Not all LED strip can be controlled by dimmers. It would seem that the current-voltage characteristic and a graph of the performance directly hinted at such a possibility, but it is much thinner. Today we will discuss how to connect a dimmer instead of a switch.
How do dimmers
Pre acquaint readers with the operation of the dimmer. Due to which the voltage changes, why is it necessary to the user.
The first voltage regulating device for an electrical load
Since the installation of a dimmer, you need to imagine what happens in the end. It is required to be aware of the principle of the device. So it will be able to predict the consequences. The first attempts to influence the electrical load changes in the supply voltage undertaken in 1896 when Granville Woods changed the output parameters of the current generators. To patent applied image as it is used in practice to control the luminosity of the filament lamps and the engine rotational speed.
Do not say that the text issued by the inventor in a more understandable, but we believe that at the time it looked different. For example, today it is known that the synchronous generator, excited by an alternating current on a par with the constant to get the required parameters. In the early years, according to the explanations Granville, used to stabilize a simple power source (motor or turbine, combusting the fuel). As a result, the inventor believes that forms the DC potential at the generator output. We call the alternating voltage of the fixed voltage and frequency.
As a result of clever manipulation of the resistances was conducted on the impact of the engine. I do not understand the type of motor. I can not say with certainty that in the electric motors used in the United States at the junction of the 19th and 20th centuries. We believe eventually control is based on voltage amplitude change, rather than frequency. At the same time it allows you to control the luminosity of the lamp according to the law Joule: power allocated to active resistance, it depends on the square of the potential difference across its terminals.
Today, many ways of voltage control, the authors do not know how to apply Granville. According to the drawing, the resistance present in the circuit, causing speculation about the creation of a rheostat, also refers to the regulation of the magnetic field that pushes already the idea of changing the parameters of windings, leading to autotransformers (more precisely, the windings with a variable number of active coils) and coils of the variable inductance. As a result, we do not know to what kind of dimmers invention include Granville Woods, but this is certainly the first example of this kind of devices.
Dimmers transformers based on rotating coils
In the 20s of the 20th century used voltage regulators based on transformers with rotating windings. When the angle of inclination of the planes of the two coils is controlled by the induction flux. Due to this, the EMF ranges that are induced in the secondary winding. Using transformer isolation provided by current losses are much lower than in the rheostat.
Autotransformers as dimmers
Commercial versions for home use began to appear much later. The first to be considered autotransformer Joel Spira, applied in the year 1961 as part of a standard electrical panel. The advantage of the solution is considered to be relatively economical. Previously used dimmers based dimmers. To understand the principle of operation, it is required to have an idea of the resistive divider. The load is switched sequentially with the rheostat, the voltage is applied as a result of proportionally. Increasing resistance by the slider, take away some of the power from the load.
As a result, heat is released rheostat mass. Acceptable abbreviate it, increasing the load resistance, the power is proportional to the square of the current (Joule law: P = I x I x R). Even applied liquid rheostat based on salt water. In this case, it served as electrolyte resistance, and the value was changed by varying the distance between the contacts. Dimmers require intense heat to work properly. This makes the use of complex systems, for example, forced air cooling.
Autotransformers were bulky, but here the power is lost is much smaller, because the resistance of the copper winding little. Autotransformer working curiously. Its coil inductance due to the high AC resistance is great, but the imaginary. Part time auto-transformer with no load takes the energy network, then gives. This is called reactive power. She had not spent itself, the effect is considered to be harmful.
The device auto-transformer
But it is necessary to connect the output of something that is fundamentally changing. Autotransformer is arranged, as shown in the figure. There is only one coil, which voltage is generated due to the imaginary impedance and induced EMF. The more windings are involved in the secondary circuit, the higher voltage is transmitted further. And the remaining reactive power goes back into the food chain. Note that the secondary winding no galvanic isolation (current) is missing. Sometimes regarded as a disadvantage.
Such an inductive divider will only operate on alternating current. For a constant resistance is so low that immediately burn or will damage the power supply. The disadvantage of autotransformers is considered a relatively high resolution. But they, like the rheostat, not change of the voltage: the output is similar sine wave with low distortion. In fact, auto-transformer is an analog resistive divider.
