LED dimming circuit. Smooth ignition and decay of LEDs, diagram. Dimmers or dimmers

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:
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?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:

Shrinked the board

VIDEO:

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I T O G:
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I am satisfied with the work done, although I spent quite a lot of time. The process of making boards using the LUT method seemed interesting and uncomplicated to me. But, despite this, in the process of work I probably made all the mistakes that were possible. But, as they say, you learn from mistakes.

Such a board for smooth ignition of LEDs has a fairly wide range of applications and can be used both in a car (smooth ignition of angel eyes, instrument panels, interior lighting, etc.), and in any other place where there are LEDs and a 12V power supply. For example, in illuminating a computer system unit or decorating suspended ceilings.

Brightness control for LED backlighting of car instruments.
Smooth LED ignition circuit.

Many car enthusiasts convert the backlighting of their car’s dashboard from conventional incandescent lamps to LEDs, and often, especially when using super-bright ones, the device shines like a Christmas tree and hurts the eyes with a bright glow, which requires the use of an additional device with which you can adjust the brightness level , as they say, to your taste. In general, there are two methods of regulation, this is analog regulation, which consists of changing the level of constant current of the LED, and PWM regulation, that is, periodically turning on and off the current through the LED for adjustable periods of time. With PWM control, the pulse frequency must be at least 200 Hz, otherwise the flickering of the LEDs will be noticeable to the eye. Below is a schematic diagram of the simplest block implemented on the NE555 timer chip, the domestic analogue of which is KR1006VI1; this chip generates pulse-width control signals.

The brightness level of the backlight is regulated by a variable resistor with a nominal value of 50 kOhm, that is, this resistor changes the duty cycle of the control pulses. An N-channel field-effect transistor IRFZ44N is used as a regulating element, which can be replaced, for example, with an IRF640 or similar.

There is probably no point in making a list of the elements used, there are not so many of them in the circuit, so let’s move on to looking at the printed circuit board.

The printed circuit board was developed in the Sprint Layout program; the type of board in this format looks like this:

Photo view of the PWM controller board LAY6 format:

Many people want to add a smooth ignition effect to the regulator circuit, and a simple circuit widely available on the Internet will help us with this:

On the printed circuit board we placed both of the above circuits, the regulator circuit and the smooth ignition circuit. LAY6 board format looks like this:

Photo view of LAY6 format:

Foil PCB for the board is single-sided, size 24 x 74 mm.

To establish the desired ignition and decay time, play with the values ​​of the resistors indicated on the printed circuit board with asterisks, this time also depends on the value of the electrolytic capacitance in the ignition circuit located above the LED output socket (With an increase in the value of the capacitor, the time will increase).

Please note that the smooth ignition circuit uses a P-channel MOSFET. The pinout of the transistors is shown below:

In addition to the article, we provide another example of a circuit with a brightness control and smooth ignition of LEDs on a car dashboard:

The size of the archive with article materials is 0.4 Mb.

Recently I decided to put together a circuit that would allow me to smoothly light up any LED strip (whether in a car or at home). I didn’t reinvent the wheel, and decided to do a little Google it. When searching on almost every site, I found circuits where the LED load is severely limited by the capabilities of the circuit.

I wanted the circuit to just gradually increase the output voltage, for the diodes to light up smoothly, and for the circuit to be passive (it did not require additional power and would not consume current in standby mode) and would definitely be protected by a voltage stabilizer to increase the lifespan of my backlight .

And since I haven’t learned how to etch boards yet, I decided that first I need to master the simplest circuits and during installation use ready-made circuit boards, which, like the rest of the circuit components, can be purchased at any radio parts store.

In order to assemble a circuit for smooth ignition of LEDs with stabilization, I needed to purchase the following Components:

In general, a ready-made circuit board is a fairly convenient alternative to the so-called “LUT” method, where using the Sprint-Layout program, a printer and the same PCB, you can assemble almost any circuit. So, beginners should still first master a simpler option, which is much simpler and, most importantly, “forgiving of mistakes” and also does not require a soldering station.

Having simplified the original diagram a little, I decided to redraw it:

I know that on the diagrams the transistor and stabilizer are not indicated that way, but it’s easier for me, and it will be clearer for you. And if, like me, you managed to take care of stabilization, then you need an even simpler scheme:

The same thing, only without using the KREN8B stabilizer.

