Sources for Tapes of LEDs (ART3342)

The tapes of LEDs or Led strips are increasingly popular both in lighting as in decoration. Available with white LEDs or in color and even with circuits that produce effects, they consist of a compelling solution and extremely simple to use. However, require care in installation and choose the right font. See in this article some tips on how to work with these strips of LEDs.

The LEDs are increasingly replace conventional bulb both bulbs (which are already a thing of the past) such as fluorescent lighting and both as decoration.

With a higher yield, smaller size and durability, they are available in formats that are not possible with conventional bulb.

Today, the tapes of LEDs with self adhesive capabilities can be achieved in rolls and used in any length.

However, it is not enough to have a tape and just plug in a power supply for the LEDs work properly. Need to know how to do it and especially do the correct choice of source as the amount of LEDs that must be fed.

The Mouser Electronics (www.mouser.com) distributes the products of one of the largest manufacturers of sources for LEDs, Meanwell (www..meanwell.com).

The sources of the Meanwell are specifically designed to feed led ribbons in a wide range of chains that depend on precisely the type of LED powered, the length of the Strip and the type of control that eventually desired.

Working with LEDs on tapes

The LEDs that are acquired in the form of tapes normally are available in rolls of 5 metres with a plug that allows your connection to a power source, as shown in Figure 3.

The recommended power supply for these strips of LEDs is 12 V, but in normal applications you can get a smooth operation in a range of 9 to 12 V voltages, which means that the source does not need to be stabilized in a simpler application. We can also find sources with higher voltages, recommended for applications where a very large amount of LEDs must be fed.

There are still cases where the tapes are specified to operate with 5 V which facilitates control through Member circuits. Check at the time of purchase to feed with the correct voltage.

The current specified for this particular roll the power supply that can go from 300 mA to more than 3, as the amount of LEDs.

Normally, when you get a roll of 5 meters, one can also acquire the appropriate font for this amount of LEDs without problems, but there are cases where we use less LEDs.

In this case, we need to know what is the current of each module to properly size our source that need not have the total current of the LEDs around the roll.

Watching a tape of LEDs, as the photo, we see that she has cut marks. These brands determine how we can use smaller tape lengths with less LEDs. The tape must be cut out in these points if we use less LEDs. To another point, we make unusable the LEDs in the industry.

See also that, to make the cut we expose the connection contacts so that they can be connected to a source.

For example, if each sector of our tape needs a current of 50 mA (typical values of the sectors are between 15 and 60 mA, depending on the type), and we’re going to feed 10 sectors (of 50 cm and 1 m, as the tape), we know that the source must provide 12 V x 500 mA.

If you look at the tapes, we will see that in every sector we have number of LEDs which have a resistor calculated to obtain the desired current.

In a tape in which we have white LEDs, for example, RGB LEDs (red, green and blue) need different currents, so that we have 3 resistors of different values in a connection as shown in Figure 6.

Each block contains RGB LEDs and then 3 resistors so that to be 12 V voltage applied the current in each is such that the combination of lights produce white.

In tapes that we can control the color, rather than a single track for the three LEDs we have 3 tracks that can be turned on separately to a circuit of effects, for example.

So, we must separate the simple sources with only two output wires, sources with more outputs that can be controlled (DIM), as shown in Figure 7.

In the models (Dimmable) control signal PWM 0 to 10 V or another track causes the brightness of the LED is controlled. Some allow control via potentiometer.

If we’re going to work with different lengths of segments you need to also have cables with connectors that are adapted to cut ribbons.

These connectors can be purchased in the same location in which they managed to buy the tapes. The connector should be according to the type of tape, that is, if there’s a power track (a color or white LEDs), or three trails to RGB, or color and thus be able to make the connection to the control circuit.

For the three color tape, connecting the source itself can be made as shown in Figure 8.

Of course a connection through the appropriate connector is much better, as shown in Figure 9.

Some companies sell the set of LEDs with a circuit of automatic effects. Typically this circuit is dimensioned to control length of tape of LEDs, which must be checked in the user manual.

If you want, however, you can create your effect from your Arduino, making the connections as shown in Figure 10 and creating the appropriate program.

See that we can’t use the outputs directly from Arduino, because the current is insufficient for a good amount of LEDs. We need the transistors that can be the BD135 for currents of up to 500 mA and the TIP31 for currents of up to 2 A, not forgetting the heat sinks and separate source with common, as shown in Figure 10.

The Meanwell boasts a large variety of sources which are characterized by small dimensions that an application requires decor, because normally should be embedded, for your time, resistance to the external applications and by income, as a source of this type must be economical.

In Figure 11 we have the typical block diagram of a font of type key Meanwell.

If we feed a lot of tapes, should be connected in parallel, each sources feeding the proper amount of LEDs, as shown in Figure 12.

Note that it is very easy to work with tapes of LEDs using the appropriate resources.

-Select the correct font for the amount of LEDs that will feed. If a source is not enough, even the current largest capacity, use more than one.

-Cut the ribbons on appropriate sizes using as reference marks.

-Make the connection with the appropriate connectors or soldering wires directly from the source tapes. Be careful in this operation not to damage the tapes

-Use correct effects circuits, with a current capacity according to the amount of controlled LEDs.

Use microcontrollers be aware of the possible differences that may be between the supply voltages of the circuit.

-Install the font in ventilated location.

The links below you can get information about installation (in Portuguese) on own Meanwell and how to buy fonts on Mouser.

We will soon be putting in some simple projects interesting site for effects on tapes of LEDs.