Smooth switching on of incandescent lamps: your light bulbs will stop burning out. To prevent light bulbs from burning out: a soft-start circuit. Do-it-yourself radio engineering, electronics and circuits Do-it-yourself soft start of halogen lamps

Incandescent lamps last about 1000 hours, but if they are turned on and off frequently, their service life becomes even shorter. You can extend the service life by installing a soft-start device for incandescent lamps, and the described method is also suitable for protecting halogen lamps.

Causes of premature burnout

Incandescent lamps are an old light source, their design is extremely simple - a tungsten spiral is installed in a sealed glass bulb, when current flows through it, it heats up and begins to glow.

However, such simplicity does not mean durability and reliability. Their service life is about 1000 hours, and often even less. The cause of burnout can be:

voltage surges in the supply network;
frequent switching on and off;
other reasons such as temperature changes, mechanical damage and vibrations.

In this article we will look at how to minimize the harm from frequent lamp switching on. When the light bulb is turned off, its coil is cold. Its resistance is 10 times lower than that of a hot coil. The main operating mode is the hot state of the lamp. From Ohm's law it is known that the current depends on the resistance; the lower it is, the higher the current.

When you turn on the lamp, a lot of current flows through the cold filament, but as it warms up, it begins to decrease. The initial high current has a destructive effect on the coil. In order to avoid this, you need to organize a smooth switching on of incandescent lamps.

Dimmer for smooth switching

Principle of operation

To limit the turn-on current of an incandescent lamp, you can lower the initial voltage and gradually increase it to the nominal value. To do this, use a device for smoothly switching on incandescent lamps.

The device is connected to the break in the supply wire between the switch and the lamp. When you apply voltage, at the first moment it is close to zero, the soft ignition circuit gradually increases it. They are usually assembled according to a phase-pulse regulator circuit using thyristors, triacs or field-effect transistors.

The rate of voltage rise depends on the circuit design of the device, usually 2–3 seconds from 0 to 220 V.

The main characteristic of the protection unit is the permissible power of the connected load. Usually lies in the range of 100–1500 W.

Ready solutions

Protection blocks for lamps are sold in almost every household and electrical goods store. Such a unit may be called differently than stated above, for example: “Protection device for halogen and incandescent lamps” or another similar name. As already noted, when purchasing, the main thing you should pay attention to is the power of the ignition unit.

A wide range of such devices are produced under the Granit brand.

Offer from "Granit"

There are also miniature Navigator units; they can be conveniently hidden in the junction box if it is not filled to the brim with wires. Will also fit inside most light fixtures, such as the base of a table lamp, or between the ceiling and chandelier if possible.

Compact protection unit

Scheme

Since the device for smoothly switching on incandescent and halogen lamps is not particularly difficult from a circuit design point of view, you can assemble it yourself. The assembly process can be carried out:

hanging installation;
on a breadboard;
on the printed circuit board.

And depending on your skills and capabilities, the most reliable option will be the one on a printed circuit board; in this case, it is better to stay away from wall-mounted installation if you do not know the specifics of such installation in 220 V circuits.

Smooth switching on of 220 V lamps: thyristor circuit

The first diagram is shown in the figure below. Its main functional element is a thyristor connected in the arms of the diode bridge. The denominations of all elements are signed. If you use it as a smooth ignition for a floor lamp, table lamp or other portable lamp, it is convenient to enclose it in a housing; a distribution box for external installation is suitable. At the exit, install a socket for connecting a lamp. In fact, this is a regular dimmer, and there is no soft start as such. You simply turn the potentiometer knob, gradually increasing the voltage across the lamp. By the way, such an attachment is also suitable for adjusting the power of a soldering iron or other electrical appliances (stove, commutator motor, etc.).

Scheme implementation option

Smooth switching on of 220 V lamps: triac circuit

You can reduce the number of parts and assemble the same circuit that is installed in proprietary protection units. It is shown in the figure below.

