Programmable LED strip. RGB LEDs: addressable LED strip. Using microcontrollers

I took the waterproof version, which is designated by the seller as “White 4m 60 IP67”, this is a tape in silicone. Came on a reel, in a foil bag:


On one meter there are 60 lights filled with silicone:


On the reverse side there is double-sided tape for attaching to the surface:


Let's look at a separate section of the tape:


We see: cutting lines along the contacts, the actual contacts on both sides: DIN - input data, DO - output data, +5V - power plus, GND - power minus, C1 - ceramic capacitor, and the LED itself is soldered with 4 contacts. The direction of data transfer is indicated by a black triangle.

The WS2812B LEDs themselves are an assembly of a microcircuit and 3 LEDs (red, blue and green), thanks to a special protocol, the microcircuit receives data only for its assembly, and transmits the rest of the data further along the chain. Thanks to this, each individual assembly can be given information about the brightness of each LED (red, blue and green) and get the desired color.

The properties of an individual assembly are described in detail. I will just note that 1024 microcircuits can be connected in maximum series, the information in which can be updated 30 times per second.

A good library for these assemblies has been developed for Arduino. Which allows you to paint each assembly in its own color. Adafruit also has a library for screens from these assemblies and good examples of use.

We have already seen on this site wonderful creative results using the WS2812B: , .

I wanted to make a controlled window tape using this tape. We will glue the tape into the window opening, so we will need 2 meters of tape. Having assembled a prototype of a simple garland and downloaded the example included with the Adafruit_NeoPixel: strandtest library, I was convinced that everything basically works. In fact, the library specifies one controller pin that is connected to the Din input of the first assembly.
Scheme:


There were no problems with the standard sketch and standard connection.

But we need to control the ruler remotely... This is where the rake begins.

First of all, I decided to connect the IR receiver and control it from the remote control. I assembled the circuit, blinked the LED and connected the tape... There was no reaction... More precisely, when I connected the console, I received random button codes, pressing one button 10 times and seeing only different codes, I thought. The first thought was that there was a problem with the power supply, because apart from turning on the tape, nothing had changed. I read on the recommendation to solder an electrolyte with a voltage of 6.3 Volts and a capacity of at least 1000 μF to the input of the tape, of course I did it right away, the result was zero... I started digging the code of the Adafruit_NeoPixel library and discovered that when transmitting data to LEDs, the library completely blocks interruptions. Disabling the blocking resulted in the tape behaving very strangely; interruptions occurred due to any debris that entered the IR receiver input...

Frustrated by the failure of such a simple scheme, I began to think about a second controller, responsible for receiving IR signals and controlling the main one... If someone wants to make an IR-controlled tape on the WS2812B, then this is the only reasonable option. Of course, there are also exotic ones, for example, introducing time intervals when the garland does not change its state and receiving IR signals in them - but this is a completely horny method...

As a result, I decided to use bluetooth and control the garland from my phone, since I had several HC-06 modules lying around idle. To indicate the current operating mode of the garland, I decided to use the display on the TM1637, a review of which is available. Final scheme:

The main problem that arose with the code is that when changing state, delay() is used, which does not make it possible to intervene in the process except with interrupts, but... we have interruptions disabled... It was decided to rewrite the effects using storage of information about the current state of the garland and changing it according to timing. For this purpose, cycles are transformed into transitions to the next state, and signs of mode changes are added. I had to think about whether it was worth posting the crooked experimental code, but the desire to make his creative process easier for someone overpowered - (the code there is absolutely experimental, use at your own peril and risk).

Now about the controls, of course, writing your own beautiful application is a tempting idea, but there was no time for that, so I used the android application, set up the necessary codes in button mode and everything was fine. It is possible to sign the sent code and designation for each button. I didn't need more. I numbered all the effects so there are 10 different ones, 10 buttons are used for effects, and 1 button is for turning on the sequential change of effects.

The Bluetooth module was configured using the program, very convenient, you can change the name of the device when searching and the speed:


The HC-06 should be connected to a computer using a standard USB-TTL converter.

Having connected it to a laboratory power supply, I found out that my tape (2 meters) consumes 2.1 A at a peak voltage of 5V when everything is turned on. I installed a 3A power supply purchased offline:


A week of continuous operation revealed no problems.

