Dimmer circuit on a triac for a table lamp. Dimmer for incandescent lamps. Dimmer for LED strip

Readers often ask questions about repairing dimmers with their own hands.

Therefore, I decided to supplement this information and highlight it in a separate article. which you are reading now.

As always, there will be many photos with explanations, because it's better to see once!

An example will be shown of how I repaired the dimmer with my own hands. There will be self-criticism and useful advice.

Causes of dimmer failure

Most often, the cause of a breakdown can be an excess of the maximum allowable load or a short circuit in the load. Exceeding the load happens when, for example, lovers of good lighting screw too powerful lamps into chandeliers. Or several lamps are connected through a dimmer, consuming too much power in total.

By the way, when choosing a dimmer, you should choose the power with a margin of 30 ... 50%. How to increase the power of the dimmer will be described and shown in this article.

A short circuit is possible not only due to faulty wiring. It happens that when the light bulbs burn out, a short circuit (short circuit) occurs in them, we will not delve into the nature of which.

Malfunctions of dimmers on the triac

As a result of short circuit and overload, as a rule, triac fails. This is the main malfunction, it occurs in 90% of breakdown cases.

The triac is the main element. Its distinguishing features are three outputs and a radiator is screwed to the case. The most common models are BT137, BT138, BT139.

A triac malfunction can be detected with a multimeter. If you ring in the ohmmeter mode, the resistance between terminals A1 and A2 (or T1 and T2, the first and second outputs) will be from zero to several ohms. Conclusion - the triac definitely burned out.

There is another case - the triac rings normally (infinite resistance), but the dimmer does not work, however (the lamp does not light in all positions of the regulator). Only verification will help here, i.e. inclusion in the real scheme.

The replacement of the triac will be discussed in detail below.

Cream of a faulty triac, there are other dimmer faults:

1. The power tracks of the printed circuit board burn out. This is a consequence of the main malfunction. The tracks will have to be restored with jumpers.
2. The mechanical integrity of the regulator (potentiometer, or variable resistor) is violated. From frequent and intensive use, there is no need for explanation.
3. In dimmers that have a fuse, you must first check it before repairing. Often the manufacturer attaches a spare, which is stored in the same place, in the dimmer, where the worker is. Rational decision. If he were in a separate bag, he would definitely be lost.
4. Mechanical breaking of contacts and soldering of the printed circuit board. First of all - soldering the contacts where the wires are screwed. It also happens that electronic elements are simply badly soldered by the manufacturer.
5. Malfunctions of individual elements. First of all - dinistor, then resistors and capacitors.

Dimmer circuit

Before repairing, let's look at the dimmer circuit. Compared to the pro dimmer, I reworked the circuit a little and clarified it. In the last article, the scheme was left the same. And in the new part numbering did not change, so as not to introduce confusion.

The dimmer, which we will repair, has just such a scheme.

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Dimmer repair procedure

Now I will give an example of how to replace a triac with your own hands, using a drill, a soldering iron, and an ordinary toothpick.

The triac can be replaced by unscrewing the heatsink and removing the triac from the board. But the radiator is now riveted. The rivet is much more technologically advanced and cheaper in mass production.

Therefore, we pick up a drill with a drill with a diameter of 3.5 ... 5.5 mm.

The arrow shows the direction of the drill.

2 Remove the radiator from the triac

The radiator is removed, now you need to carefully unsolder the bad triac, minimally damaging the board. The recommended soldering iron power is 25 or 40 watts.

3 We solder the triac from the board. The conclusions of the triac are marked - T1, T2, Gate.

Plus, a soldering iron requires experience and skill.

A soldering iron with a power of 60 watts or more can easily damage the board.

The pads stuck together, but it's not important yet.

And here are the triac friends, next to the DB3 dinistor:

Triacs (BT139, BT138, BT137) in the photo are all for a voltage of 800 Volts, the maximum operating current is 16, 12, and 8 Amps, respectively.

The datasheet can be downloaded at the end of the article.

Now we insert a new part into these through holes:

9 Cut off the legs (conclusions))

The jumper is unsuccessful, it was necessary to use thinner wires ...

We carefully check the soldering so that there is no short circuit between the pads.

Now it remains to check the operation in a real switching circuit. I remind you that the dimmer turns on in the same way as a regular switch:

For the test circuit, I use a light bulb of any power in the cartridge, a wire with a plug, and a terminal block.

Two more dimmers. Appearance of printed circuit boards.

Bonus - more photos:

Resistors are color-coded. Learned how?

Dimmer circuit. Non-standard?

Download reference information on triacs for dimmers:

/ Datasheet, pdf, 183.12 kB, downloaded: 8909 times./

/ Datasheets, pdf, 150.55 kB, downloaded: 11792 times./

If you buy a triac, then on Aliexpress in China these cost a penny, in this case, 10 rubles / piece.

