Smooth switching on of halogen incandescent lamps. How to smoothly switch on incandescent lamps and why it is needed

Any economical owner of a house or apartment strives to use electrical energy rationally, since its prices are quite high. For example, if a conventional incandescent lamp is used incorrectly, it will regularly “burn out.” Therefore, in order for it to serve you much longer, experts recommend using devices such as soft-start devices. You can also make such a block yourself using a certain scheme.

Operating principle of UPVL

With a sharp flow of electricity, the incandescent lamp wears out very quickly and the tungsten filament burns out. But if the temperature conditions of the filament and the electric current are approximately the same, then the process will be stabilized and the lamp will not burn out. In order for light sources to work as expected, you must have a special power supply.

Thanks to a special sensor, the filament will heat up to the required temperature, and the voltage level will increase to a point specified by the user. For example, up to 176 Volts. In this case, the power supply will help to significantly increase the life of the lamp.

The protection unit has one drawback - the light in the room will burn much weaker.

If the voltage is 176 V, the lighting level will decrease by about two-thirds. Therefore, experts recommend purchasing powerful lamps so that the quality of light is normal. Currently, there are special soft-start units (UPVL) for incandescent lamps, which differ in different power parameters. Therefore, before buying a unit, you need to make sure whether it can withstand large surges or voltage drops in the electrical network. Such a device must have an additional reserve, and it will be enough if the voltage in your electrical network is about 30 percent greater than the surge flow.

You need to know that the higher the standard value, the larger the dimensions of the power supply. Currently, you can purchase a power supply with a power of 150 to 1000 watts.

Types of power supplies and their characteristics

Today there are many different devices for smooth activation of LN. The most popular are:

Scheme

In order to correctly use LC soft-start units, it is necessary to use special electrical circuits. Thanks to such diagrams, you can easily understand how this device works and is designed from the inside, as well as how it should be used.

Usually, when connecting such a device, specialists use the simplest and easiest version of the circuit. Sometimes a special scheme is used with the introduction of simisters. Also, in addition to blocks of this type, you can take field-effect transistors, which operate similarly to soft-start devices.

Also, in order to control the voltage in the soft start device, you can use automatic devices.

What is a thyristor circuit?

The rectification bridge circuit (Fig. VD1, VD2, VD3, VD4) uses a light bulb (Fig. EL1) as a load and current limiter. The rectifier arms are equipped with a thyristor (Fig. VS1) and a bias circuit (Fig. R1, R2 and C1). Also, the diode bridge is installed due to the specification of the operation of the thyristor device.

After voltage is applied to the circuit, the electric current begins to flow through the filament coil and enters the bridge, and then the electrolyte is charged through a resistor. When the opening voltage limit of the thyristor is reached, it begins to open and then the current from the light bulb passes through it. As a result, the tungsten filament heats up gradually and smoothly. The period of its heating will depend on the capacity of the capacitor and resistor located in the circuit of the device.

What is remarkable about the triac

This circuit has fewer parts due to the use of a triac (Fig. VS1), which serves as a power switch.

An element such as a choke (Fig. L1), which is designed to remove various interference that appears during the opening of the power switch, can be removed from the general circuit. (Fig. R1) The resistor is a current limiter that flows to the main electrode (Fig. VS1). The circuit that sets the time is made of a resistor (Fig. R2) and a capacitance (Fig. C1), powered by a diode (Fig. VD1). This scheme works the same as the previous one. When the capacitor is charged to the level of the opening voltage of the triac, it begins to open, and then electric current flows through it and the light bulb.

In the photo below we can see a triac regulator. Such a device, in addition to adjusting the power in the load, also smoothly supplies electric current to the light bulb when it is turned on.

Scheme of operation of a block on a specialized microcircuit

The Kr1182pm1 type microcircuit was specially created by specialists to build various phase regulators.

In this case, what happens is that the microcircuit itself regulates the voltage on the source, which has a power of up to 150 watts. And if you need to control a stronger load system and dozens of lighting fixtures simultaneously, then an additional power triac is simply connected to the control circuit. In the picture below we can see how this happens.

The use of soft-start units does not end only with conventional lamps, as experts recommend using them together with halogen lamps with a power of 220 V.

It is important to know! With luminescent andLED Such units cannot be installed with lamps (LED). This is due to the fact that there are different techniques for developing circuits, as well as the principle of operation and the presence of each lighting device with its own source of measured heating for fluorescent lamps or whether there is no need for such regulation of lamps LED.

