Calculation of the power supply for the LED strip

LED strips can work in the most difficult conditions, regardless of the weather - the products are durable and moisture resistant. For example, they can illuminate a street or a building facade. And for a long work, you need a competent calculation of the power supply for the LED strip.

To connect an LED strip, you need a power supply or driver. These are different devices.

• The driver supplies a stabilized current. For example, 300 mA. And if you connect too short a tape, the voltage will become more than the nominal, and the diodes will burn out. And if too long, then they will shine dimly. Therefore, only the lighting equipment for which this adapter is designed is connected through the driver. Reference: Drivers are used in finished products such as light bulbs and garlands.

• Power Supply. It is voltage regulated. This means that we will get exactly 12 V at the output, regardless of the power consumption. Power supplies are versatile and easier to pick up than drivers. There are a few things to consider.

The unit of measurement is W / m. It depends on 2 values.

• LED type. The dimmest tapes are used for decorative purposes and are equipped with 3528 diodes. They can be used to highlight the contours of objects. And for bright lighting, diodes of types 5050 (the most common) and 2535 are needed.
• Number of LEDs per meter of tape - 30, 60 or 120.

The power supply heats up during operation and needs to be cooled. This is done in several ways.

• Active cooling models are equipped with a cooler, which drives the air flow inside the case. Their advantages are high power and smaller dimensions, and their disadvantages are that the cooler is noisy and wears out over time. Such a system is needed when a tape of 800 W or more is connected.
• Passively cooled adapters are more commonly used in domestic environments. They are quiet, but take up a little more space. And it is necessary to arrange it so that there is an influx of fresh air. But they are more reliable, since there are no moving parts. And better protected from the elements.

Power adapters differ in the degree of protection.

• Open. The simplest and cheapest models, but also the most "gentle". They are used only in room conditions, where there is no dust and low humidity.
• Semi-hermetic. Protected from the light whims of nature. Coarse dust and water splashes are not scary for them, but constant humidity will quickly "kill" the adapter. On the street they need to be hidden under a canopy, or better in a mounting box. Protection degree - IP54.
• Sealed. Dust and moisture are kept out of the protected case. They are suitable for both street lighting and wet environments such as bathrooms and swimming pools. Degree of protection - IP65 or IP68 (* 6 - full protection against dust, * 5 - protection against water jets, * 8 - the device will withstand immersion in water).

To better understand the degrees of protection, use the table. By the way, it is suitable for all electronics.

The internals of all these adapters are the same. The output voltage for powering the tape is 24 Volts, 12 V or 5 V. The diode strip operates on direct current, and therefore it cannot be connected to the network indirectly. Although some do it by mistake. Consequences - the tape burns out and a fire can break out.

First, determine the power of the connected tape. And if there are several of them, then the load is summed up. To make it easier to navigate, use the table.

Then proceed to the calculation. It must be done in this sequence.

• Let's say you have a Venom SMD 5050 60 LEDs / M 14.4W tape with a length of 4 m. Then its total power will be: (14.4 W / m) * (4 m) = 57.6 W.
• Choose a safety factor. It is needed for the adapter to work without overloading. If the unit is used outdoors and is well ventilated, then 20% will be sufficient. And when it is located in a junction box, and, moreover, in a hot room, the coefficient should be at least 40%. Let's take into account the normal operating conditions, in which K = 30%. Then the power of the power supply should be:

57.6 W * 1.3 = 74.88 W.

• Next, you need to round this figure up to the standard value - 80 V. Our table will help you choose the desired power value.
• Sometimes the characteristics indicate not the power, but the highest output current (in Amperes). Then the power of the power supply should be divided by the operating voltage of the tape:

74.88W / 12V = 6.24A.

This means that the adapter must provide a current of at least 6.5 Amperes at the output.

As a bonus, you can calculate the consumption of electricity. To do this, multiply the power of the consumer by the time of its operation.

Let's say our feed has been running for a month, 2 hours every day. Then the consumption will be:

57.6 W * 2 h * 30 days = 3.5 kW * h.

57.6 W is the actual consumption of the lighting fixture.

Reference: a 100 W incandescent lamp will consume twice as much current during the same time (6 kW * h).

After connecting, make sure the power supply is working properly.

• Most importantly, the case should not heat up. To check this, after half an hour or an hour of continuous operation, touch it with your hand. Metal parts are desirable. If the hand can easily withstand heat, then the adapter is correctly selected.
• Listen to the work. Whistling and crackling sounds are not allowed. At the block, the cooler can only make noise and the transformer hums slightly.

When you need to use a strip of LEDs with a length of 10 or more meters, then the 5 m lengths are connected to different pins of the power supply according to the scheme.

This solution has a drawback - large DC losses in the wires. Diodes that are far from the power adapter will be dim. By the way, in order to avoid such losses for the transmission of current over long distances, alternating current with a high voltage is used. Therefore, it is better to use multiple power supplies. They are connected according to the following scheme.

It is advisable to place the adapters evenly along the entire tape, and not to collect in one mounting box. Then they will not overheat.

The calculation methodology does not differ from that used for one block.

• For example, you need to light a room 3x6 meters. The perimeter will be 18 m. For lighting, SMD 3528 60 LEDs / M tape is used, which has a brightness of 360 lm / m. n. Its power is equal to:

(6.6 W / m) * (18 m) = 118.8 W.

• Add a power factor of 25%. At the output we have:

118.8 W * 1.25 = 148.5 W.

It turns out that the total power of one power adapter should be 150 W.

The maximum length of a standard LED strip is 5 m. For illumination, you will need 3 segments of 5 m and 1 segment of 3 m long. These 4 segments will require 2 power supplies.

The first one will have the power:

(5 m + 5 m) * (6.6 W / m) * 1.25 = 82.5 W. Choosing a 100 W adapter.

Other power:

(5 m + 3 m) * (6.6 W / m) * 1.25 = 66 W. An 80 W unit will do.

Calculation of the power supply for the LED strip in the video below.