravagant options. It's all about imagination and its skillful implementation.

Author: A.Kashkarov

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