Soft start device (UPVL) for incandescent lamps 220V and 12V

Today, a large number of different UPVL models are produced, which differ in function, cost and quality. The device, which is sold in specialized stores, is connected in series to a 220 V light source. We can see the circuit and appearance of the device in the photo below.

If the power supply for the lamps is 12 or 24 V, then the device must be connected in front of the step-down transformer, also in series with the initial primary winding.

The device must correspond to the load that will be connected with a certain margin. To do this, you need to calculate the number of lamps and their total power.

Since the device is small in size, the UPVL can be placed under a chandelier, in a socket box or in a connection box.

Dimmers or dimmers

It is economically profitable and rational to use devices that create a smooth switching on of lamps, as well as provide the process of regulating their degree of brightness. Dimmers of various models can:

• Set operating programs for lighting fixtures;
• Smoothly turn lamps on and off;
• Controlled by remote control, voice commands or clapping.

When purchasing this device, you must immediately make a choice in order to know what functions are required and not buy an expensive device for a lot of money.

Before installing a dimmer, you need to decide on the method and location of lighting control. To do this, you will need to install the appropriate type of electrical wiring.

Connection diagrams can be of varying degrees of complexity. In any case, you must first turn off the voltage from a certain area.

In the figure we showed the simplest connection diagram. Here, instead of a simple switch, you can make a dimmer.

The device is connected to the gapL- wires with phase, notN- zero. Between the zero and the dimmer there is a lighting fixture. The connection to it comes out serial.

Figure (B) shows a circuit with a switch. The connection process remains the same, but here a simple switch is added. It is usually installed near the door at a certain gap between the phase and the dimmer itself. Near the bed there is a dimmer that allows you to control the lighting while lying down. When a person leaves the room, the light turns off, and when he comes back, the lamp starts up with the same brightness level.

In order to control a chandelier or other lighting fixture, you can take two dimmers, which will be located in different corners of the room (Fig. A). The two devices are connected to each other via a junction box.

Incandescent lamp control circuit: a - with two dimmers, b - with two pass-through switches and a dimmer

Thanks to this connection system, you can adjust the brightness level from different places independently of each other, but more wires will need to be installed.

Pass-through switches are used to turn on lamps from different places in the room (Fig. B). Also, you must turn on the dimmer, otherwise the lamps will not respond to the switches.

Dimmer characteristics:

• The dimmer saves electricity by only 15%, and the rest is used by the regulator.
• The devices are highly sensitive to temperature increases. Therefore, they cannot be used at temperatures above 27°C.
• The load level should not be less than 40 W, since the life of the regulator is significantly reduced.
• Dimmers should be used only for those types of devices that are recommended by the manufacturer and written in the data sheet.

Video: UPVL device

UPVLs can significantly increase the service life of halogen and incandescent lamps. These are small and inexpensive devices that can be bought at any store and installed yourself, having a specific diagram and strictly following the manufacturers' instructions.

On the Internet there are many schemes for smooth ignition and damping of LEDs powered by 12V, which you can do yourself. They all have their advantages and disadvantages and differ in the level of complexity and quality of the electronic circuit. As a rule, in most cases there is no point in building bulky boards with expensive parts. In order for the LED crystal to smoothly gain brightness at the moment of switching on and also smoothly go out at the moment of switching off, one MOS transistor with a small wiring is enough.

Scheme and principle of its operation

Let's consider one of the simplest options for a scheme for smoothly turning on and off LEDs controlled via the positive wire. In addition to ease of execution, this simplest scheme has high reliability and low cost. At the initial moment of time, when the supply voltage is applied, current begins to flow through resistor R2, and capacitor C1 is charged. The voltage across the capacitor cannot change instantly, which contributes to the smooth opening of transistor VT1. The rising gate current (pin 1) passes through R1 and leads to an increase in the positive potential at the drain of the field-effect transistor (pin 2). As a result, the LED load is switched on smoothly.

When the power is turned off, the electrical circuit breaks along the “control plus”. The capacitor begins to discharge, giving energy to resistors R3 and R1. The discharge rate is determined by the value of resistor R3. The greater its resistance, the more accumulated energy will go into the transistor, which means the longer the attenuation process will last.