You also need to take into account the advantage of BTA triacs over BT - the BTA flange (radiator) is isolated from live parts, and this increases safety!

Similarities between dimmers and lamp protection units

Lamp protection blocks that smoothly turn on the brightness of the lamps, I described in detail in my articles about such blocks.

The difference between dimmers and BZ is only in the way of control. In protection units, the triac is controlled by the controller according to the program. And the program can be anything, up to a wave-like change in brightness. Can be controlled by any analog or digital signal. There would be demand.

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A dimmer is a newfangled name for a device, more often referred to as a dimmer switch, and is designed to smoothly control the power of electrical appliances, primarily lamps (in English, "dim" means "dim"). The thing in the household is very useful, but it is not necessary to buy it at all. In the sense that anyone who has ever held a soldering iron in their hands can make such a device with their own hands. Next, we will describe how this is done.

The simplest kind of dimmers can be considered any variable resistor, for example, a rheostat known to everyone from school. If you turn it on in series with an incandescent lamp, then when you change the position of the slider, its brightness will change. However, it is extremely unprofitable to use such a dimmer, since it does not reduce the power consumption, but only “pulls” part of it onto itself, turning it into heat.

General view of the dimmer

A practical version of the dimmer is an autotransformer. The secondary winding of this device has several pairs of terminals, on which a different output voltage is formed. When a load is connected to one or another pair, it will work with different power.

Dimmers based on autotransformers have a number of advantages:

• consume from the supply network only the power that is currently needed;
• regardless of the ratio of input and output voltages, they give a sinusoidal current at the output with virtually no distortion;
• do not interfere.

But such devices are relatively large and heavy, and mechanical switches have to be used for adjustment, so that they are used today only in rare cases.

By now, electronic dimmers assembled on semiconductor elements have become popular. These are compact, weightless devices.

The principle of operation of an electronic dimmer

Power regulation does not consist in converting voltage, as is the case with a transformer: a dimmer passes current only at a certain value of it (voltage). Recall that the voltage in the AC network constantly fluctuates along a sinusoid from -230 V to + 230V.

Factory made electronic dimmer

That is, an electronic dimmer is a high-frequency switch that has time to turn on and off during each half-cycle of alternating current. Thus, the load is connected to the network not all the time, but only for a certain fraction of a half-cycle, due to which the average voltage and electric current power decrease.

It is obvious that the current at the output of an electronic dimmer is no longer a sinusoidal characteristic: it is rather some kind of its variable-pulsating variety. If you build a graph, a part of each sinusoid wave will be cut off, as it were.

It is important to know that such power is not suitable for all devices. In those that require low harmonic current, the winding may overheat, causing the device to fail.

From household consumers, this category primarily includes:

• electric motors;
• devices with a switching power supply;
• transformer-powered devices: televisions, radios, fluorescent lamps with electronic ballast;
• induction transformers for halogen lamps.

But all of the above applies only to the simplest electronic dimmers with a classic circuit. More complex dimmers, which by now have not only been developed, but are also mass-produced, are "omnivorous" - they can be connected to any load. The main thing is to choose the right model.

Electronic dimmers have one more drawback: in the simplest version (such models are the cheapest), they are a source of tangible electromagnetic interference both in the radio frequency range and in the wires connected to them. In the room where the dimmer is installed, it may be difficult to listen to the radio, there may be malfunctions in the operation of measuring equipment, as well as sound recording - in the form of a background.

There is a way to eliminate it - you need to improve the circuit by supplementing it with a filter. In this capacity, chokes are used, they can be supplemented with capacitors (inductive-capacitive filter). Dimmers with filters are somewhat more expensive.

An incandescent lamp, which is supplied with a voltage reduced by an electronic dimmer, makes a whistling sound, barely audible, but clearly noticeable in complete silence. The more powerful the lamp, the more intense the whistle will be. The fact is that the peculiar current received at the output of the dimmer causes mechanical vibrations in the filament, which lead to the appearance of such a sound.

This phenomenon is called magnetostriction. It also takes place when connected directly, that is, without a dimmer, but in this case it manifests itself to a much lesser extent, and does not produce sounds audible to a person.

How to make a device with your own hands

A conventional dimmer is simple and cheap to manufacture, since it requires a small number of quite affordable radio components. Here are the main ones:

A few words should be said about the assembly of the dimmer. The simplest is the so-called hanging installation, when all the elements are connected into a single circuit by means of wires.

It looks like a dimmer assembled by a hinged method

Before soldering, the stripped strands of a piece of wire cut to the desired length, as well as the “legs” of radio components, must be tinned with a soldering iron (solder and a special flux or rosin are used).

