RGB LED strip - types, device, schemes

In addition to white LED stripswhich were described in the previous article, tapes with color LEDs are also available. Currently, it is only 4 colors: red, blue, green and yellow. The LED housings are the same as in the white tapes. Colored ribbons are used mainly for decorative lighting, modding of computer cases and cars, as well as at discos and other entertainment events.

Tri-color LED strip

Usually they are called RGB tapes. Each LED of such a tape is an assembly of red, blue and green LEDs. RGB tape has 4 pins. One conclusion is common and three separate conclusions for each color. Connecting an RGB tape is shown in the figure. 1.

According to the laws of physics, from these colors you can get the whole gamut of shades. This is how colors appear on the TV screen. Naturally, to control such a tape, you need a control device - a controller. And such controllers are manufactured industrially.

Using the controller, you can change the speed and alternation of various colors, set some fixed hue, and the one you like can be saved in the controller’s memory and called up in the future by pressing a single button. If desired, you can get just white lighting.

More advanced models have built-in Wi-Fi, which allows you to control the lighting using a smartphone with installed software. Controlling the controller is also possible using the remote control supplied with the controller.

Picture1. RGB tape connection

RGB tapes are available at 12 and 24V. Therefore, when choosing a power supply and controller, this parameter needs to be paid special attention. The controller itself can be designed to work with several voltages, but the voltage of the power supply must strictly correspond to the voltage of the tape used.

Sealed LED Strip

Such tapes have several names: hermetic, waterproof, and even completely waterproof, although in essence it is one and the same. An example is the tape “Waterproof LED Strip 3528 120LED-24V IP65”.

As can be understood from the marking, the tape is made on the basis of SMD3528 LEDs with the number of LEDs 120 per meter. Tape supply voltage 24V, protection class IP65. The tightness of the tape is ensured by coating with a silicone shell on the part side. The appearance of the tape is shown in the figure. 2.

Picture 2. Waterproof LED strip

Such a tape can work outdoors and even in water. It can be used to illuminate aquariums or pools. All LED strips, not only waterproof ones, have a similar marking indicating the supply voltage, the number of LEDs per meter and the type of LEDs. Focusing on the marking, you can quite accurately select the desired tape when buying.

Calculation of the power of LED strip

It turns out that such a calculation is not necessary at all. Below are two lines in which all parameters are indicated. led strip 5m long. This entry is taken as it is, from the order of the LED strip in a Chinese store with free shipping. It was such a tape that the author of the article had to order to repair the monitor. 5m-48w-120x3528smd-1800-2400lm-6000-7000k-cool-white-light-led-strip-light-dc12v

From the marking, you can understand that we have a tape with 120 LEDs per meter type 3528SMD. The length of the tape segment is 5M, the light intensity is 1800-2400LM (lumen), and the supply voltage is 12V DC. The color of the glow of the tape is cold white, as indicated by the indicated color temperature of 6000-7000K.

Here, the power of a 5-meter section of the tape is indicated, no less than the whole 48W.In this case, the current consumed by such a segment will be I = P / U = 48/12 = 4 amperes. Therefore, the power supply for such a tape should be rated for a current of at least 5A. There must be some kind of power reserve! But still let me tell you about free shipping.

The issue price was more than modest, only 631 rubles. It turns out that one meter costs a little more than 120 rubles. In stores that sell all kinds of electrics, it is cheaper than 200 rubles to buy an LED strip, and besides the size of 60 LEDs per meter, they simply do not offer another. Speaking of free shipping. When ordering parts in domestic online stores, the shipping cost may exceed the cost of the purchase itself, which, of course, poisons the joy of the purchase.

The only thing that is not good in free delivery was sent only a month after the order. The appearance of the tape is shown in the figure. 3.

Picture 3. LED Strip 5m-48w-120x3528smd

But still, you can calculate the power. One meter of such a tape consumes power 48/5 = 9.6 watts. It is known that the length of three LEDs, the minimum that can be cut with scissors, consumes a current of 20 mA. With a 12V supply voltage, the power of such a segment will be P = U * I = 12 * 20 = 240mW or 0.24 watts.