To be able to adjust the time for complete switching on and off of the load, trimming resistors R4 and R5 can be added to the circuit. At the same time, for correct operation, it is recommended to use the circuit with resistors R2 and R3 of small value.
Any of the circuits can be assembled independently on a small board.

Schematic elements

The main control element is a powerful n-channel MOS transistor IRF540, the drain current of which can reach 23 A, and the drain-source voltage can reach 100V. The circuit solution under consideration does not provide for the operation of the transistor in extreme modes. Therefore, it will not need a radiator.

Instead of IRF540, you can use the domestic analogue KP540.

Resistance R2 is responsible for the smooth ignition of the LEDs. Its value should be in the range of 30–68 kOhm and is selected during the setup process based on personal preferences. Instead, you can install a compact 67 kOhm multi-turn trimmer resistor. In this case, you can adjust the ignition time using a screwdriver.

Resistance R3 is responsible for the smooth fading of the LEDs. The optimal range of its values ​​is 20–51 kOhm. Instead, you can also solder a trimmer resistor to adjust the decay time. It is advisable to solder one constant resistance of a small value in series with trimming resistors R2 and R3. They will always limit the current and prevent a short circuit if the trimming resistors are turned to zero.

Resistance R1 is used to set the gate current. For the IRF540 transistor, a nominal value of 10 kOhm is sufficient. The minimum capacitance of capacitor C1 should be 220 µF with a maximum voltage of 16 V. The capacitance can be increased to 470 µF, which will simultaneously increase the time for complete switching on and off. You can also take a capacitor for a higher voltage, but then you will have to increase the size of the printed circuit board.

Minus control

The above translated diagrams are perfect for use in a car. However, the complexity of some electrical circuits lies in the fact that some of the contacts are connected to the positive, and some to the negative (common wire or body). To control the above circuit by minus power, it needs to be slightly modified. The transistor needs to be replaced with a p-channel one, for example IRF9540N. Connect the negative terminal of the capacitor to the common point of three resistors, and connect the positive terminal to the source of VT1. The modified circuit will have power with reverse polarity, and the control positive contact will be replaced by a negative one.

Read also

Incandescent lamps are still popular due to their low price. They are widely used in auxiliary rooms where frequent light switching is required. Devices are constantly evolving, and recently a halogen lamp has been frequently used. To increase their service life and reduce energy consumption, smooth switching of incandescent lamps is used. To do this, the applied voltage must increase smoothly over a short period of time.

Smooth switching on of an incandescent lamp

A cold coil has 10 times lower electrical resistance compared to a heated coil. As a result, when a 100 W light bulb is lit, the current reaches 8 A. High brightness of the filament is not always needed. Therefore, there was a need to create soft start devices.

Operating principle

To ensure a uniform increase in the applied voltage, it is enough for the phase angle to increase in just a few seconds. The current surge is smoothed out, and the coils gradually heat up. The figure below shows one of the simplest protective circuits.

Scheme of a device for protecting against burnout of halogen and incandescent lamps on a thyristor

When turned on, the negative half-wave is supplied to the lamp through a diode (VD2), the power supply is only half the voltage. During the positive half-cycle, the capacitor (C1) is charged. When the voltage across it rises to the opening value of the thyristor (VS1), the lamp is fully supplied with mains voltage, and the start-up ends with full glow.

Diagram of a lamp burnout protection device using a triac

The circuit in the figure above operates on a triac that allows current to pass in both directions. When the lamp is turned on, negative current passes through the diode (VD1) and resistor (R1) to the control electrode of the triac. It opens and skips one half of the half-cycles. Within a few seconds, the capacitor (C1) is charged, after which the positive half-cycles open, and the lamp is fully supplied with mains voltage.

The device on the KR1182PM1 microcircuit allows you to start the lamp with a smooth increase in voltage from 5 V to 220 V.

Device diagram: starting incandescent or halogen lamps with phase control

The microcircuit (DA1) consists of two thyristors. The decoupling between the power part and the control circuit is made by a triac (VS1). The voltage in the control circuit does not exceed 12 V. The signal is supplied to its control electrode from pin 1 of the phase regulator (DA1) through a resistor (R1). The circuit starts when the contacts (SA1) open. In this case, the capacitor (C3) begins to charge. The microcircuit starts working from it, increasing the current passing to the control electrode of the triac. It begins to gradually open, increasing the voltage on the incandescent lamp (EL1). The time delay for its ignition is determined by the capacitance value of the capacitor (C3). It should not be made too large, since with frequent switching the circuit will not have time to prepare for a new start.