Materials for connecting wires by soldering

After soldering, all connections should be wrapped with electrical tape. If this is not done, a short circuit may occur due to careless contact or moisture.

A more complicated option is to assemble a dimmer on a homemade printed circuit board.

Assembly of a dimmer on a printed circuit board

Its manufacture requires some skill, but the device will turn out to be miniature and more reliable. Tracks on the board, as well as wire cores for surface mounting, must be tinned. The soldering process is also no different.

Now consider several circuits of electronic dimmers.

On triac

This device is designed to be connected to a network with a voltage of 220 V. As you can see, in addition to the triac and dinistor, there is an RC circuit here. It has a voltage divider, consisting of a variable resistor R1 and a constant R2.

Triac dimmer circuit

The circuit works like this:

1. The user sets the resistance R1, which determines the voltage in the circuit R2 - C1. From this voltage, in turn, depends on the charging time of the capacitor C1.
2. When the voltage on it reaches a certain value, it causes the DB3 dinistor, which is included in the same circuit between R2 and C1, to open.
3. At the same time, a pulse is applied through DB3 to the triac VS1, which opens and passes current to the load. The faster C1 is charged, the earlier VS1 will open and, accordingly, the longer will be that part of the half-cycle during which the current is passed to the load. Consequently, the electrical power will be greater.

The process of adjusting the intensity of lighting with such a dimmer is displayed on the graph:

Light intensity control chart

The time for which the charge in C1 reaches the opening threshold DB3 is denoted by t*.

On thyristors

Thyristors are good because they can be removed from old electrical appliances, such as televisions. Thus, the dimmer will turn out to be practically free. Here is his diagram:

Thyristor dimmer circuit

Thyristors, unlike triacs, pass current in only one direction, so for a given dimmer they will need two - one for each half-wave of alternating current. Accordingly, you will also need two dinistors, through which, as in the first circuit, a control pulse is formed.

According to the principle of operation, the scheme is very similar to the previous one:

1. A positive half-wave through the circuit R5 - R4 - R3 charges the capacitor C1.
2. As soon as the voltage on C1 is sufficient to open the dinistor V3, it (the dinistor) will pass a control pulse to the thyristor electrode V
3. V1 will open and allow current to flow to the load.
4. With a negative half-wave, the thyristor V2 will work in the same way, while V1 will be closed. The charge of the capacitor in this case is carried out through the circuit R1 - R2 - R

Condenser dimmer

Unlike the first two, this version of the dimmer allows you to reduce the power only by a certain fixed amount, that is, an intermediate brightness level of the lamp appears. However, it is very compact.

Condenser dimmer

The principle of operation is extremely simple. As you know, an alternating current can flow through the circuit in which the capacitor is connected, but its power will depend on the capacitance of the capacitor. The faster it charges (small capacity), the smaller the fraction of the half-wave will have time to pass through the circuit. And vice versa - with a large capacity, even the entire half-wave can do useful work.

Therefore, you need to choose a capacitor with the right capacity and connect it to the circuit so that you can direct the current either through it (reduced power) or bypassing it (100% power).

You can include another capacitor in the circuit with the ability to switch between it and the first capacitor (you will need a 4-position switch). Then an additional step of power adjustment will appear.

Capacitors can be used paper, non-polar, available in abundance in old electrical appliances. Their capacity is selected according to the following table:

Capacitance-Voltage Parameter Table

On a chip

Now let's consider a dimmer for direct current with a voltage of 12 V. It is most convenient to assemble such a regulator on a KREN microcircuit - an integrated stabilizer.

Dimmer circuit on a chip

Due to the use of a microcircuit, the design of the device is extremely simplified, respectively, the amount of assembly work becomes minimal. In addition, such dimmers have a protection function.

To adjust the power, as in the first two circuits, a variable resistor is used (in the diagram - R2). The value of the reference voltage on the control electrode KREN depends on its resistance, on which, in turn, the output voltage depends. The adjustment range is very wide - from 12 V (100%) to a few tenths.

It should be noted that the KREN chip heats up quite a lot, which is why it has to be equipped with a relatively large heatsink. To a much lesser extent, this drawback manifests itself in dimmers assembled on the basis of the 555 integrated timer and the KT819G transistor controlled by it (it plays the role of an electronic switch like a thyristor and triac).

The control signal is short PWM pulses that switch the transistor to either a fully open or fully closed position, so that the voltage drop across it is the smallest possible. Accordingly, the scheme turns out to be more economical than on the basis of KREN, and due to the use of a smaller radiator, it is also more compact.

Choosing a ready-made dimmer

If you decide to purchase a factory-made dimmer, pay attention to the following:

Specifications

There are only two of them:

• network voltage;
• permissible load power.

For example, for a chandelier with three conventional 100 W incandescent lamps, a dimmer with 230 V / (25 - 400 W) characteristics is suitable. Permissible power is always indicated as a certain range, the upper value of which should be taken with some margin.

