Revamping the dimmer regulator of cabin lighting
21 September 2011 | Author: Nick | Viewings: 43843 |
If you decide to remake the original interior lighting with regular bulbs on the LED, then you will definitely need this update regulator dimmer salon lights.
Why do I need it?
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This improvement of OEM dimmer is designed for those who changed all the interior lighting of VAZ 2110 for LED (we are talking about the dashboard lighting, air duct lighting, installed speaker lighting, etc.) OEM dimmer is designed to regulate the lighting of regular bulbs and LEDs will not have any effect. Changing the regulator following the example of this article, you will make it possible to regulate the LED backlight, but you will not be able to regulate the backlight of the bulbs.
You can modify your dimmer in one of two ways.
Option 1: Adjusting the LED interior lighting VAZ 2110
You can see the dimensions of the standard and the new one. In the middle is such a mechanism. Choose a drill on the diameter of the knob of the new resistor (in this case 5,5 mm) In the native handle increase the drill hole and insert the new resistor.
I fixed the new resistor this way. Assemble in the reverse order. Solder wiring and put it in the car.
Option 2: Adjusting the diode interior lighting VAZ 2110
Will adjust by means of Shim. Already tried the scheme and design of the add-on to the regular regulator.
In this video you can see how the unit assembled according to this scheme regulates the brightness of the backlight.
Adjusting the brightness of the LED dashboard backlight
Power for the board takes the power from the OEM backlight, ie from the 4th contact of the red strip – soldering a wire directly to the solder pin from the inside of the board. Another thing done is to turn on the backlight when you turn the ignition key. To do this through the diode drags wire from the 2nd contact of the red strip to the 4th contact (white) in the car, after the strip, also hang a diode, so when you turn on the ignition we do not use the whole circuit lights. Why exactly behind the block – so that the ignition would light up the LCD screens of the instrument panel. By the way under these I put a white LED and left the blue light filter
Adjusting the brightness of the LEDs in the car
Brightness adjustment of light sources is used to create a comfortable lighting of the room or place of work. Brightness adjustment is possible device several circuits, which include separate switches. In this case, you get a step change in lighting, as well as separate lights and lights off, which can cause inconvenience.
Stylish and up-to-date designs include smoothly adjusting the overall light intensity as long as all the lamps glow. This allows you to create both an intimate setting for lounging and a bright one for celebrations or working with small details.
Previously, when the main light sources were incandescent bulbs and spotlights with halogen lamps, there were no problems with adjustment. We used a regular 220V dimmer with a triac (or thyristors). This was usually in the form of a switch, with a rotary knob instead of keys.
With the advent of energy-saving (compact fluorescent bulbs) and then LEDs, this approach became impossible. Recently, however, the vast majority of light sources are LED lights and bulbs, and incandescent bulbs are banned for lighting purposes in many countries.
Interestingly enough, the packaging from domestic incandescent bulbs now indicate something like: “Electric heat emitter”.
In this article, you will learn about the principle of dimming LEDs, as well as what it looks like in practice.
Theory
Any semiconductor diode is an electronic device that carries current in one direction. The current flow is not linearly related to the applied voltage, rather it resembles a branch of a parabola. This means that when you apply low voltage to the LED – the current will not flow.
It will only flow when the voltage across the diode exceeds the threshold value. For ordinary rectifier diodes, this is between 0.3V and 0.8V depending on the material of which the diode is made. Silicon diodes take about 0.7V, germanium diodes about 0.3V. Schottky diodes are about 0.3V.
The LED is no exception. The threshold voltage of a white LED is about 3V, in general it depends on the semiconductor it is made of and the color of the LED. The red LED has a voltage of about 1.7V. When this voltage is reached, current will flow and the LED will start to glow. Below you see the volt-ampere characteristic of the LED.
The brightness of the LED depends on the current through it. This is shown in the graph below.
The brightness of an ideal theoretical LED is linearly dependent on current, but in reality things are a bit different. This is due to the differential resistance of the diode and its thermal losses.
An LED is a device that is powered by current, not voltage. Accordingly, to adjust its brightness, you need to change the current strength.
Of course, the current intensity depends on the applied voltage, but as you can judge from the first graph, even a slight change in voltage entails an incommensurable increase in current.
Therefore, dimming with a simple rheostat is a useless task. In such a circuit, if the rheostat resistance decreases, the LED will suddenly light up, and then its brightness will increase slightly, then, with an excessive applied voltage, it will start to warm up a lot and will fail.
Hence the task comes out: Regulate the current at a certain voltage value with a slight change in voltage.
Ways to control the brightness of LEDs: Linear “analog” regulators
The first thing that comes to mind is to use a bipolar transistor because its output current (collector) depends on the input current (base) included in a common collector circuit. We already covered their operation in a great article on bipolar transistors.