When you manually close the contacts (SA1), the capacitor begins to discharge into the resistor (R2) and the lamp turns off smoothly. Its switching time changes from 1 to 10 seconds with a corresponding change in capacitance (C3) from 47 μF to 470 μF. The lamp extinguishing time is determined by the resistance value (R2).

The circuit is protected from interference by a resistor (R4) and a capacitor (C4). The printed circuit board with all the parts is placed on the rear terminals of the switch and installed together with it in the box.

The lamp starts when the switch is turned off. A glow discharge lamp (HL1) is installed for illumination and voltage indication.

Soft start devices (UPVL)

There are many models available, they differ in functions, price and quality. UPVL, which can be purchased at the store, is connected in series to a 220 V lamp. The circuit and appearance are shown in the figure below. If the supply voltage of the lamps is 12 V or 24 V, the device is connected in front of the step-down transformer in series with the primary winding.

Scheme of operation of UPVL for smooth switching on of 220 V lamps

The device must match the connected load with a small margin. To do this, the number of lamps and their total power are calculated.

Due to its small dimensions, the UPVL is placed under a chandelier hood, in a socket box or in a junction box.

Device “Granite”

A special feature of the device is that it additionally protects the lamps from power surges in the home network. The characteristics of “Granite” are as follows:

• rated voltage – 175-265 V;
• temperature range – from -20 0 C to +40 0 C;
• rated power – from 150 to 3000 W.

The device is also connected in series with the lamp and switch. The device is placed together with the switch in the installation box, if its power allows. It is also installed under the chandelier cover. If the wires are connected to it directly, the protective device is installed in the distribution panel, after the circuit breaker.

Dimmers or dimmers

It is advisable to use devices that create smooth switching of lamps and also provide regulation of their brightness. Dimmer models have the following capabilities:

• setting lamp operating programs;
• smooth on and off;
• control using remote control, clap, voice.

When purchasing, you should immediately decide on your choice so as not to pay extra money for unnecessary functions.

Before installation, you need to select methods and locations for controlling the lamps. To do this, you need to make the appropriate electrical wiring.

Connection diagrams

Schemes can be of varying complexity. During any work, the voltage from the required area is first turned off.

The simplest connection diagram is shown in the figure below (a). A dimmer can be installed instead of a regular switch.

Diagram for connecting a dimmer to a lamp power supply

The device is connected to the open phase wire (L), not the neutral wire (N). There is a lamp between the neutral wire and the dimmer. The connection with it is serial.

Figure (b) shows a circuit with a switch. The connection remains the same, but a regular switch is added to it. It can be installed near the door in the gap between the phase and the dimmer. The dimmer is located near the bed with the ability to control the lighting without getting up from it. When leaving the room, the light turns off, and when returning, the lamp starts up with the previously adjusted brightness.

To control a chandelier or lamp, you can use 2 dimmers located in different places in the room (Fig. a). They are connected to each other through a junction box.

Incandescent lamp control circuit: a – with two dimmers; b – with two pass-through switches and a dimmer

This connection allows you to independently adjust the brightness from two places, but you will need more wires.

Pass-through switches are needed to turn on the light from different sides of the room (Fig. b). The dimmer must be turned on, otherwise the lamps will not respond to the switches.

Dimmer Features:

1. Energy savings using a dimmer are achieved small - no more than 15%. The rest is consumed by the regulator.
2. The devices are sensitive to increases in ambient temperature. They do not need to be used if it rises above 27 0 C.
3. The load must be at least 40 W, otherwise the life of the regulator will be reduced.
4. Dimmers are used only for those types of devices that are specified in the data sheets.

Inclusion. Video

This video will tell you how incandescent lamps turn on smoothly.

Soft start-up and shutdown devices for incandescent and halogen lamps can significantly increase their service life. It is advisable to use dimmers, which also allow you to adjust the brightness of the light.

