All About LED Dimmers

- Feb 01, 2018-

Dimming from the English language is translated only as "blackout." What is a dimmer, what they are and where else can be applied we will tell in this article. From the sources and to the final realization. The most important question is whether to use LED lamps with a dimmer?

Dimmer for LED lamps

What is a dimmer and why is it needed?

Dimmer is an electronic device capable of regulating power, by controlling the voltage applied to the load. The definition is very dry and boring, let's explain the principle of action in a more simple language.

The power depends on the voltage and current in the load. This means that if one of the components is reduced, the power also decreases. Voltage and current are connected by Ohm's law, which means you can reduce the power of your device (luminaire brightness) by increasing the overall load resistance. That is, use ballast resistors, chokes or capacitors.

Ballast power dampers - convert excess energy into heat and have low efficiency. To adjust the power of the device, in our case the brightness of the light bulb, you need another device - a dimmer.

Is it possible to connect the LED lamps through the dimmer? Can. But not everyone will be steadily regulated. Here you need special LED lamps for dimmer.

LED lamps, adjustable with a dimmer , are  suitable for work with any regulator. But there are some nuances in contrast to the type of voltage regulation. This is determined by the dimmer circuitry, the differences will be described in detail in the following sections of the article. The type of dimmer depends on how well the LED is regulated.

Which LED lamps can be used with a dimmer? In this issue everything is extremely individual. Everything depends both on the circuit of the light bulb itself and on the regulator's schematic. In the general case, the so-called dimmable LED lamps perfectly match  .

What are dimmers?

Power regulators can be divided into two large groups:

  • For operation in alternating voltage circuits (220V);

  • for operation in DC circuits (for a 12V LED strip).

In drills also need a regulator, to adjust the speed, it is located in the button.

Dimir in the electric drill

It can be used for various purposes, in this list they are located by popularity:

  1. Adjustment of brightness of light, dimming of LED and incandescent lamps;

  2. adjustment of the temperature of the fan in different heaters;

  3. rotation control of the collector motor.

What are the differences between dimmers?

If you are going to use a switch with brightness adjustment, you first need to find out what they are. And in general, can all LED lamps be dimmed?

Dimmers differ in the following criteria:

  • By type of installation;

  • on execution and method of management;

  • by the method of regulation.

Let's look at the details of each of them.

By type of installation

For outdoor installation - surface- mounted switch with dimmer for LED lamps. To install such a device, you do not need to drill a niche in the wall, it simply mounts on top of the wall. It is very convenient to use in cases where the interior is not in priority or laid outdoor cabling.

Overhead dimmer

For internal installation - perfectly fit into any interior, such as this one.

Dimmer for indoor installation

For DIN rail mounting, they are very specific and at first it may seem that they are not practical. However, this light control for LED lamps works with the remote control, while it is hidden from prying eyes in the electrical panel.

Dimmer on DIN rail

On execution

By design, the dimmer for LED and incandescent lamps can be:

  • Turning;

  • rotary-push type;

  • button;

  • sensory;

Rotary - one of the simplest options for the brightness control of the LED lamp, looks unpretentious, has the simplest functionality.

Rotary dimmer

Turn-push looks almost the same as the swivel. Due to its design, when you press it, the light with the brightness that was set at the last turn on lights up.

Rotary-type dimmer type

Pushbutton regulator for LED lighting looks more technologically and organically fit into a modern apartment. Such as this switch with dimmer control for LED lamps.

Pushbutton dimmer

Sensory models and can be completely different - from luminous circles to smooth single-color panels for adjusting the voltage of LED lamps.

Sensor type dimmer

By the way of adjustment

Dimmers are different not only in their execution, but also in accordance with the principle of work. E then deals specifically with the AC dimmers.

The first type dimmers more common and cheap, because of the simplicity of their scheme - this is dimmer with a cut-off on the rising edge (Eng. A leading edge ). A little further will be considered in detail its operation principle and circuit, for comparison, take a look at the type of voltage at the output of such a controller.