You change the base current by changing the voltage drop across the emitter-base junction with potentiometer R2, resistors R1 and R3 are needed to limit the current at maximum open transistor are calculated from the formula:
R=(U-supply-fall on LEDs-fall on transistor)/Ilight.nom.
This circuit I tested, it regulates pretty well current through the LEDs and the brightness of the glow, but noticeable some stepping at certain positions of the potentiometer, possibly due to the fact that the potentiometer was logarithmic, and perhaps because any pn junction of the transistor is the same diode with the same SAC.
A better choice for this task is a current regulated LM317 current regulator circuit, although it is more commonly used as a voltage regulator.
It can also be used to produce a fixed current at a constant voltage. This is especially useful when connecting LEDs to the car’s onboard power system where the voltage is about 11.7V-12V when the engine is idle and reaches 14.7V when the engine is running, a difference of more than 10%. It also works fine when powered from the power supply.
Calculation of output current is simple enough:
It is quite a compact solution:
This method is not very efficient, it depends on the voltage difference between the input of the stabilizer and its output. All voltage is “burned out” on the LM-circuit. The power loss here is determined by the formula:
To improve the efficiency of the regulator, you need a radically different approach – a pulse regulator or PWM regulator.
Ways to control brightness: PWM control
PWM stands for Pulse Width Modulation. It is based on turning the load power on and off at high speed. In this way, we get a change in current through the LED as the full voltage required to open it is applied to it each time. It quickly turns on and off at full brightness, but because of the inertia of vision we don’t notice this and it looks like a decrease in brightness.
With this approach, the light source can give pulsations, it is not recommended to use light sources with pulsations greater than 10%. Detailed values for each type of room are described in SNIP-23-05-95 (or 2010).
Working under pulsating light causes increased fatigue, headaches, and can also cause a stroboscopic effect where rotating parts appear to be stationary. This is unacceptable when working on lathes, drills, etc.
There are a lot of schemes and versions of PWM controllers, so it makes no sense to list them all. The simplest option is to build a PWM controller based on the NE555 timer chip. This is a popular chip. Below you can see a schematic of such a LED dimmer:
But this is actually the same circuit, the difference is that here the power transistor is excluded and it is suitable for regulating 1-2 low-power LEDs with a current of a couple of tens of milliamps. It also does not have a voltage regulator for the 555 chip.
How to adjust the brightness of LED lamps on 220V
The answer is simple: conventional LED lamps are virtually unregulated – that is, not at all. To do this, special dimmable LED lamps are sold, it is written on the packaging or drawn with a dimmer icon.
Perhaps the widest range of dimming LED lamps is represented by GAUSS – different shapes, designs and sockets.
Why can not be dimmed LED lamps 220V
The fact that the power supply circuit of conventional LED lamps is based either on the ballast (capacitor) power supply. Or at the circuit of the simplest pulse step-down converter of the first kind. 220V dimmers, in turn, simply regulate the effective voltage value.
Distinguish such dimmers by the front of operation:
1. Dimmers that cut the leading edge of the half-wave (leading edge). These are the circuits most often found in household regulators. Here is a graph of their output voltage:
2. Falling Edge Dimmers. Various sources claim that these regulators work better with both conventional and dimmable LED lamps. But they are much less common.
Conventional LED bulbs will barely change brightness with such a dimmer, plus it can hasten their failure. The effect is the same as in the rheostat circuit given in the previous section of the article.
It is worth noting that most of the cheap adjustable LED lights behave exactly the same as the regular ones, but cost more.
Adjusting the brightness of LED lamps – a rational solution
12V LED bulbs are common in sockets for spotlights, such as G4, GX57, G5.3 and others. The point is that often these lamps do not have a power circuit as such. Although some have a diode bridge and a filter capacitor at the input, but this does not affect the ability to regulate.
This means that you can regulate such bulbs with a PWM regulator.
In the same way as you adjust the brightness of the LED ribbon. The simplest version of the regulator, this one here on the wires, in stores they are usually called as: “12-24V dimmer for LED strip”.
They hold, depending on the model, about 10 amps. If you need to use in a nice shape, i.e., build in instead of a regular switch, you can find such touch-sensitive 12V dimmers on sale, or variants with a rotary knob.
Here’s an example of using such a solution:
Previously, 12-volt halogen lamps were used and powered by electronic transformers, and this was a great solution. 12 volts is a safe voltage. To power these lamps at 12 volts electronic transformer will not work, you need a power supply for LED strips. Basically, converting lighting from halogen to LED lights is all about that.
Conclusion
The most reasonable solution to control the brightness of LED lighting is to use 12V lamps or LED strips. When reducing the brightness may flicker light, for this you can try to use a different driver, and if you make a shim controller with your own hands – to increase the frequency of PWM.
| Changing the brightness of the LEDs or the controller with their own hands |
