LED strip for plants: the nuances of connecting and using

Sunlight plays an important role in plant life, its lack negatively affects photosynthesis, which leads to a slowdown in vital functions. You can solve the problem using artificial lighting. But ordinary lamps are not suitable for this purpose, since a special spectrum is required, which not all light sources can emit. Consider how to make your own lighting for indoor plants or seedlings using LED phyto tape. Let's start with the theory.

LED spectrum length for plants

It has been established that for biological processes occurring in plants, a certain length of light waves is necessary. Figure 1 shows a graph demonstrating this relationship.

Designations:

• A is a graph of chlorophyll synthesis;
• B - photosynthesis;
• C - photomorphogenesis.

We see that plants absorb most intensely light waves with a length of 445 nM and 660 nM, which are in the blue and red parts of the spectrum. That is why conventional sources are not suitable for artificially lighting, you will need a phytolamp or phyto-tape. The most effective backlight, in which the ratio of blue and red light is 1 to 4-6.

Advantages of phyto tape over other sources

Here are a few factors that favor LED backlighting:

• lower consumption compared to halogen, mercury and luminescent phyto sources;
• narrow spectral range guarantees maximum efficiency;
• low voltage increases security;
• high efficiency;
• less susceptible to heating than bulbs, therefore, they can be closer to plants, which allows the use of a source of lower intensity;
• do not contain substances that pose a threat to health.

Unfortunately, such a source has one significant drawback that limits its widespread use - high cost, so we will consider alternative options.

LED strip for full-spectrum plant growth

This is sometimes called RGB sources, which is not correct, since installing full-spectrum LEDs on a tape is technologically impossible.

The USKI source is a blue-spectrum LED coated with a special luminescent layer. This design allows you to emit a luminous flux in the range of 400-800 nm, while the peak intensity falls on 630-640 nm (the spectrogram is shown in Figure 3).

Some unscrupulous manufacturers indicate in their products a peak intensity of 660 nM, to put it mildly, not true, since the technology used does not allow to obtain a source with such characteristic. This restriction can be circumvented in the manufacture of matrices, for this purpose I install several crystals of the red spectrum in them.

The cost of this type of LED source is not much less than a phyto tape, which makes it not a perfectly acceptable alternative.

Using blue and red LED strips

As an economy option, red (630nM) and blue (465nM) LED strip can be used to illuminate indoor plants. Their peak intensity is somewhat offset from the phytospectrum, but this is not critical, the effectiveness of such lighting will decrease, but only slightly.

Instead of two tapes of different colors, you can use one RGB, but to control its work, in addition to the power supply, you will need a special controller, which leads to an increase in the cost of construction.

Calculation of backlight power and tape length

To illuminate indoor plants or seedlings, the lamp power is selected at a rate of 30-50 W per square meter (in the presence of natural light). Knowing the characteristics of the LED strip and the area of ​​the room greenhouse, it is easy to make the necessary calculations.

Let's say we need to organize a backlight for a seedling box with an area of ​​0.2 m² (20х100) cm, therefore, the power of the backlight source should be 8 W (40 * 0.2). If you choose the tape 3528-60 (4.8 W / m), then it will take two meters.

Do not forget about the ratio between the red and blue LEDs, which means we take 0.5 m of blue tape and 1.5 m of red, that is 1 to 3. As a result, the backlight will have 30 blue LEDs and 90 red.

You should pay attention to the peculiarity of the tapes, it consists of segments, each has three LEDs, this is an indivisible part that determines the multiplicity of cutting. For 3528-60, this parameter is 5 cm, and for 3528-120 it is 2.5 cm. In Figure 6, a red circle marks the place where cutting can be performed.

It does not make sense to use a tape with a silicone coating to illuminate domestic plants, especially since it reduces the intensity of the light flux.

Power supply for backlight

Having decided on the power of the tape, we select a power supply for it. Here it is necessary to take into account the characteristic features of LEDs, they require stabilization by current, not voltage. Ohm's law will help to calculate the current consumed by the tape: I = U / P, where U is the supply voltage of the tape, P is its power. For example, for a luminaire consuming 9.6 W, you need a power supply (12 V) at least 0.8 A (12 / 9.6 = 0.8). The cost of such devices is about 100-120 rubles.

Given the low cost of a PSU of this class, it does not make sense to do them on your own, for "amateur radio itching" it is better to find a more worthy application.

Doing a more powerful current stabilizer with your own hands is also pointless, on the well-known site of Chinese manufacturers to purchase such a product, as shown in Figure 8, you can only 50 rubles (with free delivery).

Please note that the device shown in the figure is a current stabilizer designed for input voltage from 3.5 to 35 V (direct current), respectively, connect it directly to a wall outlet, where 220 V, not allowed. First, it is necessary to lower the voltage and convert it from alternating to direct, i.e. to assemble the simplest circuit based on a transformer, a diode bridge and a polar capacitor (see fig. 9).

Connection

Now that we have decided on everything we need, we can begin to manufacture a phyto-lamp for a box with seedlings of 20x100 cm. If you need lighting for another area, the article provides all the information necessary for recalculations.

From the materials we need:

• a fragment of a fiberboard sheet 4-6 mm thick and 60x20 cm in size;
• profile for drywall UD-27 - 2 meters;
• LED strip for plants - 2 m or 1.5 m red and 0.5 m blue;
• power supply for 12 V and 1 A;
• stranded copper wire with a cross section of 0.75, for example PVA;
• fasteners.

Tools required:

• 25 W soldering iron;
• ordinary and metal scissors;
• screwdriver with a cross bit and a drill with a diameter of 3 mm;
• mounting knife.

Build Algorithm:

1. We cut the UD profile into four equal pieces 50 cm long.
2. We install the profile on the fiberboard, so that 5 cm is left to the edges of the sheet, and there is the same distance between the profiles.
3. We cut the tape into pieces 50 cm long; during this operation, care should be taken not to cut the segment.
4. We remove the layer protecting the pecking surface from the back side, after which we attach the tape inside the profile.
5. We connect the tape to the power supply, as shown in Figure 10. It makes sense to install a terminal block on the back of the fiberboard, where to lead the wires from the tapes and PSU. Soldering must be done carefully so as not to damage the tape. Observe the polarity, improper connection will disable the LEDs.

   

1. We turn on the assembled structure and check its performance.

The assembled luminaire can be mounted on racks or suspended above plants.