Calculation of power consumption of 12v LED strip
LED lighting has almost completely replaced incandescent lamps. Thanks to their low power consumption and powerful luminous flux, LEDs save millions of kilowatts of energy produced on the planet. Low power consumption LED strip and its mass application has already conquered most of the world. In this article we will consider what is the power of LED strip, how to calculate it, what it affects and how to use this parameter correctly when choosing.
Definition of power
Power - a physical quantity, an indicator that characterizes the amount of energy consumed over a period of time. The unit of measurement, according to the SI (International System of Measurement) - watt, abbreviated W.
The formula for calculating power will help us:
P=I*U,
where P – power, I – circuit current, U – line voltage.
Based on the formula, in order to determine the power of the device we have to measure the current and voltage in the circuit. To measure the amperage, an ammeter is connected in series to the circuit (make a break in any wire and connect the feeler of the ammeter into it), the voltage is measured at the point of connection.
This formula helps to calculate and find out how many watts of energy the device will consume in one hour of time, and in our case it helps to determine how much power you should buy the power supply.
Example: current is 4A, voltage is 13.5V and power is 4*13.5=54W.
LED Strip
LED Strip is a flexible strip, which is based on a copper wire, across the entire area are LEDs. It is divided into modules. A module is a section of tape with three LEDs and a resistance. Thanks to this design it is possible to remove non-working section and and replace it with a new one.
LED strips have a degree of protection. It is selected depending on the place of application and environmental conditions. For example, the IP20 class is only suitable for dry rooms, as it only protects the strip from dust. The IP68 degree of protection reliably protects not only against dust but also against moisture, dripping and splashing water.
LED strips are differentiated by the size of the LEDs installed in them, their power consumption, color and light output. Later we will look at how to determine how much power and how much tape we need for adequate and high-quality lighting.
How to determine the power LED strip
A parameter that you should pay attention to in the first place. On it, as a rule, depends and the amount of light emitted. Tapes with higher power consumption have a greater luminous flux. It depends on the type of LEDs installed in modules. There are many types different LEDs. Let's look at a few of them with an example in the table.
The figure above shows how many LEDs are installed in one meter of LED strip. Each LED has an individual power consumption, if you know its type, the power can be calculated thanks to the formula and parameters from the table below.
By simple mathematical calculations can also calculate the power consumption of one meter strip for one hour of operation by multiplying the number of LEDs for their power.
Example of calculation: You have opted for a LED strip with the type of LEDs SMD3528On an area of one meter the number of elements is 60 pcs. The strip is green. From the table: current 20 mA (I), voltage 3.2 V (U). Convert milliamperes to amperes 20/1000=0.02. P=I*U, 3,2*0,2=0,096 W. The number of LEDs is 60, the power of one LED is 0.096 W, so 60*0.096=5.76 W. The power of the LED strip per meter was 5.76 W. In one coil there are 5 m LED strip, 5 * 5,76 = 28.8 watts, so the power consumption will be 28.8 watts per hour.
The manufacturer indicates the power on the packaging of products, but it is strongly recommended to check it before installing .. It may turn out that it does not match the declared. Here is a clear example of the difference in power of LED strips in the table.
Table of power consumption of different types of LED strips.
| LED Type | Diodes per 1 meter | Power, W |
| SMD 3528 | 60 | 4,8 |
| SMD 3528 | 120 | 7,2 |
| SMD 3528 | 240 | 16 |
| SMD 5050 | 30 | 7,2 |
| SMD 5050 | 60 | 14 |
| SMD 5050 | 120 | 25 |
How to choose the right power supply
The power supply of the tape is selected on the basis of the load it is connected to. To do this, the total load of all the ribbons to be connected is added up. Depending on the convenience of switching and the power of the equipment, two or more power supplies may be used in the lighting system.
For correct and stable operation of the equipment power reserve of the device should be at least 20% of the connected load. It allows you to reduce the heating of the device.
The label on any power supply tells you how much load it can handle. If the total calculated load of the circuit is 200 watts, then the power supply example given above will fully satisfy us: 200W+20%=240W. Do not exceed the load threshold - the device will heat up and fail quickly.
What power to choose the tape to light the room
We promised to tell you how to know how much light you need for the right and high-quality lighting in the room. Knowing the power of the LED strip, determine how much light we get from it, it is not difficult. In the table of characteristics, there is a parameter such as luminous flux. What does this mean?
The theory of .
Luminous flux - is a number which indicates how much light is emitted by the light flux. It is measured in lumens (Lm for short).
Illuminance is measured in lux (SI lx) which gives the ratio of the amount of light falling from one meter of height to one square meter of area.
Illuminance depends on how far away the light source is located. The farther away the lamp, the weaker it shines. In physics this phenomenon is explained by the law of inverse squares.
The law of inverse squares states that the value of a certain physical quantity at a particular point in space is inversely proportional to the square of the distance from the source that characterizes this quantity.
Calculation
Suppose that the ceiling of our room is 3 m and 20 cm high. The already compiled ceiling height coefficients will help us simplify the task of calculation:
- Height 2.5 m - 3 m = factor 1.2;
- Height of 3 m - 3.5 m = coefficient 1.5;
- Height of 3 m - 5 m = factor 2.
Table of norms of illumination of living space.
| Room type | Illuminance level, LK | Maximum value of ripple factor, % |
| Living rooms | 150 | 20 |
| Kitchen | 150 | 25 |
| Bathroom | 50 | - |
| Corridor | 50 | - |
| WC | 50 | - |
| Vestibule | 30 | - |
| Stairs | 20 | - |
The table indicates that a living room requires illumination of at least 150 lux. Calculation formula using the coefficient:
E=N*K*S,
Where N - required illumination, K - ceiling factor, S - room area.
Let's take the average size of the room 3 meters wide and 4 meters long, the ceiling height is 3.2 meters, therefore:
150 * 1,5 * 12 = 2700 Lm.
Let's calculate the luminous flux of the tape. Consider the calculation on the example of SMD5050 ribbon 60 pcs/m, color white. In the table shows the luminous flux of 11-12 lumens per LED. We take 5 meters of tape, in one meter there are 60 LEDs, in five meters there are 300. We will multiply the average value of the luminous flux 300*11,5=3450 Lm. Received value of the luminous flux of 3450 Lm.
Conclusion: 5 meters of tape will be quite enough to illuminate the living room.
Useful video: connection and calculation of power LED strip.