Circuit with triac

The longer the time constant R2С1 of the chain, the longer the ignition takes. To increase the time, you need to increase the capacitance C1, please note - this is a polar or electrolytic capacitor. Capacitor C2 must withstand a voltage of at least 400 V - it is a non-polar capacitor.

To increase the power of the connected lamps, change the triac VS1 to any current suitable for your load.

Choke L1 is a filter element; it is needed to reduce interference in the network from turning on the triac. It is not necessary to use it; it does not affect the operation of the circuit.

When SA1 (switch) turns on, current begins to flow through the lamp, inductor and capacitor C2. Due to the reactance of the capacitor, the current flows through the lamp is small. When the voltage to which C1 is charged reaches the opening threshold of the triac, current will flow through it, the lamp will turn on at full heat.

Smooth switching on of 220 V lamps: circuit based on IC KR1182PM1

There is also an option for smooth start-up using the KR1182PM1 microcircuit; it provides smooth start-up of lamps and other loads with a power of up to 150 W. You will find a detailed description of this chip here:

and below is a diagram of the device, it is extremely simple:

Simple scheme

Or here is its modernized version to enable a powerful load:

Well-developed scheme

Additionally, a BTA 16–600 thyristor is installed, it is designed for a current of up to 16 A and a voltage of up to 600 V, this can be seen from the markings, but you can take any other one. Thus, you can turn on a load of up to 3.5 kW.

Smooth switching on of 12 V lamps

Lamps with a voltage of 12 V are often used for spotlights. Electronic transformers are currently used to convert 220 to 12 V. Then the soft start device must be connected to the break in the supply wire of the electronic transformer.

Smooth switching on of lamps in a car

If the task is to organize the smooth switching on of 12 V car lamps, then such circuits will not work here. The car's electrical circuit uses 24 or 12 V DC voltage. Here you can use linear or pulse circuits, so-called PWM regulators.

The simplest option would be to use a two-stage switching circuit.

Two-stage switching circuit

This circuit is installed in parallel with the lamps being switched on. At first, current flows through the resistor and the lamps glow dimly. After a short time, about half a second, the relay turns on and current flows through its power contacts, they in turn bypass the resistor and the lamps light up at full brightness.

The resistor value is from 0.1 to 0.5 Ohm, it must be of high power - about 5 W, for example, in a ceramic case.

The second option is to assemble a pulse unit for smooth ignition. His scheme is more complicated:

A more difficult option to implement

List of components:

Resistors:

R1=2 k.
R2=36 k.
R3=0.22.
R4=180.
R5, 7=2.7 k.
R6=1 M.

Capacitors:

C1=100 n.
C2=22×25 B.
C3=1500 p.
C4=22×50 B.
C5=2 µF.

Microcircuit MC34063A or MC34063A, or KR1156EU5.
Field effect transistor IRF1405 (or any N-channel with similar parameters: IRF3205, IRF3808, IRFP4004, IRFP3206, IRFP3077).
Choke 100 µH, current not less than 500 mA.
LEDs.
Diodes 1N5819.

The on time is regulated by circuit R6C5. Increase the capacity to increase the time.

If it is difficult for you to make such a circuit, you can buy a ready-made assembly, such as the EKSE-2A-1 autocontroller (25 A/IP54) or any other suitable one. This particular model has 2 channels for each headlight, 8 operating programs. It is based on a PIC microcontroller.

Incandescent lamp and its features

Many people have probably noticed that an incandescent lamp burns out mainly when turned on. This happens because at the moment of switching on the cold filament of the lamp has a low resistance, a current surge occurs that exceeds the operating current of the lamp. It is this current surge that has a detrimental effect on the lamp, reducing its service life. In order to extend and increase the service life of the lamp, you need a device that, at the moment of switching on, will smoothly increase the current from the minimum to the nominal value. There are many schemes and ready-made devices; I offer my own version of a device for increasing the service life of incandescent lamps, which you can easily assemble yourself.