• R3 - 10K Ohm
• R2 - 51K Ohm
• R1 - from 50K to 100K Ohm (the resistance of this resistor can control the speed of LED ignition).
• C1 - from 200 to 400 μF (you can choose other containers, but you should not exceed 1000 μF).

At that time I needed two soft ignition boards:
- for the already made highlighting of the legs.
- for smooth ignition of the dashboard.

Since I had already taken care of stabilizing the LEDs illuminating my legs a long time ago, Krenka was no longer needed in the ignition circuit.

Smooth ignition scheme without stabilizer.

For such a circuit, I used only 1.5 sq cm of circuit board, which costs only 60 rubles.

Smooth ignition circuit with voltage stabilizer.

Dimensions 25 x 10 mm.

The advantages of this circuit are that the connected load depends only on the capabilities of the power supply (car battery), and on the IRF9540N field-effect transistor, which is very reliable (it makes it possible to connect a 140W load through itself at a current of up to 23A (information from the Internet). The circuit can withstand 10 meters of LED strip, but then the transistor will have to be cooled, fortunately in this design you can attach a radiator to the field device (which of course will lead to an increase in the circuit area).

During the first testing of the circuit, a short video was shot:

Initially, R1 was rated at 60K Ohm and I didn’t like the fact that ignition to full brightness took about 5-6 seconds. Subsequently, another 60K Ohm resistor was soldered to R1 and the ignition time decreased to 3 seconds, which was just right for illuminating the legs .

And since the ignition circuit for illuminating the legs had to be connected to a break in the main power circuit, without thinking long about how to insulate it, I simply stuffed it into a piece of the bicycle inner tube.

Having connected the smooth ignition circuit, I made another video:

That's all, I thank all those who were still able to read this post to the end. Of course, for some this will be a tough button accordion, but I hope there will be comrades who will be interested.

In addition to a purely decorative function, for example, illumination of a car showroom, the use of soft switching, or ignition, has a fundamental practical significance for LEDs - a significant extension of service life. Therefore, we will consider how to make a device with your own hands to solve such a problem, whether it is worth making it yourself or is it better to buy a ready-made one, what is required for this, as well as what circuit options are available for amateur production.

The first question that arises when it is necessary to include a soft ignition module for LEDs in the circuit is whether to make it yourself or buy it. Naturally, it is easier to purchase a ready-made block with specified parameters. However, this method of solving the problem has one serious disadvantage - the price. When making it yourself, the cost of such a device will decrease several times. In addition, the assembly process does not take much time. In addition, there are proven options for the device - all that remains is to acquire the necessary components and equipment and connect them correctly, in accordance with the instructions.

Note! LED lighting is widely used in cars. For example, these could be daytime running lights and interior lighting. The inclusion of a smooth ignition block for LED lamps allows, in the first case, to significantly extend the life of the optics, and in the second, to prevent the driver and passengers from being blinded by the sudden switching on of a light bulb in the cabin, which makes the lighting system more visually comfortable.

What do you need

To properly assemble a soft ignition module for LEDs, you will need a set of the following tools and materials:

1. Soldering station and set of consumables (solder, flux, etc.).
2. A fragment of a textolite sheet for creating a board.
3. Housing for placing components.
4. The necessary semiconductor elements are transistors, resistors, capacitors, diodes, ice crystals.

However, before you start making your own soft start/damping unit for LEDs, you need to familiarize yourself with the principle of its operation.

The image shows a diagram of the simplest model of the device:

It has three working elements:

1. Resistor (R).
2. Capacitor module (C).
3. LED (HL).

A resistor-capacitor circuit based on the RC delay principle essentially controls the ignition parameters. So, the greater the value of resistance and capacitance, the longer the period or the smoother the switching on of the ice element occurs, and vice versa.

Recommendation! At the moment, a huge number of soft ignition block circuits for 12V LEDs have been developed. They all differ in their characteristic set of pros, cons, level of complexity and quality. There is no reason to independently manufacture devices with extensive circuit boards using expensive components. The easiest way is to make a module on one transistor with a small connection, sufficient for slow turning on and off of an ice light bulb.