Electronic dimmers operate quite differently. In this case, the amplitude is regulated not, as previously, and the average value of the voltage. Part of the period sine wave is cut off thyristor key. One of the schemes presented in the English-language Wikipedia domain, embodied in the figure:
- Thyristor wound circuit to the output line of the rectifier. Here, the voltage has the form of hillocks, closely adjacent (see. picture).
- At the initial time the thyristor is closed. The voltage across the lamp fails.
- Capacitor C1 is charged through the resistor R1, the time constant depends on the product of their denominations (tau = RC).
- At some point in time triggered a zener diode, thyristor opens.
The circuit operation of the electronic dimmer
The faster charging of the capacitor C1, the thyristor switch opens soon, the tension will be held in a light bulb. This changes the cut-off angle, which determines the average voltage level affects the brightness. Voltage becomes a sinusoidal shape (see FIG. picture). By changing the grip resistor, directly affect the constant charge time RC chain. As a result, the cut-off angle is increased or decreased by adjusting the brightness of the light bulb emission in the desired direction.
The whole principle of this equipment is different, the meaning is usually limited to a change in the cut-off angle. In this case, the spectrum of the signal distortion increases, causing adverse effects.
Which to choose dimmer
From the above it is clear that the installation is made simple dimmmera instead of the switch. If the chandelier screwed incandescent bulb, much is happening. the emission spectrum is shifted slightly toward the warm colors, the intensity decreases. Which is explained by a decrease in temperature of the wire. spectrum peak according to Wien's law goes to lower frequencies. When a supply voltage becomes entirely infrared radiation range (from the bulb comes exclusively heat). The effect is used to prolong the life of the filament
- If sharply to light a lamp abrupt temperature change causes deformation of the filament, which leads to rapid failure.
- Advanced dimmers produce a pre-heating coil. Changes to be not as sharp.
- In the preheating takes up 10% of the rated current.
Some dimmers gently for 30 minutes or more to a maximum intensity is raised border. It is understood that the tricks require complex circuits. Dimmers, sparing the life of light bulbs are more expensive.
Bit working on the starter. It is implemented on the basis of the throttle, which is due to the phenomenon of self-induction electromotive force produces a large amount by the cut pulse, when the ballast opens bimetallic relay from heating. Fluorescent lights on dimmers do not work directly. In this case, the starter nedobiraet EMF to ignite the arc. But the devices sold in the store, and equipped with electronic ballast, are not always willing to work with the voltage variable.
Connect the dimmer is often accompanied by the need to revise its illuminations. Lamp, working in a mode of brightness regulation is more expensive than usual. The difference in price is 20%. It is clear that not everyone is willing to pay the amount. Other E27 lamp holder (for example) inside the cap comprise a driver that converts an input voltage to the desired nominal value. The brightness will not change, just the chandelier extinguished at some point.
Dimmer does not hurt the driver light bulbs, but the electronic able to do it. The input voltage range of harmonics appearing in abundance, not designed to work with that device.
Do I need to put a dimmer
Few choose the dimmer, it is necessary to assess its practical side. This device, as above, are now increasingly being built on the electronic circuit with the angle of the cut-off voltage. A simplest implementation, the dimmer brings angle cutoff sinusoid. And the changes directly form the mains current. As a result, local stress becomes unintended harmonics. Dimmer becomes a storm for sensitive electronic equipment. As a result, such devices include bad network voltage through the filter.
The difficulty is that there is such (for DIN-rail) of more than two thousand. It's not the price that is easy to pay, without thinking, given the fact that the costs in the distribution board. In addition, LED lamp, designed to work in tandem with a dimmer, is more expensive than usual.
The correct choice of the dimmer does not eliminate the main thing - the air interference. Without being placed in the display, the unit starts to emit active in a wide range. It is harmful to health. On hearing this, you can check in using the filament bulb: if you put a dimmer on minimum spiral starts barely audible whistle. This means the appearance of the network voltage harmonics spectrum of ultrasound. Dimmer swayed by a kind of thread that is heard whistling.