Voltage circuit on the leading edge

The graph shows that the load is fed the remainder of the half-wave, and its beginning is cut off. Due to the nature of the load, electric networks are interfered with, which hinders the operation of televisions and other devices. The lamp is supplied with a voltage of the set amplitude, and then it attenuates when the sine wave passes through zero.

Can I use the leading edge dimmer for diode lamps? Can. LED lamps with a dimmer of this type will be easily adjustable, only if they are originally designed for this. This is evidenced by the symbols on its packaging. They are also called "dimmable".

The second type works differently, producing less noise and works best with different bulbs - a dimmer with a cut-off trailing edge (Eng. Falling edge ).

The graph of the voltage by the principle of falling edge

Adjustment of LED lamps with dimmers of this type is better, and its design better supports non-dimming light sources. The only drawback is that these lamps can adjust their brightness not from "zero", but in a certain range. At the same dimmable LED lamps - just perfectly adjustable.

The best solution is to use a Falling Edge dimmer for LED lights.

A separate word can be said about ready-made LED luminaires with brightness adjustment. This is a separate class of lighting devices that do not require the installation of additional regulators, but have it in their design. Their adjustments are made using the buttons on the case or from the console.

Ready luminaires with brightness adjustment

Schemes of dimmers

The dimmer for voltage 220V, with cutoff on the leading edge, operates on the principle of phase-impulse voltage control. During operation, the elements of such a dimmer apply voltage to the load at certain times, cutting off a part of the sinusoid. This is shown in more detail and graphically on the graphs.

Voltage graph leading edge

The area of the sinusoidal shaded in gray is the area of the voltage or its effective value that is supplied to the load (lamp or any other device described above).

The red dashed line shows the shape of the voltage at the dimmer input for the led lamps. In this form it is fed through a conventional switch without adjustments .

How to connect the LEDs through the dimmer?

The simplest power controller on triac

Component ratings and all information are shown on the dimmer diagram.

The device is installed in the break of the wire going to the light source, the motor, the tenon or any other device.

The logic of the circuit is as follows: capacitor C1 is charged through the chain R1 and potentiometer R2. Depending on the position of the potentiometer, the capacitor is charged up to the opening voltage of the VD1 diode.

The circuit used DB3 dinistor, this is approximately 30V. An open biasing pulse is applied to control the opening pulse of the triac (bidirectional thyristor) to its control electrode.

The greater the resistance exhibited by the potentiometer's knob, the longer the capacitor is charged, the later the dinistor-triac chain will open, and the voltage will be lower, since the greater part of the sinusoid will be cut off. And vice versa - less resistance - more voltage at the output of the regulator.

Scheme and model of voltage regulator

On the Internet, there are many options for schemes with all sorts of improvements, they are all good. Here is a simple diagram, the figure shows the installation of this version of the circuit.

How to adjust the illumination of LED

What kind of bulbs can I use with a dimmer? When lighting was mainly used for incandescent lamps, everything was simple - a normal dimmer easily coped with the adjustment of brightness.

The incandescent lamps were replaced by energy-saving luminescent housekeepers, they could not be regulated at all. Of course, there were electronic ballasts for tubular fluorescent light bulbs with the possibility of dimming, but extremely rarely and they cost dearly.

Now energy-saving lamps are replaced by LED lamps. The process of emission of photons of light, although difficult, but from the point of view of regulation, perhaps, is simpler than adjustment of gas-discharge light sources.

Dimmable LED bulbs - what is it?

What is a dimmable LED lamp? This is a light bulb that can be adjusted by brightness with the help of ANY dimmer, which is designed for alternating or direct current (depending on the type).

In its power scheme, the brightness change functions are incorporated, depending on the supply voltage. Dimmable LED lamps work with dimmer circuits like the one shown above.

The mains dimmer adjusts the supply voltage. This means that for any voltage values, at a range specified by the manufacturer (it is indicated on the box from the light bulb), the lamp circuit will tend to maintain the specified current. The brightness in turn depends on the current.