And of course, I wanted the finished device not to look like a tangle of wires in a shoebox. Moreover, I had cases with a glass lid of a suitable size:


We make a printed circuit board in the Sprint Layout program, I still left the IR receiver, since another use of the box is possible, or somehow we can solve the problem with it:


I described the manufacturing process using the LUT method earlier in.
This is what the board looked like with toner applied:


Etching:


Assembling the device:


To connect the garland, I used a headphone jack, which also supplies power to the device. The wire to connect the power supply to the tape I used PVA 2x0.5, and to connect the device to the tape I used a 4-core telephone cable, I made the ground from 2 wires.
Final device:






Well, its effects:










Of course, it’s best to watch the garland on video:

Today, it is unlikely that anyone can be surprised simply by a luminous sign or a bright light box with a painted picture. The consumer demands spectacle, and the static advertising image is rapidly becoming a thing of the past, giving way to dynamic displays and signs with running lights, iridescent letters, in general - static is being replaced by dynamics.

And this is not at all surprising, because programmable LED controllers, allowing you to easily create unique dynamic lighting effects, which, in combination with modern LEDs, can create real visualization miracles.

A small controller box for a sign, at the request of the designer, will enliven an LED line, a composition of, or a large LED cluster - a block of individual LEDs or a block of entire lines of LEDs. Such solutions based on the corresponding programmable multi-channel controllers allow designers to implement the most intricate ideas for signage.

Pairing multiple controllers will make the sign even more vibrant, not to mention the thousands of available shades and dozens of brightness gradations. In this case, to create effects, the user just needs to open a program on the computer, write a light script for the sign, connect the controller to a USB port, write the finished program into it, and that’s it - the controller can be connected to the sign. By the way, some controllers can be equipped with light sensors and remote controls.

Programmable controllers are, in principle, capable of controlling both conventional monochromatic clusters and RGB clusters at voltages usually up to 24 volts, although everything depends on the controller model, its complexity, and the designer's goal.

The controller is able to provide up to 262,000 color shades at user-specified brightness, and each channel of the controller will work individually. In principle, the number of channels is not limited; it is enough to dock and synchronize the required number of controllers with each other.

By creating a script in the program, the user will be able to immediately test it visually - figure out what the sign will look like, and immediately make adjustments at their discretion. In short, the system is quite flexible. And if previously the developer had to design complex analog circuits, now it is enough to write a program in a friendly and very visual environment.

iMLed16x3_Pro (16ch,2A/ch) from Impuls Light

The controller size is 20 by 10 cm, and 3.5 cm high, with a weight of only 200 grams. The controller is capable of controlling up to 16 channels, at voltages from 5 to 25 volts, and the maximum current of 32 amperes, for 16 channels of 2 amperes, is achieved with a 12 volt LED supply.

The program is loaded via a USB cable using the supplied proprietary DynamicLight application, with which the user has the opportunity to write programs in 1336 steps for one controller with a time step size from 5 milliseconds to 4 minutes.

The speed of script execution is entirely adjustable at the user's request. Thus, the user gets the opportunity to create a dynamic scenario of any complexity in a matter of minutes.

The user has 16 channels or 5 independent groups for RGB at his disposal. You can connect monochrome modules and strips, pixel LEDs and RGB clusters for voltages from 5 to 24 volts.

The "DinamicLight" program for flashing a script into the controller is presented as a matrix, which the user needs to fill out by assigning a shade, on and off mode for each component or group, enable effects (overflow, transition, stroboscopic effect, etc.) and also set the time between transitions. The hue is set manually from the palette, and the brightness and time are set simply by entering numbers.

The convenience of using the program also lies in the fact that each group of LEDs can be named by its own name, so as not to get confused in the process of creating the script.

To create more channels for a sign, or supply more current to the elements, it is enough to synchronize several iMLed16x3_Pro controllers with each other using the master-slave principle, and then connect the controllers to each other with a two-wire cable.

Dominator 810 from RUNLINE

The controller measures 11.5 by 6.5 cm, and 4 cm in height, with a light weight of 330 grams. The controller is capable of driving up to 8 channels, with voltages ranging from 4 to 25 volts, with a maximum total current of 40 amps and a maximum current per channel of 10 amps.