Note! For some Chinese dimmers, for example, from Powerman, an interesting feature was noticed: one power value is indicated on the label, and another on the device case. Moreover, these values ​​\u200b\u200bcan be quite different, for example, they write “600 W” on the label, and “25 - 400 W” on the case.

Therefore, when buying a cheap imported dimmer, do not limit yourself to studying the information given on the box - be sure to consider the device itself.

Load type

The simplest dimmers are designed to control the power of incandescent and halogen lamps.

Rotary dimmer for incandescent lamps

More advanced models can also work with low-power electric motors - usually fans are connected through them. An example is the dimmer Kopp Dimmat (Germany).

One of the representatives of the Kopp Dimmat dimmer range

Dimmers are also available through which fluorescent lamps can be connected. If any of the mentioned loads is powered through a simple dimmer, then it may fail.

It is important to know that not every such lamp can be connected to a dimmer designed to connect, say, fluorescent lamps. It should be marked "dimmerable" or, equivalently, "dimable".

Control method

On this basis, dimmers are divided into several varieties:

mechanically controlled

These are the simplest and cheapest devices. They have a rotary handle, which is why they are usually called rotary. An example is the domestic model "Bella C16-65". Rotary dimmers have minimal functionality. To turn off the light, the knob must be turned to its extreme position until it clicks; The inconvenience of this control method is the lack of a function for remembering the settings - the brightness of the lighting has to be re-adjusted every time it is turned on.

Electronically controlled

These dimmers are divided into keyboard and touch. There are also pseudo-touch ones, for example, the Simon 75305-39 model, the keys of which are pressed with such little effort that they almost do not differ from the touch panel.

Touch dimmer for LED lamps

Typically, keys and touchpads have a dual effect: a short press / touch turns the light on or off, and a long hold changes the brightness of the light. When you turn on the lamp, the brightness will immediately be the same as it was set before turning it off, that is, you no longer need to adjust the light every time.

Note! Along with the usual ones, dimmers are produced, which, when the lamp is turned on, supply voltage to it with a smooth increase. It is believed that such dimmers prolong the life of the lamps.

An example of a touch-controlled dimmer is the SM180 model by Eunea Merlin Gerin (Spain). In addition to conventional lamps (incandescent and halogen lamps for 230 V), low-voltage halogen lamps with a conventional (ferromagnetic) transformer can be connected through this regulator.

with remote control

Control signals can be transmitted both by means of infrared (IR) radiation and by means of radio frequency. For example, the Smart Dimmer Pro 21 model of the French company Legrand is equipped with an IR receiver.

Model Smart Dimmer Pro 21

You can connect to it:

• low-voltage halogen lamps not only with conventional, but also with electronic transformers;
• fluorescent lamps with electronic control gear.

The ability to work with such loads is due to the presence of a phase cutoff switch on the leading / trailing edge.

Total power - up to 500 watts.

The remote control can be used not only branded, but also any other with support for the RC5 code.

with sound control

These devices can respond to clapping or even voice commands.

This material will help to independently connect the cotton switch:

Options

Many of the modern dimmers are equipped with an additional terminal to which conventional pushbutton switches can be connected. With their help, you can control the lighting in the room from several places.

There are models equipped with a timer, for example, the already mentioned Simon 75305-39 pseudo-touch dimmer.

Pseudo-touch dimmer Simon 75305–39

After the time set by the user, the device will automatically turn off the light.

The widest range of possibilities is provided by programmable dimmers equipped with a microcontroller. They may have the following features:

• imitation of the presence of residents (automatic switching on and off of the light in order to mislead apartment thieves watching the windows);
• brightness control in various modes, for example, flashing at a certain frequency (Strobe);
• control of several groups of lamps (zones) and memorization of different lighting scenes for them.

An illustrative example of a programmable dimmer is the Lutron Grafik EyeE system (USA).

Dimmer Lutron Grafik EyeE

This is how its multi-zone manifests itself: the user can connect several groups (up to 6) to the system, for example, a chandelier, wall lamps and decorative lights, and then set some brightness value for them for different occasions.

For example, when the family gathers at the festive table, the brightness of the chandelier is set to 70%, and the brightness of wall and decorative light sources is set to 20%. To watch TV, another scene is set up: the brightness of the chandelier is reduced to 20%, the brightness of other lamps is increased to 30%.

The settings of all lighting scenes (their maximum number is 16) are stored in the system's memory, so you can easily switch between them - both quickly and smoothly (the process of switching from one scene to another can be stretched for an hour).

The Grafik EYE system can be controlled with a remote control, it can only work with incandescent lamps.