The principle of operation of the circuit:

The control “plus” is supplied through a 1N4148 diode and a 4.7 kOhm resistor to the base of the KT503 transistor. At the same time, the transistor opens, and through it and the 68 kOhm resistor the capacitor begins to charge. The voltage on the capacitor gradually increases, and then through a 10 kOhm resistor it is supplied to the input of the field-effect transistor IRF9540. The transistor gradually opens, gradually increasing the voltage at the output of the circuit. When the control voltage is removed, the KT503 transistor closes. The capacitor is discharged to the input of the field-effect transistor IRF9540 through a 51 kOhm resistor. After the capacitor discharge process is completed, the circuit stops consuming current and goes into standby mode. The current consumption in this mode is negligible.

Circuit with control minus:

IRF9540N pinout marked

Circuit with control plus:

IRF9540N and KT503 pinout marked

This time I decided to make the circuit using the LUT method (laser ironing technology). I did this for the first time in my life, I’ll say right away that there is nothing difficult. For work we will need: a laser printer, glossy photo paper (or a page from a glossy magazine) and an iron.

COMPONENTS:

Transistor IRF9540N
Transistor KT503
Rectifier diode 1N4148
Capacitor 25V100µF
Resistors:
- R1: 4.7 kOhm 0.25 W
- R2: 68 kOhm 0.25 W
- R3: 51 kOhm 0.25 W
- R4: 10 kOhm 0.25 W
Single-sided fiberglass and ferric chloride
Screw terminal blocks, 2 and 3 pins, 5 mm

If necessary, you can change the ignition and decay time of the LEDs by selecting the value of resistance R2, as well as selecting the capacitance of the capacitor.

JOB:
?????????????????????????????????????????
?1? In this post I will show in detail how to make a board with a control plus. The board with a control minus is made in a similar way, even a little simpler due to the smaller number of elements. We mark the boundaries of the future board on the PCB. We make the edges a little larger than the pattern of the paths, and then cut them out. There are many ways to cut PCB: with a hacksaw, metal scissors, using an engraver, and so on.

Using a utility knife, I made grooves along the marked lines, then sawed them out with a hacksaw and sharpened the edges with a file. I also tried using metal scissors - it turned out to be much easier, more convenient and dust-free.

Next, sand the workpiece under water with P800-1000 grit sandpaper. Then we dry and degrease the surface of the board with 646 solvent using a lint-free cloth. After this, you must not touch the surface of the board with your hands.

2? Next, using the SprintLayot program, open and print the diagram on a laser printer. You only need to print the layer with tracks without markings. To do this, when printing in the program, at the top left in the “layers” section, uncheck unnecessary boxes. Also, when printing, in the printer settings we set high definition and maximum image quality. I uploaded the program and slightly modified diagrams for you to Yandex.Disk.

Using masking tape, glue a glossy magazine page/glossy photo paper (if their size is smaller than A4) onto a regular A4 sheet and print our diagram on it.

I tried using tracing paper, glossy magazine pages and photo paper. It is most convenient, of course, to work with photographic paper, but in the absence of the latter, even magazine pages will do just fine. I don’t recommend using tracing paper - the design on the board is printed very poorly and will turn out unclear.

3? Now we warm up the textolite and attach our printout. Then use an iron with good pressure to iron the board for several minutes.

Now let the board cool completely, then put it in a container of cold water for a few minutes and carefully remove the paper from the board. If it doesn’t come off completely, then roll it up slowly with your fingers.

Then we check the quality of the printed tracks, and touch up the bad places with a thin permanent marker.

4? Using double-sided tape, glue the board onto a piece of foam plastic and place it in a ferric chloride solution for several minutes. The etching time depends on many parameters, so we periodically remove and check our board. We use anhydrous ferric chloride, dilute it in warm water according to the proportions indicated on the package. To speed up the etching process, you can periodically shake the container with the solution.

After the unnecessary copper has been removed, we wash the board in water. Then, using a solvent or sandpaper, remove the toner from the tracks.

5? Then you need to drill holes for mounting the board elements. To do this, I used a drill (engraver) and drills with a diameter of 0.6 mm and 0.8 mm (due to the different thickness of the legs of the elements).

6? Next you need to tin the board. There are many different ways, I decided to use one of the simplest and most accessible. Using a brush, we lubricate the board with flux (for example LTI-120) and tin the tracks with a soldering iron. The main thing is not to keep the soldering iron tip in one place, otherwise the tracks may come off due to overheating. We take more solder onto the tip and move it along the path.

7? Now we solder the necessary elements according to the diagram. For convenience, in SprintLayot I printed out a diagram with symbols on plain paper and, when soldering, checked the correct arrangement of the elements.