The program is loaded via USB using the included proprietary Led controller software, with which the user has the opportunity to write programs in 65,000 steps for one controller with repetitions, and with a frame duration from 1.6 milliseconds to 4 seconds. You can create a dynamic scenario of any complexity using the application in a matter of minutes.

There are 8 channels available for programming. You can connect monochrome modules, strips, pixel LEDs and displays for voltages from 4 to 25 volts.

The window of the "Led controller" program for flashing the script is presented in the form of a matrix of cells with rulers: the channel name in the vertical and the operating time in the horizontal, which the user fills in by assigning the on and off mode of each component or group, adding effects, setting up operating time intervals using a convenient slider.

The ease of use of the program lies not only in the visual presentation of the sign, but also in the ability to name each channel to make it easier to navigate when building a script.

To create more channels for a sign, it is enough to synchronize several Dominator 810 controllers with each other, and you can write a program for several controllers at the same time, there will simply be more channels in the window, and the cells for each controller will be colored in their own color.

Andrey Povny

Smooth increase and decrease in current level, the ability to work with LEDs from different manufacturers and with different binning, time-based dimming programming without laying a separate control bus, ensuring a stable luminous flux as the LEDs' lifespan wears out, a high degree of protection IP67 - all these are features programmable LED drivers production companies MEAN WELL And Inventronics.

When developing an LED lamp, an engineer has to solve a number of problems related to ensuring the required lighting performance, electromagnetic compatibility, and thermal conditions. At the same time, it is important not to forget about the availability of the selected components on the electronic components market. In addition, economic and technological aspects should be taken into account. When solving these problems, the developer must determine the manufacturer and type of LED, as well as the manufacturer and type of secondary optics, and calculate the required number of LEDs. When calculating the number of LEDs, it is necessary to adapt to a certain “standard” current value of power supplies available on the market. When choosing LEDs, you should take into account binning and its range, additional losses that arise in the secondary optics and when the LED module heats up. The connection circuit of the resulting array of LEDs must be such that a given current flows through the LEDs, and this current would correspond to the current of the power supply available or intended for use. It turns out that the developer, and subsequently the manufacturer, is tied to the selected components and their availability in suppliers' warehouses at the right time. And one of the main components on whose parameters this choice is based is the power supply or LED driver.

The market situation changes quickly, and sometimes unexpectedly. What was profitable yesterday may not be profitable today. In Russian realities, it is often necessary to manufacture products in emergency mode, and the supplier may not have the required components. On the other hand, there is always a wide selection of components on the market from both famous and not very well-known manufacturers, and their products may be in stock at a given time. Manufacturers are constantly changing product lines, improving parameters and/or reducing costs. Some LED manufacturers even have standardized housing sizes, for example, 3535 (the type produced by the company Cree and similar ones). We have already come to the conclusion that LEDs and even secondary optics from different manufacturers can be used on a specific printed circuit board without redesigning it. Of course, changing the type or manufacturer of the LED will lead to some lighting technical changes (components from different manufacturers have different binning and efficiency), but these changes could be compensated for by changing the power supply current. However, if an unregulated power supply has been selected, this becomes impossible. Changing the existing power supply will require new certification tests for the luminaire. In addition, there is no guarantee that these tests will be met.

It often turns out that the output current of the power supply needs to be changed quite a bit, literally within 10...20%. In this case, it is impossible to replace the unit, because the output current step, even within one series, is significantly larger and has a standard value, and we need some intermediate value.

So, the power supply selected earlier at the development stage may in the future turn out to be a limiting element and will not allow, if necessary, to replace some individual components of the lamp or its parameters.

We know that there are power supplies with adjustable capabilities that could be selected at the design stage. There are three options for such blocks, but how convenient are they?

The most common power supplies are adjusted by an internal potentiometer. However, when using them, the complexity of assembling the lamp increases, since adjustment is required using a measuring device. In addition, such power supplies fundamentally cannot have a degree of protection from external influences higher than IP65 (due to access to the potentiometer).

Power supplies with current changes via DIP switches have a discrete adjustment step, which may not suit the designer. Again, due to the presence of such switches and the need to access them, such units are only suitable for indoor use and are not suitable for outdoor lighting.