The maximum total load power is 2300 W, while the maximum for each zone is also specified - no more than 800 W. The capabilities of the system can be expanded by connecting a power amplifier to it. Then the limit for each zone will increase to 1800 watts.

Programmable dimmers are also produced in the CIS countries. For example, the model "Sapphire 2503" of the Belarusian company "Nootekhnika" supports the presence simulation mode and has a timer that turns off the lighting after 12 hours from the moment of the last user action. The dimmer has a touch panel and can be controlled by a remote control. The current to the load when turned on is supplied incrementally (which prolongs the life of the lamps).

Read the product data sheet carefully. Some dimmers heat up noticeably, so manufacturers prescribe their use with restrictions. So, for example, the Dimmat dimmer of the German company Kopp is not recommended to be turned on with a load of more than 300 W if the room temperature exceeds + 25 ° C: but the maximum allowable power declared in its characteristics is 400 W.

Such requirements should be considered with particular attention if the wall on which the device is to be fixed is made of materials with low thermal conductivity, such as wood or drywall.

You should be aware that the efficiency of a light bulb “screwed” with a dimmer is greatly reduced. Therefore, in the event that you have to operate the lamp most of the time in a reduced brightness mode, it is more advisable to replace it with a less powerful one and use the latter without a dimmer.

The most "tenacious" are domestic rotary dimmers. So, for example, the Bella C16-65 model already mentioned is capable of operating with voltage surges from 60 to 285 V.

All modern dimmers have a fuse installed, so it makes sense to get at least one spare in advance.

Note! When the power of a fast-acting light source, such as an LED strip or a gas discharge lamp, is reduced with the help, a stroboscopic effect takes place. In such lighting, moving or rotating mechanisms and tools may appear stationary, which is very traumatic. Therefore, dimmers should be used with caution in workshops and production areas.

How to connect a dimmer

In the general case, the dimmer is connected like a conventional switch, but there is a condition: the regulator must be turned on only in a phase break (switches can be set both in phase and in “zero”).

In practice, dimmers are often installed in pairs or with switches.

Dimmers are connected like switches. Both of these elements are mounted in series with the load. The dimmer can be safely put in place of a conventional switch. To do this, turn off the mains power, disconnect the wires from the terminals of the old switch, and install a dimmer in its place. This operation is also simplified by the fact that the mounting dimensions of the dimmers correspond to the dimensions of simple switches.

Schematic diagram of connecting a dimmer

When connecting a dimmer to the mains, remember: it must be included in the break of the phase (L), and not the neutral (N) wire.

Circuit with a switch

Such schemes are extremely convenient: they allow you to control the intensity of lighting from anywhere in the apartment. In the bedroom. For example, it is advisable to install a dimmer next to the bed - in this case, the user does not have to leave a warm bed to reduce or increase the light intensity.

Connection diagram for a dimmer with a switch

Such a scheme is appropriate to apply in "smart home" systems. Effective light control allows you to highlight individual areas of the room or interior details. A simple switch is installed near the interior door. They are used when entering and leaving the room - when you need to turn the light on or off.

Installation diagram with two dimmers

If necessary, you can adjust the light intensity from two points. in this case, two dimmers are installed, and their first and second terminals are connected to each other. A phase wire is connected to the third terminal of any of the dimmers.

Wiring diagram with two dimmers

The wire to the load comes from the third terminal of the remaining dimmer. As a result of such manipulations, three wires should come out of the junction box of each of the dimmers.

Turning on a dimmer with two pass-through switches

The principle of operation of this scheme is as follows: one switch is installed at the entrance to the room, the second - at the other end of the stairs or corridor. In this case, the dimmer is mounted between the switch and the load in the phase wire.

Connection diagram for a dimmer with two pass-through switches

A dimmer cannot be installed between the walk-through switches.

Please note that if the dimmer in this circuit is turned off, none of the walk-through switches will work.

Connecting a dimmer to LED strips and lamps

If you connect a dimmer to the LED strip, it will be possible to change the brightness of its glow. Choose a dimmer according to the total power of the LED strips.

When implementing this scheme with single-color tapes, a power supply is connected to a dimmer. The outputs of the dimmer are connected to the load itself, while observing the polarity of the current.

In the case of using LED strips with RGB channels, the dimmer is also connected to the power supply, and its outputs to the signal controller.

The power of the dimmer in any of the above cases should be 20–30% higher than the calculated power consumption of the tapes.

Please note: special dimmers are available for working with LED lamps and tapes.

Video: how to replace a switch with a dimmer

Dimmers are very popular, and this encourages manufacturers to actively develop this branch of instrumentation. By now, we have learned how to make regulators for any type of load, including those with transformer power supplies. But if we talk about conventional incandescent or 220 V halogen lamps, then the dimmer for them is an extremely simple device and, as the reader could see, it is quite easy to do it yourself.