With a LED frequency of 120 / m, each meter contains 120/3 = 40 triads. So far, it seems, there are no errors in simple calculations. Let's continue further.

If one triad consumes power of 0.24 watts, then the forty triads that make up each meter of tape will require 40 * 0.24 = 9.6 W from the power supply, which completely coincides with the above calculations. Here is a kind of check. Similarly, you can calculate the power of other types of LED strips.

See also on our website:

How to choose the right LED strip for the home

LED Strip Power Supplies

A suitable power supply for the above LED strip is also possible to buy in stores with free shipping. Here is one of the options.

"AC 110-240V to DC 12V 5A power converter." So it is written in the store. The price of the device is 526 rubles, in appearance it resembles the power supply of a regular laptop. The appearance of the device is shown in the figure. 4.

Picture 4. Power supply DC 12V 5a

This, of course, is not the only option. A wide variety of sources are offered, as well as RGB tape controllers. At the same time, power supplies have the most diverse design. It can be simply assembled printed circuit boards without a case, moisture-proof sources, small-sized sources that are easy to hide from prying eyes.

But in principle, you can not buy anything. Many hams, for sure, have preserved power supplies from old computers. They have a voltage of 12V, and the current can reach up to 8A. Just a ready-made solution to the problem!

Is it possible to power the LED strip from the lighting network

But if you do not want to deal with the power supply, select according to the power, hide it in the niches of the wall or in the table, then for decorative lighting, LED strips with power from the network are produced. The characteristics of one of these tapes are shown below.

9.6W 480lm 120-SMD 3528 LED Warm White Light Decoration Strip (220V / 2-Flat-Pin Plug / 2m), and the appearance of the tape is shown in the figure 5.

Picture 5. Mains led strip

Such a tape is offered at a price of 492 rubles, its length is 2 meters.

One can only guess what is in the box located between the mains plug and the tape, but it is unlikely that there is a simple quenching capacitor with a rectifier bridge: galvanic isolation from the network, it is also the user's electrical safety - first of all. With the modern development of switching power supplies, it is not difficult to hide a source of 10 ... 12 W in such a volume. So galvanic isolation is provided.

LED strips in amateur designs

One of the directions how repair of monitors and TVs has already been mentioned in the previous article. What else can be done on the basis of LED strips? If these are colored ribbons, then it is clear that various automatic lighting effects machines and various garlands can be made from these ribbons. On the basis of RGB tapes, radio amateurs create controllers that allow you to get various lighting effects, and on the basis of white tapes, various lamps are developed.

As part of the fixtures, developments are going in the direction of how to make the LED strip work directly from the lighting network. One of these schemes was developed by a radio amateur K. Moroz from the city of Belebey, Bashkortostan.

The development idea is this: the LED strip is cut into triads, which are connected in series. This connection allows you to increase the supply voltage. If only two triads are connected in a sequential manner, we get a tape with a voltage of 24V. If you increase the number of segments to a dozen, the supply voltage will jump to 120V! At 310V, this is exactly what you get after rectifying the mains voltage, you need 310/12 = 25.833, round up to 26, the triads of the LED strip.

The author of the development managed to manage with only 18 segments, connecting them according to the scheme shown in the figure 6.

Picture 6. LED strip in the table lamp

Perhaps, here someone will say: “Yeah, but where is the galvanic isolation, where is the electrical safety?” There is nothing special to object to, but where did you see the desk lamp with galvanic isolation? The main thing here is not electrical safety, but a simple and beautiful solution to the problem.

The author's article was published in the journal "Radio" No. 6, 2014 under the name "LED strip in a table lamp." The author of the article tells in detail what prompted him to engage in such development, a detailed description and photographs of the design are given.

A small remark to the scheme. The number of triads used can be changed if necessary, and the capacitance of C1 will also have to be changed, since it is it that absorbs excess network voltage. Recommendations for the calculation of a quenching capacitor are given in the article. “How to connect the LED to the lighting network”.

Boris Aladyshkin

See also on this topic:Homemade LED Strip Light