Scheme

Technical characteristics at the ratings indicated in the diagram

Load power: 500W*
Input operating voltage: ~ 230V
Output voltage: about ~200V
Smooth voltage rise time from 0 to 200V: about 3 seconds
Recovery time after shutdown: about 30 seconds*

Notes

The power of the incandescent lamp used will depend on the cooling of the triac; with a load of up to 150 W, you can do without a radiator.

Compared to microcontroller devices, this type of device has the main disadvantage of the need for recovery. The fact is that it is the charging time of the discharged capacitance of capacitor C1 that sets the time for the smooth increase in voltage at the output of the device, and after turning off the device, the discharge time of the capacitor C1 through R1 is approximately 25-30 seconds. In fact, it turns out that if you turn the device on/off at intervals of less than 10 seconds, the rate of voltage rise across the lamp will be high, and there will be no smooth switching effect.

Also, at the moment of switching on, a nonlinearity in the rate of voltage rise is observed (this is not critical and is not a disadvantage). For example, in 1 second the voltage rises from 0 to 70V, in 0.5 seconds from 70 to 120V, in 1.5 seconds from 120 to 200V.

Setup and installation

By reducing resistance R1, the recovery time of the device is reduced, but at the same time the operating voltage on the incandescent lamp is reduced. As the resistance R2 decreases, the time of smooth voltage rise across the lamp decreases, while the operating voltage increases. Also, by increasing the capacitance C1, you can increase the time of smooth voltage rise, but the recovery time of the device will increase. I advise you to configure the device with resistor R2; it needs to be selected so that the voltage across capacitor C1 is approximately 4.5V.

Please note that I soldered C3 by surface mounting, since I did not immediately realize that it was needed in this device, if desired, it can be easily added to the board.

Good luck to all! Be careful with high voltage!

List of radioelements

Designation	Type	Denomination	Quantity	Note	My notepad
VS1	Triac	BT136-600E	1		To notepad
VD1, VD2	Rectifier diode	1N4148	2		To notepad
C1		1000uF 6.3V	1		To notepad
C2	Electrolytic capacitor	47uF 50V	1		To notepad
C3	Capacitor	10-22nF 630V	1	Metal film	To notepad
R1	Resistor	22 kOhm	1		To notepad
R2	Resistor

The warranty life of an ordinary incandescent lamp declared by manufacturers is 1000 hours. This is about 40 days of continuous work. But in practice, the “Ilyich light bulb” lasts much longer. And thanks to this, its popularity among consumers does not decrease. The only weak point of the lamp is the tungsten filament, which is sensitive to sudden changes in voltage in the network. But there are simple devices that eliminate this risk and smooth out uneven current supply.

Operating principle of UPVL

The soft-start device is applicable for incandescent lamps with tungsten filament. In addition to a number of household lamps, this category also includes halogen lamps, which are used in powerful floodlights. The principle of operation of the device is to slow down the supply of voltage to the filament at the moment of switching on. This makes it possible to smoothly heat up the coil, bypassing the jump phase, which lasts hundredths of a second. As you know, it is at this moment that burnout most often occurs. Thanks to the action of the electronic circuit of the device, the current is supplied with a gradual increase, for 1 to 3 seconds.

The tungsten filament of an incandescent lamp at room temperature has low resistance, which leads to high currents and burnout of the filament when turned on

The longest burning lamp in the world, listed in the Guinness Book of Records, was recorded in the city of Livermore, California. From 1901 to the present day, this “hundred-year lamp,” as it was dubbed, has continuously illuminated the fire station. Moreover, over all these years it was turned off only a few times for a short time. Modern researchers often cite it as confirmation of the theory of “planned obsolescence.”

The "Century Lamp" was handcrafted and features a carbon spiral

The soft start device has small dimensions and weight. And thanks to this you can install it:

in the protective cap of the chandelier where the wires exit;
in the switch socket;
in a junction box;
in the space above a suspended or suspended ceiling.

