The power of visible light radiation, which is estimated by the sensation of the human eye and is measured in lumens, is the light flux. This is the energy that any source of light gives.
Wavelength
The light source transmits energy through emitted electromagnetic waves. The luminous flux is their speed, which gives information about the luminous intensity of a particular source. The human eye perceives the energy of light waves in different ways. The wavelength of 0.55 microns in green is perceived much stronger than in red with a length of 0.63 microns. In the range of ultraviolet and infrared radiation, our eyes are powerless.
That is why the wavelength is so important for characterizing the luminous flux. Given the susceptibility to the eyes, summing the wavelengths, we get a normalized value. The luminous flux is the norm of the power of that radiant energy, which is estimated due to the light sensation. Choosing a source of light energy for himself, a person complies with his equivalent power. For example, if you need to replace incandescent lamps with LED. In this case, you need to recalculate the power of the light flux.
How to do it
Luminous flux is the main indicator on this path. With the previous twenty-volt incandescent lamp, it was 250 lm. Exactly the same luminous flux of LED lamps can be provided with two to three watts, and fluorescent - five to seven. So, the benefits of LED lamps are more than obvious.
Suppose we need light sources with a power of 400 lm. An incandescent lamp should be forty-watt, a fluorescent lamp can have from ten to thirteen watts, and an LED - just four or five. Or, for example, we need a powerful luminous flux of lamps - 2500 lm. In this case, the incandescent lamp cannot be less than two hundred watt, the fluorescent one is only sixty to eighty watts, and the LED even less - only twenty five or thirty.
What are the lamps
The power consumption of any lamp is measured in watts (W). In everyday life, for example, LED lamps from one to ten watts are used, and for outdoor lighting they need much more powerful ones - there are also more than one hundred watts. But you need to know that the lamp power characterizes only the rate of energy consumption, it does not meet the concept of light intensity.
Here, only one unit of the light flux can characterize a particular source, which is a completely different parameter. It is measured not in watts, but in lumens. Not even every lamp manufacturer has these parameters correctly indicated. For example, the label on the package: a luminous flux of 280 lm for a four-watt LED lamp, which is equivalent to a fifty-watt incandescent lamp. We look at the table: the last luminous flux is not 280 at all, but all 560 lm should be. How so?
Calculations
The luminous flux unit is equal to the flux that emits a completely black body with an area of 0.5305 mm 2 at a very high temperature - 1773 ° C, when it solidifies platinum, for example. The light intensity is the density of the light flux in the spatial sense, it is important to consider how the light flux correlates with the value of the solid angle (and the solid angle is the part of space where all the rays converge). So: the unit of luminous intensity is not lumen, but candela.
What is illumination? This can be called the surface density of the light flux, which falls on the surface, equal to the ratio of the light flux itself to the size of the illuminated surface, where it is evenly distributed. Illumination also has its own unit of measurement, and this again is not lumen. And not even candela. This is a lux (lx). What will be one lux if the luminous flux is equal to one lumen, distributed uniformly over the area of one square meter? And here: 1 Lx = 1 Lm / 1m 2 .
Brightness and luminosity
Luminous fluxes can be of different brightness and luminosity (luminosity). Brightness is the equality of the surface density of light intensity and its ratio to the area projected by the luminous surface onto a plane perpendicular to this direction. The unit of brightness is considered to be one candela per square meter (1 cd / m2).
Luminosity (or luminosity) is the density of the light flux that an illuminated surface emits. It is always equal to the luminous flux relative to the surface area. Luminosity also has its own unit, it is 1 lm / m 2 .
Uniformity of lighting
The luminous flux utilization factor is a method that allows you to calculate the uniformity of illumination of all surfaces horizontally, regardless of the type of fixtures. Its essence is that the coefficient is calculated for each room, taking into account its main parameters and the light reflection properties of finishing materials. This is a rather time-consuming calculation, not very accurate, however, this method is widely used when planning indoor lighting.
The volume of the room always has some kind of enclosing surface that will reflect the light flux coming from sources. This is a wall, ceiling, floor, furniture or equipment located in the room. All surfaces have different reflection coefficients, with a higher value or less. Calculate the number of lighting devices, not taking into account the reflected streams, it is possible only with large errors.
Estimated part
First, choose a lighting system and light sources, select the types of fixtures for a particular room - residential or working, and then calculate. Its purpose is to determine the number of fixtures. The calculation sequence can be performed according to this scheme:
1. The choice of lighting system.
2. The rationale for standardization in the lighting of this object.
3. The choice of the most economical light source.
4. The choice of a rational type of lamp.
5. Assessment of the safety factor of illumination and its unevenness coefficient.
6. Assessment of the reflection coefficient of surfaces in the room.
7. Calculation of the room index.
8. Determination of the coefficient in the use of light flux.
9. Calculation of the number of fixtures that will provide the required illumination of the object.
10. Sketch on the location of the fixtures using the floor plan (specify the dimensions).
Lighting system
It is especially difficult to calculate the working light, since it is most often combined. For example, in production workshops, local lighting alone is prohibited by law. The lighting system is chosen according to the smallest size of the object of discrimination, that is, guaranteeing the accuracy of all the visual work that will be carried out in the room.
The rules apply here: work from the first to the sixth category is performed only with a combined lighting system. This workshop is mechanical, tool, assembly and the like. Only in plants such as galvanic or foundry can a general lighting system be used. Therefore, choose a system and lighting standards at the same time.
Normalized Illumination
Artificial lighting by quantitative and qualitative indicators is determined in strict accordance with established and constantly applicable standards for this production and type of work.
The quantitative characteristic of illumination is taken at the smallest for each working surface, depending on the category of visual work, the contrast and background of the object in this lighting system. The category is determined by the size of the object (part), its part or the minimum defect on it, which the worker will have to detect and distinguish in his activities. Qualitative indicators of lighting are an indicator of blinding and a pulsation coefficient.
Light Sources: Pros and Cons
How to determine the parameters for choosing an economical and at the same time environmentally friendly light source? Many factors can influence a decision, such as a planning decision, architectural, construction parameters, air environment and its condition, economic considerations and, of course, design. The designer who designs the lighting always makes a compromise, taking into account many parameters when calculating.
For example, incandescent lamps are not very economical, they do not have very high light output, the radiation spectrum is distorted, during operation they heat up very much and quickly fail. However, their prime cost is very low, they are the easiest to operate, and therefore for rooms where people are temporarily staying, household and the like, incandescent lamps can be fully recommended. Luminescent ones have a luminous efficiency that is simply excellent, long service life, excellent color rendition, lack of heating. But such lamps are expensive and require specialist services. The starting equipment of fluorescent lamps is very complicated, they sometimes blink and make noise, and their disposal is problematic.