Schemes for smooth switching on and off of LEDs

There are two popular and self-manufacturing options for soft ignition circuits for LEDs:

1. The simplest.
2. With function for setting the start period.

Read also Dynamic monitor backlight: characteristics, diagram, settings

Let's consider what elements they consist of, what is the algorithm of their operation and the main features.

A simple scheme for smoothly turning on and off LEDs

Only at first glance, the smooth ignition diagram presented below may seem simplified. In fact, it is very reliable, inexpensive and has many advantages.

It is based on the following components:

1. IRF540 is a field-effect transistor (VT1).
2. Capacitive capacitor 220 mF, rated at 16 volts (C1).
3. A chain of resistors of 12, 22 and 40 kiloOhms (R1, R2, R3).
4. Led crystal.

The device operates from a 12 V DC power supply according to the following principle:

1. When the circuit is energized, current begins to flow through block R2.
2. Thanks to this, element C1 is gradually charged (the capacity rating increases), which in turn contributes to the slow opening of the VT module.
3. The increasing potential at pin 1 (field gate) provokes the flow of current through R1, which contributes to the gradual opening of pin 2 (VT drain).
4. As a result, the current passes to the source of the field unit and to the load and ensures smooth ignition of the LED.

The process of extinction of the ice element follows the reverse principle - after removing the power (opening the “control plus”). In this case, the capacitor module, gradually discharging, transfers the capacitance potential to blocks R1 and R2. The speed of the process is regulated by the rating of the element R3.

The main element in the smooth ignition system for LEDs is the MOSFET IRF540 n-channel field-effect transistor (as an option, you can use the Russian model KP540).

The remaining components relate to the harness and are of secondary importance. Therefore, it would be useful to present its main parameters here:

1. Drain current is within 23A.
2. The polarity value is n.
3. Drain-source voltage rating is 100V.

Important! Due to the fact that the speed of ignition and attenuation of the LED depends entirely on the value of resistance R3, you can select the required value to set a certain time for the soft start and shutdown of the ice lamp. In this case, the selection rule is simple - the higher the resistance, the longer the ignition, and vice versa.

Improved version with the ability to customize the time

Often there is a need to change the period of smooth ignition of LEDs. The scheme discussed above does not provide such an opportunity. Therefore, it is necessary to introduce two more semiconductor components into it - R4 and R5. With their help, you can set resistance parameters and thereby control the ignition speed of the diodes.

For beautiful illumination of individual car parts, backlights, instrument panels, side lights. It turns out to be a rather interesting effect, in which you turn off the power to an illuminated object, and it gradually fades out within 5 - 10 seconds...

How to implement smooth turning off of LEDs

To implement this, you and I will need the following components:

1. Actually the LED.
2. Capacitor (electrolytic, large capacity).
3. Diode.
4. Resistor if using 3.5 V LEDs.
5. Soldering iron, tin, flux.

Let's start with the object. Where can I put it? Well, it all depends on your imagination. Side lights, interior lights, instrument lighting - and many other places where you can insert a smoothly switching LED. I will soon implement a smooth switch-off of the interior lamp, that is, so that when the doors are closed it will remain on for some time. Also, if you make, in combination with them it will not turn out bad.

Well, let's begin. The purpose of all the elements, I think, is clear, but it wouldn’t hurt to repeat it. The LED is needed to emit light waves :). The capacitor is this element that stores the voltage that is consumed when the power is turned off. A diode is used to prevent current from flowing to other consumers, in other words, it acts as a kind of valve (it lets it go there, but not back).

Manufacturing of smoothly extinguishing LEDs

I’ll sketch out this intuitive diagram:

In the diagram we see that there is nothing complicated. So let's grab the soldering iron and go ahead. I will make a reservation that you need to find out how to accurately connect the components. Electrolytic capacitors have the ability to fly apart with a shot! So take a close look at the photo:

It is also important to connect the diode correctly:

Well, we seem to have sorted it out. As for the ratings of the parts, almost any diode will do, since the current is small. Capacitor – we select the capacitance individually; the larger the capacitance, the longer the LED lights up after the power is turned off. The voltage across the capacitor is at least 16V.