Normal LED lamps can not be adjusted, at best it will simply turn on and off, at worst it will burn at low values set on the dimmer.

In the cheapest LED lamps there is a damping capacitor. If they are regulated, then only in very narrow limits, so they also do not fit. Example of dimming conventional LED light bulbs look at the video.

Dimmable LED bulbs for 220 volts

Adjusting the brightness of the LED lamps to 220V is difficult, because there is a current stabilization scheme installed on a specialized driver. Its task is to stabilize the output current, to ensure a uniform and long glow of the LEDs, regardless of the voltage of the mains.

Ordinary LED lamps are not very amenable to dimming. To select the correct Led dimmer lamp - you need to carefully study the description and the symbols on the box and the lamp housing.

Examples of dimming possibilities

LED dimming lamps can be recognized by the inscription: "for a dimmer," "adjustable" or something like that, you can just draw a conditional image of the dimmer, as in the examples below.

Is it possible to adjust the brightness of LED lamps powered by DC?

On the photo led dimmer for 12V LED strip. Let's see how this dimmer works with LED lamps.

Dimmer for constant voltage

For direct current circuits, the operating principle of the controller is different. Here, a bipolar or field-effect transistor is used as a metering element, and a pulse generator with a variable duty cycle is used as a metering device.

The method of this control is called Pulse Width Modulation (PWM). To understand how this works you need to familiarize yourself with the charts.

PWM operation principle

Vcc is the voltage at the input of the DC dimmer, V is the output voltage. You can see how the average voltage changes. As the pulse width is increased and the pause length is shortened (increasing the duty cycle), the output voltage increases.

Schematic diagram of PWM controller

Above is a schematic circuit diagram of the "PWM dimmer control led lamps for NE555". It can act as a device for dimming LEDs. Works as follows:

NE555 is a timer connected here in the pulse generator mode, the frequency and duration of which is set by the RC circuit consisting of R2, the potentiometer R1 and the capacitor C5, as in the previous scheme the potentiometer regulates the charge speed of the capacitor, in accordance with the charge rate, the pulse width is formed.

Initially, the circuit produces symmetrical pulses, that is, the length of the pause is equal to the length of the pulse. But thanks to the presence of a potentiometer and a chain of two diodes VD1 and VD2, there is a charge and recharge of the capacitance through different resistances of the potentiometer, or rather through different pairs of its contacts.

Therefore, PWM controlled pulses are formed with a constant frequency, but with a variable duty cycle.

If you use it in a car or dimming an LED strip, you can exclude an additional 9 volt power supply, based on the 7809 linear regulator, and apply power to the first point after it on the circuit.

And here are pictures of the home-made dimmer for LEDs, if necessary - you can draw the location of the tracks and repeat it. Or to collect on a breadboard.

Homemade dimmer for LEDs

A video of how dimming of LED luminaires works with this circuit is shown in the example of the lateral glow ribbon below.

With this circuit, it is possible to dim LED circuits at 12V and any other DC load. For example, adjust the speed of the cooler for PCs, collector motors, heaters, in general everything that you come up with. In one of the articles we have already talked about making an LED dimmer with our own hands .

What dimmer is needed for LED light bulbs?

To select a dimmer for LED lamps and ensure their compatibility, you must first determine which lamps you will use. If you plan to buy 220V LED light bulbs - for this purpose phase-impulse devices are suitable, which were considered at the beginning of the article. Take models with a cutoff on the trailing edge.

For low-voltage direct current lamps (for example 12V, which are used in spotlights, desk lights or car lamps) - any PWM regulator or dimmer for LED strips is suitable. All of them work on the principle of pulse-width modulation, linear regulation is already far in the past.

It is also better to buy special LED lamps under the dimmer. Although they are more expensive, but there will be no problems with their adjustment. You will create the desired lighting solution only if you correctly select the dimmer and LED lamps to it.

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