The third type of power supply with adjustment includes power supplies with a “3-in-1” dimming function (PWM, 0...10 V, resistance). By connecting a constant resistor to the control input, you can reduce the output current to the value we need (at the same time the output power will also decrease). In this case, a degree of protection of IP67 is possible. Overall this is a good option. However, not all power supplies have this possibility of dimming with resistance. Also, the dimming function means an increase in the cost of the product, and the use of this function will be quite limited.

Thus, among the available methods for adjusting the output parameters of a power supply, there is no ideal option.

Currently, another class of power supplies has appeared on the LED driver market - programmable ones, which, along with the ability to change the output current, provide a whole range of additional properties and useful functions, and also lack some of the disadvantages mentioned above.

Programmable drivers are available in the product line of companies such as MEAN WELL(family) and Inventronics(families , EBD) (picture 1). The use of the specified class of drivers in luminaires allows the following functions to be performed:

• change in output current in the range of 10...100% without reducing the degree of protection from external influences. The degree of protection remains at IP67;
• smooth increase in current through the LEDs when the lamp is turned on. This has a beneficial effect on the reliability of the LED module, especially in winter;
• possibility of smooth increase/decrease between programmed current levels (smooth change in illumination);
• compensation for “aging” of LEDs. It is possible to produce a lamp with a constant luminous flux throughout its entire service life;
• forced switching on at the right time of the lamp operating in time-dimming mode to maximum brightness (MEAN WELL only);
• alarm about the exhaustion of the lamp's life (MEAN WELL only);
• programming the required parameters of external temperature protection of the LED module or the lamp as a whole, upon reaching which the output current will decrease (Inventronics only);
• user programming of various fixed and adaptive dimming profiles over time (up to 5 current levels): proportional mode and midpoint mode.

Let's take a closer look at some of the above functions.

LED aging compensation

LEDs are very durable (50...100 thousand hours). It is generally accepted that the end of service life is a decrease in luminous flux by 30%. During operation, the luminous flux of the lamp slowly decreases. This fact can be initially taken into account when programming the LED driver and set the initial current through the LEDs lower, for example, by 20%, but increasing by the end of the service life to 100% (Figure 2). Of course, one should take into account the increase in power consumption of the lamp towards the end of its service life.

Rice. 2. Screenshot of the software interface from Inventronics and MEAN WELL in LED aging compensation mode

Dimming by time

The dimming function is very popular in lighting. It is especially interesting in outdoor lighting, as it allows for optimal energy consumption. Moreover, the current GOST R 55706-2013 “External utilitarian lighting. Classification and Standards" allows for a decrease in illumination at night (up to 30% and up to 50%) on streets, squares and local areas, depending on the intensity of traffic.

Implementing the ability to dim outdoor lighting requires significant costs. Only dimmable power supplies must be used in luminaires, and, at a minimum, a control line for these luminaires must be installed. Using programmable power supplies, dimming can be implemented without installing an additional control line or an additional controller, which will significantly reduce the overall cost of the lighting system. Such power supplies allow you to program different output current values ​​depending on the start of the lamp operation time (Figure 3).

When we consider time dimming (fixed and adaptive modes), it is important to understand that the lamp itself does not turn on or off. Switching on and off is carried out by the operator in manual mode or by a sensor signal in automatic mode. The dimming program always runs from the very beginning and every time it is turned on.

From Figure 3 it can be seen that the dimming profile of LED drivers manufactured by Inventronics can be programmed for a period of up to 19 hours (at MEAN WELL in fixed profile mode - up to 24 hours). However, this does not mean that after 19 hours of operation the lamp will turn off. The lamp cannot turn off on its own. It’s just in this interval that you can change the output current. After 19 hours of operation and until forced shutdown, the power supply will continue to operate in the same mode in which it was operating before the end of the programming period. If we do not take into account the realities of the north, where night and day last for six months, then for the rest of Russia this period of time (19 hours) is quite enough. If not, then you can organize a short-term switching off/on of the lamp using an external timer so that the daily countdown starts again.

The presence of a time dimming function from Inventronics and MEAN WELL are called “Timed dimming” and “Smart Timer Dimming”, respectively. In terms of functionality and capabilities in terms of fixed and adaptive dimming, they are very similar to each other and work according to a similar algorithm, but there are some differences in general capabilities.