The dimensions of the device allow installation even in the cavity of a socket box

The installation location is selected based on accessibility and ease of installation. The best option is considered to be one in which the device has good natural ventilation. The connection diagram is simple - the device crashes into a break in one of the conductors (phase or neutral) of the supply cable.

The soft-start device crashes into a break in one of the wires that are connected to the lamp

If incandescent lamps with an operating voltage of 12 V are used for lighting, the UPVL is installed in front of the step-down transformer. With this connection, protection from unfavorable network surges also extends to the transformer, which is also important.

One of the positive side effects of soft-ignition lighting is the softening of the harsh glare at the moment of switching on. This protects human eyes from unnecessary overload, especially when the light is turned on in complete darkness.

The UPVL device is not used for fluorescent and LED lamps, since they operate on different design principles.

To calculate the power of the UPVL, the total power of consumers is calculated. In practice, this is expressed by adding up the power ratings of all the lamps to which the device will be connected. To ensure that the device does not operate at the limit of its capabilities, 20% is added to the total power. For example, if the circuit is supposed to include 5 lamps of 100 W each, then their total consumer power will be 500 W. To this number add 20% - 100 W and get the desired value of the UPVL power - 600 W.

The soft start device can be installed inside the junction box

A chain of stores selling electrical goods sells factory-produced UPVLs. Among them there are both domestic and foreign models. The names may vary, but in principle it is a plastic container with dimensions smaller than a matchbox. Often the emphasis in the name is on the protective function of the device for halogen lamps. But the device is quite applicable to ordinary incandescent lamps. Another possible name for the device is a phase regulator. This is usually the name given to more powerful UPVLs with a slightly modified control system. The price of such a device can vary from 300 to 600 rubles, depending on the rated power.

The lamp soft start device must not be used to smoothly start the motors of power tools and other household appliances.

For those who have basic knowledge of radio electronics, we can offer independent production of UPVL. Here are several schemes with which you can extend the life of a lighting lamp many times over.

Thyristor circuit

The thyristor circuit uses simple and accessible parts. The basis is the thyristor VS1 and four diodes VD1 - VD4, connected into a rectifier bridge. In addition, you will need a capacitor C1 with a capacity of 10 μF and resistors R1 (variable capacity) and R2.

In a thyristor circuit, voltage is supplied to the lamp after a period of time, which is set by variable resistance R1

When voltage is applied, electric current passes through the lamp coil and is rectified in the diode bridge. After passing through the resistor, charging of the capacitor begins. Reaching the voltage threshold, the thyristor opens and lamp current flows through it. As a result, the tungsten filament gradually heats up. Using a variable-capacity resistor R1, you can adjust the “acceleration” time of the lamp.

Triac circuit

Using triac VS1 as a power switch results in fewer parts being used in the circuit.

The operating principle of a triac circuit is similar to a thyristor circuit, but it contains fewer parts

Throttle element L1 serves to suppress interference when the power switch is opened. By and large, it can be excluded from the scheme if necessary. The circuit that sets the time consists of resistance R2 and capacitor C1, fed through diode VD1. Resistance R1 reduces the current at control electrode VS1. The principle of operation of the circuit is similar to the previous one - a temporary pause is created while the capacitor is filled, the triac opens and current flows through it, powering the EL1 lamp.

The device, based on a triac regulator circuit with a variable capacitor, has compact dimensions due to the small number of parts

Circuit on a specialized chip

The circuit is based on a specialized microcircuit KR1182PM1 (or DIP8 in the imported version), equipped with two thyristors and two systems for their control. Capacitance C3 and resistance R2 regulate the duration of the on (off) time. To separate the control and power parts, a triac VS1 is used, the current on the control electrode sets the resistance R1. External capacitors C1 and C2 are installed to regulate the operation of the thyristors of the internal circuit of the microcircuit. To protect against interference, resistor R4 and capacitor C4 are used.