What is the point of assembling a dimmer yourself if the modern market for electrical appliances is overflowing with a wide variety of lamp dimmers? After all, it is much easier to purchase a ready-made device than to learn the basics of amateur radio. However, this is not always fair. For example, I wanted to equip the table lamp described earlier in the article - "" with a dimmer. Having walked around the shops selling switches, sockets, various electrical goods, among a significant variety, I could not find a dimmer of the required size, allowing me to "shove" it into a table lamp. As a result, it was decided to assemble a dimmer with your own hands.

On the Internet, it was not possible to find information regarding the hand-made manufacture of the regulator in the required volume. Although I still found the basic information, I managed to find the simplest circuit of this device that fully meets my requirements. I emphasize that this circuit is very simple - everyone, even a person far from electronics, can cope with its assembly.

Attention, the pin assignment is valid when using the triac BT134. If another is used, then the pin assignment will be correspondingly different (the pin assignment of one or another triac can be found on the Internet).

The key elements of the selected circuit are the triac and dinistor. I will not delve into what these details are and what are the features of their work, since the article is not aimed at experienced radio amateurs, but at several masters far from this.

A few words about the principle of operation of the circuit. In order for the lamp (load) to light up, it is necessary that an electric current passes through the triac. This will happen when a voltage of a certain value appears between the electrodes of the triac.

An electric current passing through a variable resistor charges the capacitor. When the voltage on the capacitor reaches a certain value, the triac will open and the light will light up accordingly. Less resistance of the variable resistor - a higher voltage will be applied to the lamp, respectively, the brightness of its glow will be greater.

DIY dimmer - radio components

It was mentioned above that the main elements of the lamp dimmer are the triac and dinistor. I used BT134 (700V) and DB3 respectively. The rest of the details: a non-polar capacitor with a capacity of 0.1-0.22 microfarads (250 V), a resistor - 10 kOhm (withstanding power - 0.25-2 W), a variable resistor - any small-sized resistance of 470-500 kOhm.

I note that if you are not very versed in electronics, I advise you to simply rewrite the list of parts on a piece of paper and go to the radio store with it. I'm sure the salesman who works there knows a lot about radio components and will be able to help you.

If any parts are not available, then they can be replaced by the following analogues:

We carry out the installation of a dimmer

To work, you will need the following tools and materials:

• wire cutters;
• soldering iron;
• solder;
• rosin;
• pieces of wire;
• insulating tape.

Parts purchased, tools and materials prepared - you can start assembling. For convenience, we redraw the diagram on a sheet. We service the conclusions of the radioelements, solder pieces of wire to them (you can take any wire, for example, with a cross section of 1mm 2). After that, we connect the radio elements to each other according to the scheme. To eliminate installation errors, we cross out each finished connection on the redrawn diagram.

I suggest watching a short video that demonstrates my "creation" and its performance.

Agree, sometimes there is a need to adjust the brightness of the lamp. Well, indeed, it is not always required that it shine at full power. If in the evening you gathered with your family in the hall room for a conversation, subdued lighting is enough. Why turn on the chandelier at full power, drive extra kilowatt-hours and overpay for electricity consumption. In this case, the dimmer comes to the rescue, otherwise this device is called a dimmer. With it, you can change the electric power of the lamp and thereby adjust the brightness of the light. Many men, experts in electrical engineering and lovers of radio electronics, assemble a dimmer with their own hands.

But here a completely logical question arises, why do you need a homemade dimmer if you can go to an electrical goods store and buy a factory device? Firstly, the price of a factory regulator, frankly, is not small. But that's half the trouble. Sometimes there is a need to install a dimmer, for example, for a table lamp. And if you go to the store, then it’s not a fact that you will find a device of the right size for you so that you can shove it into such a lighting fixture. So the problem, to assemble a dimmer at home with your own hands, is still relevant and therefore we will devote this article to it.

The main purpose and essence of the dimmer

A few words about what a dimmer is and why is it needed at all?

This device is electronic, designed to use it to change the electrical power. Most often, in this way they change the brightness of lighting devices. Works with incandescent and LED lamps.

The electrical network supplies a current that has a sinusoidal shape. In order for the light bulb to change its brightness, a cut-off sine wave is required to be applied to it. It is possible to cut off the leading or trailing front of the wave due to the thyristors installed in the dimmer circuit. This helps to reduce the voltage supplied to the lamp, which accordingly leads to a decrease in power and brightness of the light.

Important to remember! Such regulators generate electromagnetic interference. To reduce them, an inductive-capacitive filter or a choke is included in the dimmer circuit.

Circuit elements

Let's start by deciding what elements we need for the lighting dimmer circuit.

In fact, the schemes are quite simple and will not require any scarce details; even a not very experienced radio amateur can deal with them.