Fixed dimming means that the power source always operates strictly according to the programmed profile. This would be good if it were not for seasonal changes in light. For example, if we program the first reduction in illumination 4 hours after the start of operation, which corresponds to approximately 01:00 in the summer (provided that switching on occurs at 22:00), then in winter this will correspond to 21:00 (switching on at 17:00), and at this time there is heavy traffic on the streets. Due to seasonal changes in illumination, a fixed dimming mode in outdoor lighting is almost impossible to use.

A more interesting option that can be practically implemented is the use of adaptive dimming, that is, one that adapts to seasonal changes in illumination.

Both manufacturers under consideration have two adaptive dimming modes in their programmable power supplies: the proportional principle and midpoint self-adjustment. When programming the power supply, the program interface allows you to choose between any dimming options.

Adaptive dimming: proportionality principle

The principle of proportionality ensures a proportional change in each section of the programmed profile in accordance with the increase or decrease in the total operating time of the luminaire. Let's assume that we have programmed the power supply to operate in the autumn-winter period according to the profile shown in Figure 4a. The total operating time is 15 hours a day. Here and further in the text, the profile type is chosen conditionally.

Rice. 4. Power supply profile: a) programmed for the autumn-winter period; b) rebuilt for the summer

As we approach summer, the total operating time of the lamp decreases. For example, turning on and off occurs using a light sensor. The power supply microcontroller analyzes the operating time and determines that the time the source is in the on state has decreased. Then, the next time you turn it on (the next day), the programmed profile is rebuilt in proportion to the change in the operating time of the source.

Let’s say that in the summer it turns out that the power source no longer works for 15 hours, but only 9. Then its profile will be rebuilt and will have the time intervals shown in Figure 4b. The figure shows that the duration of each interval decreased in proportion to the reduction in total time with a proportionality coefficient of 9/15.

During programming, we chose that the first reduction in current should occur at 00:00 hours, and after the restructuring it will occur at 00 hours 35 minutes. An inaccuracy of 35 minutes is quite acceptable, since we considered the edge cases (summer-winter).

To understand the algorithm for restructuring the profile in power supplies manufactured by MEAN WELL, you can refer to Figure 5.

The base reference period is seven working days, with the longest and shortest working periods being ignored. For the remaining five days, the average operating time is calculated, and if this average time differs from the previous result by more than 15 minutes, the power supply adjusts its profile in proportion to the change that has occurred.

Adaptive dimming: self-adjusting at midpoint

A fairly accurate result of restructuring the power supply profile can be achieved in the midpoint adjustment mode. You can select midnight (00:00) as the midpoint. Let's say we chose the dimming profile shown in Figure 6a in winter. The total operating time is 16 hours per day (8 + 8 hours relative to the midpoint). The first current reduction will be at 23:00, and the second at midnight (00:00). Let the total operating time of the source be 8 hours in the summer, then the power source will rebuild its profile relative to the selected point (midnight) so that this point remains in the middle of its operating cycle (4 + 4 hours). In this case, we see that we have retained the time of the first current decrease (23:00) and the time of the second current decrease (00:00). The result was that the power supply simply “cut” the time at the beginning and end of its cycle in accordance with changes in seasonal light.

We find that this algorithm is the most convenient, best supports the programmed profile depending on seasonal changes in illumination, and can be used for dimming outdoor lighting.

Programmable LED Drivers

MEAN WELL has introduced programming functionality into its popular family of power supplies (Figure 1). Programmable models have the suffix D2 at the end of their name, for example (100 W, 700 mA, programmable). The product line includes both series with current stabilization (CC) and series with dual stabilization mode (CV + CC) in the power range of 75…240 W. The main parameters of the ELG family are shown in Table 1.

Table 1. Basic parameters of programmable power supplies

A special feature of the family under consideration is its low cost, comparable to the cost of products from Russian manufacturers, and a long warranty period of 5 years. It should be taken into account that Russian manufacturers do not yet have programmable drivers in their product line, and when we talk about cost, we mean comparing models without a programming function. The programming function implies an increase in cost compared to non-programmable models by approximately 15...20%, depending on the output power of the source.