UPVL based on a specialized microcircuit not only smoothly turns on and off the lamp with a slight delay, further increasing its service life

When connecting the device to the voltage supply line to the lamp, the contacts of switch SA1 must be in the closed position. Capacitor C3 gains capacity when contacts SA1 open. During a gradual increase in current through resistance R1, which controls the power switch at the output of the IC, the triac VS1 and the lamp EL1 connected to it in series start up smoothly.

It is noteworthy that this circuit not only slows down the heating of the coil during switching on, but also slows down its extinction. The lamp goes out as smoothly as it comes on. The delay duration is set at the device assembly stage by selecting the capacitance of capacitor C3. If desired, you can increase the lamp start delay to 10 seconds. The smoothness of shutdown is controlled by resistance R2.

Do not confuse the device for smoothly switching on a lamp with a dimmer. UPVL is an automatic regulator that smoothly increases the current on the lighting device at the moment of switching on. A dimmer is a device that is used to manually adjust the brightness of lighting.

A characteristic property of UPVL and phase regulators is that the device reduces the output voltage to the lamp (from 230 to 200 V). This further increases its service life.

Video: device for smoothly switching on a lamp using field-effect transistors

Application of a soft start device

Installation of the device does not require high qualifications. Anyone with a screwdriver and a voltage indicator can handle the installation. In the cable leading to the lamp, a break is made in one phase or neutral wire and the device is connected to it. It is best to fasten the wires using terminal blocks, as this guarantees a stable and reliable connection. If it is not possible to use terminal blocks, it is recommended to solder the twists with tin solder.

Operation of the UPVL does not require additional attention. Factory models come with a warranty of up to 3 years. In practice they work much longer.

When assembling the device, one should not forget that high mains voltage can cause harm to human health. Before connecting the wires, you must make sure that there is no current in the lamp power cable.

Video: how a phase regulator works on triacs

A device for smoothly switching on a lamp saves not only energy consumption, but also the cost of purchasing burnt-out lamps.

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.

Thyristor circuit

In the circuit of the rectifier bridge VD1, VD2, VD3, VD4, EL1 is used as a load and current limiter. The rectifier arms contain thyristor VS1 and a shift chain R1 and R2, C1. The installation of a diode bridge is determined by the specific operation of the thyristor.

After applying voltage to the circuit, current flows through the filament and enters the rectifier bridge, then the electrolyte capacity is charged through the resistor. When the voltage reaches the opening threshold of the thyristor, it opens and passes the incandescent light bulb current through itself. This results in a gradual, smooth heating of the tungsten coil. The warm-up time depends on the capacitance of the capacitor and resistor.

Triac circuit

The triac circuit contains fewer parts due to the use of triac VS1 as a power switch. Element L1 for suppressing interference that occurs when opening the power switch can be excluded from the circuit. Resistor R1 limits the current to the control electrode VS1. The time-setting circuit is made of resistor R2 and capacitance C1, which are powered through diode VD1. The operating scheme is similar to the previous one; when the capacitor is charged to the opening voltage of the triac, it opens and current begins to flow through it and the lamp.

The photo below shows a triac regulator. In addition to regulating the power in the load, it also smoothly supplies current to the incandescent lamp during switching on.

Circuit on a specialized chip

The Kr1182pm1 microcircuit is specially designed for building all kinds of phase regulators.

In this case, the microcircuit itself regulates the voltage on an incandescent light bulb with a power of up to 150 watts. If you need to control a more powerful load, a larger number of illuminators at the same time, a power triac is added to the control circuit. How to do this, see the following figure:

The use of these soft-start devices is not limited only to incandescent lamps; they are also recommended to be installed together with halogen lamps for 220 V. Devices similar in operating principle are installed in power tools that smoothly start the motor armature, also extending the service life of the device several times.

Important! It is strictly not recommended to install this device with fluorescent and LED sources. This is due to different circuit designs, operating principles, and the presence of each device’s own source of smooth heating for compact fluorescent lamps or the absence of the need for this regulation for LEDs.