1. Triac. This is a triode symmetrical thyristor, otherwise it is also called a triac (the name came from the English language). It is a semiconductor device, which is a thyristor variety. It is used for switching operations in 220 V electrical circuits. The triac has two main power outputs, to which the load is connected in series. When the triac is closed, there is no conduction in it and the load turns off. As soon as an unlocking signal is applied to it, conduction appears between its electrodes and the load is turned on. Its main characteristic is the holding current. As long as a current exceeding this value flows through its electrodes, the triac remains open.
2. Dinistor. It belongs to semiconductor devices, is a kind of thyristor, and has bidirectional conductivity. If we consider the principle of its operation in more detail, then the dinistor is two diodes that are connected towards each other. Dinistor is also called diac in another way.
3. Diode. This is an electronic element, which, depending on which direction the electric current takes, has different conductivity. It has two electrodes - a cathode and an anode. When a forward voltage is applied to the diode, it is open; in the case of reverse voltage, the diode is closed.
4. non-polar capacitor. Their main difference from other capacitors is that they can be connected to an electrical circuit without observing polarity. Polarity reversal is allowed during operation.
5. Fixed and variable resistors. In electrical circuits, they are considered a passive element. A fixed resistor has a certain resistance; for a variable, this value can change. Their main purpose is to convert current into voltage or vice versa voltage into current, absorb electrical energy, limit current. A variable resistor is also called a potentiometer, it has a movable output contact, the so-called engine.
6. LED for indicator. This is a semiconductor device that has an electron-hole transition. When an electric current is passed through it in the forward direction, it creates optical radiation.

The triac dimmer circuit uses a phase adjustment method. In this case, the triac is the main regulatory element, the load power that can be connected to this circuit depends on its parameters. For example, if you use a triac VT 12-600, then you can adjust the load power up to 1 kW. If you want to make your dimmer for a more powerful load, then choose a triac with large parameters accordingly.

Principle of operation

Before you make a dimmer with your own hands, let's figure out what the essence of his work is.

• When the circuit is connected to an electrical circuit, it receives an alternating voltage of 220 V from the network. When a positive half-cycle occurs in the voltage sinusoid, current begins to flow through the resistors and one of the diodes, due to which the capacitor is charged.
• As soon as the voltage reaches the parameter necessary for the breakdown of the dinistor, current begins to flow through the dinistor and through the control electrode of the triac.
• This current contributes to the fact that the triac opens. Lamps that are connected in series with it are connected to the circuit and ignite.
• As soon as the voltage sine wave passes through zero, the triac will close.
• When the voltage sine wave reaches a negative half cycle, the whole process repeats in a similar way.
• The moment of opening the triac has a directly proportional dependence on the value of the active resistance in the circuit. By changing this resistance, it is possible to change the triac opening time in each half-cycle. Thus, the power consumption of the light bulb and the brightness of its glow will smoothly change.

The principle of operation and the subsequent assembly of the device are described in more detail in this video:

Circuit Assembly

Now we come to putting together our dimmer. Keep in mind that the circuit can be mounted, that is, using connecting wires. But it will be better to use a PCB. For this purpose, you can take foil textolite (35x25 mm will be enough). The dimmer, assembled on a triac using a printed circuit board, allows you to minimize the size of the block, it will have small dimensions, and this makes it possible to install it in place of a conventional switch.

Before starting work, stock up on rosin, solder, a soldering iron, wire cutters and connecting wires.

1. Draw the connection diagrams on the board. Drill holes for connecting elements. Using nitro paint, draw tracks on the diagram, and also determine the location of the mounting pads for soldering.
2. Next, the board must be etched. Prepare a solution of ferric chloride. Take the dishes so that the board does not lie tightly on the bottom, but with its corners, as it were, rests against its walls. During etching, turn the board over periodically and stir the solution. In the case when this needs to be done quickly, warm the solution to a temperature of 50-60 degrees.
3. The next step is tinning the board and washing it with alcohol (it is undesirable to use acetone).
4. Install the elements in the holes made, cut off the excess ends and solder all the contacts with a soldering iron.
5. Solder the potentiometer using the connecting wires.
6. And now the assembled dimmer circuit is being tested for incandescent lamps.
7. Connect the light bulb, turn on the circuit in the electrical network and turn the potentiometer knob. If everything is assembled correctly, then the brightness of the lamp should change.

Connection

As a rule, dimmers are installed in place of switches. That is, it is mounted on a phase break in series with the load. This, by the way, is very important, as well as when connecting the switch. In no case do not confuse the phase and zero, if you set the dimmer to break zero, the electronic circuit will fail. In order to avoid mistakes, before installing with an indicator screwdriver, make sure exactly where you have a phase and where is zero.