When programming, you can change the output current in the range of 10...100%. As the output current decreases, the output power will also decrease. It is known that with a decrease in power, the value of the power correction factor and efficiency deteriorate. In the family under consideration, when the output power is reduced by 50%, the power correction coefficient remains at 0.95, which is an excellent indicator. The real deterioration in this ratio was seen when the output power was reduced to 30% of the nominal value, in other words, if a 100 W source was operated at a load of 30 W. Therefore, when operating this family, you should expect to use it in the output power range of 100...50%. In this range of output power changes, the efficiency varies within 2...3%, for example, from 91% it will drop to 89%.

The Inventronics line of programmable LED drivers consists of three families (Table 1). They differ in technical capabilities and cost. For example, the EUD family has the widest range of series in the power range of 75...600 W and full programming functionality. Full functionality means that in addition to the ability to change the output current and a fixed dimming profile, adaptive dimming capabilities, compensation for LED aging, and programming of external temperature protection are added. The EUD family of power supplies has maximum programming/dimming functionality. It is represented by the largest number of models in the power range of 75…600 W.

In this article we will talk about color LEDs, the difference between a simple RGB LED and an addressable one, and add information about the areas of application, how they work, how control is carried out with schematic pictures of connecting LEDs.

1. Introduction to LEDs

LEDs are an electronic component capable of emitting light. Today they are widely used in various electronic equipment: flashlights, computers, household appliances, cars, phones, etc. Many microcontroller projects use LEDs in one way or another.

They have two main purposes:

Demonstration of equipment operation or notification of any event;
use for decorative purposes (lighting and visualization).

Inside, the LED consists of red (red), green (green) and blue (blue) crystals assembled in one housing. Hence the name - RGB (Fig. 1).

2. Using microcontrollers

With it you can get many different shades of light. The RGB LED is controlled using a microcontroller (MK), for example, Arduino (Fig. 2).

Of course, you can get by with a simple 5-volt power supply, 100-200 Ohm resistors to limit the current and three switches, but then you will have to control the glow and color manually. In this case, it will not be possible to achieve the desired shade of light (Fig. 3-4).

The problem arises when you need to connect hundreds of colored LEDs to the microcontroller. The number of pins on the controller is limited, and each LED needs power from four pins, three of which are responsible for color, and the fourth pin is common: depending on the type of LED, it can be an anode or cathode.

3. Controller for RGB control

To unload the MK terminals, special controllers WS2801 (5 volts) or WS2812B (12 volts) are used (Fig. 5).

With the use of a separate controller, there is no need to occupy several MK outputs; you can limit yourself to only one signal output. The MK sends a signal to the “Data” input of the WS2801 LED control controller.

This signal contains 24-bit information about color brightness (3 channels of 8 bits for each color), as well as information for the internal shift register. It is the shift register that allows you to determine which LED the information is addressed to. In this way, you can connect several LEDs in series, while still using one pin of the microcontroller (Fig. 6).

4. Addressable LED

This is an RGB LED, only with an integrated WS2801 controller directly on the chip. The LED housing is made in the form of an SMD component for surface mounting. This approach allows you to place the LEDs as close to each other as possible, making the glow more detailed (Fig. 7).

In online stores you can find addressable LED strips, where up to 144 pieces fit in one meter (Fig. 8).

It is worth considering that one LED consumes only 60-70 mA at full brightness; when connecting a strip, for example, with 90 LEDs, you will need a powerful power supply with a current of at least 5 amperes. Under no circumstances power the LED strip through the controller, otherwise it will overheat and burn out from the load. Use external power supplies (Fig. 9).

5. Lack of Addressable LEDs

The addressable LED strip cannot operate at too low temperatures: at -15 the controller begins to malfunction; in severe frosts there is a high risk of its failure.

The second drawback is that if one LED fails, all the others along the chain will also refuse to work: the internal shift register will not be able to transmit information further.

6. Application of addressable LED strips

Addressable LED strips can be used for decorative lighting of cars, aquariums, photo frames and paintings, in room design, as New Year's decorations, etc.

An interesting solution is obtained if an LED strip is used as an Ambilight backlight for a computer monitor (Fig. 10-11).

If you use Arduino-based microcontrollers, you will need the FastLed library to simplify working with LED strip ().