8? After soldering, it is very important to completely wash off the flux, otherwise there may be shorts between the conductors (depending on the flux used). First, I recommend thoroughly wiping the board with 646 solvent, and then rinsing it well with a brush and soap and drying it.

After drying, we connect the “constant plus” and “minus” of the board to the power supply (“control plus” is not touched), then instead of the LED strip we connect a multimeter and check if there is voltage. If at least some voltage is still present, it means there is a short somewhere, perhaps the flux was not washed off well.

PHOTOS:

When designing amplifier power supplies Often problems arise that have nothing to do with the amplifier itself, or that are a consequence of the used element base. So in power supplies transistor amplifiers With high power, the problem often arises of implementing a smooth switching on of the power supply, that is, ensuring a slow charge of electrolytic capacitors in the smoothing filter, which can have a very significant capacity and, without taking appropriate measures, will simply damage the rectifier diodes at the moment of switching on.

In power supplies for tube amplifiers of any power, it is necessary to provide a feed delay high anode voltage before warming up the lamps, in order to avoid premature depletion of the cathode and, as a result, a significant reduction in the lamp life. Of course, when using a kenotron rectifier, this problem is solved by itself. But if you use a conventional bridge rectifier with an LC filter, you cannot do without an additional device.

Both of the above problems can be solved by a simple device that can be easily built into both a transistor and a tube amplifier.

Device diagram.

The schematic diagram of the soft start device is shown in the figure:

Click to enlarge

The alternating voltage on the secondary winding of transformer TP1 is rectified by the diode bridge Br1 and stabilized by the integrated stabilizer VR1. Resistor R1 ensures smooth charging of capacitor C3. When the voltage across it reaches a threshold value, transistor T1 will open, causing relay Rel1 to operate. Resistor R2 ensures the discharge of capacitor C3 when the device is turned off.

Inclusion options.

The Rel1 relay contact group is connected depending on the type of amplifier and the organization of the power supply.

For example, to ensure smooth charging of capacitors in the power supply transistor power amplifier, the presented device can be used to bypass the ballast resistor after charging the capacitors in order to eliminate power losses on it. A possible connection option is shown in the diagram:

The values ​​of the fuse and ballast resistor are not indicated, since they are selected based on the power of the amplifier and the capacitance of the smoothing filter capacitors.

In a tube amplifier, the presented device will help organize a feed delay high anode voltage before the lamps warm up, which can significantly extend their service life. A possible inclusion option is shown in the figure:

The delay circuit here is turned on simultaneously with the filament transformer. After the lamps have warmed up, relay Rel1 will turn on, as a result of which the mains voltage will be supplied to the anode transformer.

If your amplifier uses one transformer to power both the lamp filament circuits and the anode voltage, then the relay contact group should be moved to the secondary winding circuit anode voltage.

Elements of the switch-on delay circuit (soft start):

• Fuse: 220V 100mA,
• Transformer: any low-power with an output voltage of 12-14V,
• Diode bridge: any small-sized one with parameters 35V/1A and higher,
• Capacitors: C1 - 1000uF 35V, C2 - 100nF 63V, C3 - 100uF 25V,
• Resistors: R1 - 220 kOhm, R2 - 120 kOhm,
• Transistor: IRF510,
• Integral stabilizer: 7809, LM7809, L7809, MC7809 (7812),
• Relay: with an operating winding voltage of 9V (12V for 7812) and a contact group of the appropriate power.

Due to the low current consumption, the stabilizer chip and field-effect transistor can be mounted without radiators.

However, someone may have the idea to abandon the extra, albeit small-sized, transformer and power the delay circuit from the filament voltage. Considering that the standard value of the filament voltage is ~6.3V, you will have to replace the L7809 stabilizer with an L7805 and use a relay with a winding operating voltage of 5V. Such relays usually consume significant current, in which case the microcircuit and transistor will have to be equipped with small radiators.

When using a relay with a 12V winding (somehow more common), the integrated stabilizer chip should be replaced with a 7812 (L7812, LM7812, MC7812).

With the values ​​of resistor R1 and capacitor C3 indicated in the diagram delay time inclusions are of the order 20 seconds. To increase the time interval, it is necessary to increase the capacitance of capacitor C3.

The article was prepared based on materials from the magazine "Audio Express"

Free translation by the Editor-in-Chief of RadioGazeta.