1. De-energize the workplace by turning off the introductory machine for a room or apartment.
2. Remove the switch from the mounting box.
3. Apply voltage and accurately determine the phase and zero on the disconnected wires. Mark the detected phase in some way (with a marker or electrical tape).
4. Turn off the input power again. Connect the input terminals of the dimmer to the phase wire, the output terminals are connected to the load. For factory regulators, the terminals are marked, in this case it is necessary to connect according to the marking. But for dimmers there is no fundamental difference, so the phase connection can be arbitrary.
5. A do-it-yourself dimmer for 220 V LED lamps is installed in the same way. The only fundamental difference is that it must be installed in front of the controller of these lamps. That is, the output from the dimmer goes to the input of the controller.

The dimmer that you have assembled with your own hands can be used not only as a power regulator on a triac for lighting. With it, you can change the speed of the exhaust fan or adjust the temperature of the soldering tip. So if you are friends with radio electronics, you are quite capable of making a triac controller. It may not make your life much easier, but the fact that you created it yourself is already good.

The main function of the proposed circuit is to adjust the brightness of the glow of incandescent lamps powered by a 220V power supply. The PCB is designed to fit in a junction box, replacing the standard light switch.

Without an additional radiator, the circuit can drive a load of up to 200 W, and in the case of additional cooling, the lamp power depends mainly only on the allowable current of the triac used.

Dimming incandescent lamps is not the only application of this device. It can also be used to smoothly control the power of other AC consumers, as well as to control the power of collector motors (for example, drills, grinders). The scheme can lead to significant savings in electricity consumption.

Characteristics of a dimmer for an incandescent lamp

Adjusting the power of AC consumers is not an easy task. The simplest, but at the same time the least effective way is to use a resistance connected in series with the load. However, in this case, smooth power adjustment is practically impossible in this case.

Previously, a special case of this method of regulation was the inclusion of a thermistor in series with a low-power incandescent lamp, for example, a night lamp. In this case, high power thermistors were used, which are used in tube TVs to protect the filaments from damage at the moment the power is turned on. This was a pretty attractive solution, but these thermistors are hard to come by these days.

Another, perhaps the best method for regulating the power of a 220V load is the use of an autotransformer (LATR). This solution is practically devoid of disadvantages, with the exception of two: the high cost of the autotransformer and its large size. But the huge advantage of using the so-called autotransformers is to obtain an unchanged sinusoidal signal at the output and the ability to increase or decrease the voltage.

The autotransformer, the diagram of which can be seen in the figure below, is an invaluable tool in the radio amateur's workshop. It allows you to test devices powered by the mains and check their resistance to power surges.

We will consider a cheap and simple circuit that works on the principle of phase regulation. As you can see, the circuit is very simple and consists of only a few elements. The most interesting of these is (Diac). The use of this particular element made it possible to develop a simple circuit.

The principle of operation of the dinistor is as follows: it does not conduct current until the voltage on it is below a certain threshold value, usually 12 ... 20V. However, if this voltage is exceeded, the dinistor begins to conduct current until the voltage drops to a value close to zero. The second, very important feature of the diac is the fact that the polarity of the voltage for it does not matter at all, which makes it possible to use this element in AC circuits.

The operation of this useful radio component is best illustrated by the following figure.

Let's now discuss the operation of our dimmer. We will start analyzing its operation at the moment when the mains voltage passes through zero, when the voltage across the capacitor C1 is also close to zero. The voltage in the network begins to rise, charging the capacitor C1 through the resistor R1 and P1.

It is clear that the charge rate depends on the value of the series-connected resistances R1 and P1, and, therefore, using the potentiometer P1, you can change this rate over a wide range.

At some point, the voltage across the capacitor C1 reaches the breakdown value of the dinistor. The dinistor discharges the capacitor through the triac control pin Q1. The triac opens, including the load closes the charge circuit of the capacitor C1 prevents it from recharging.

The next time the voltage passes through zero, the triac turns off, the capacitor C1 starts charging again, and the whole cycle repeats a hundred times per second. It is clear that the less capacitor C1 is charged, the less time the triac will open and, accordingly, less power will go to the load.

In this simple way, we get smooth power control from almost 0 to 99%. The operation of the circuit is best illustrated by the following figure. An additional two elements, inductor D1 and capacitor C2, serve to eliminate a serious drawback of the circuit: the generation of radio interference.

Resistor R2 is added to the circuit (its value must be selected). The purpose of this resistor is to keep the filament of the lamp in a "warm" state. This is a good way to extend the life of incandescent bulbs, which most often burn out the moment they are turned on, because the cold filament has low resistance. When using resistor R2, the current flowing through the lamp is negligible.

Attention. The dimmer is under life-threatening voltage of 220 volts during operation! Installation and adjustment should be carried out only when completely disconnected from the mains. If you are not confident in your abilities, then ask a more experienced specialist for help in assembling this device.