The power of visible light radiation, which is estimated by the sensation of the human eye and measured in lumens, is the luminous flux. This is the energy that any light source gives.
Wavelength
The light source transmits energy through emitted electromagnetic waves. The luminous flux is their speed, which gives information about the strength of the glow of a particular source. The human eye perceives the energy of light waves in different ways. A wavelength of 0.55 microns in green is perceived much stronger than in red with a wavelength of 0.63 microns. In the range of ultraviolet and infrared radiation, our eyes are powerless.
That is why the wavelength is so important to characterize the light flux. Taking into account the susceptibility for the eyes, summing the wavelengths, we obtain a normalized value. The luminous flux is the norm of the power of that radiant energy, which is estimated due to the sensation of light. Choosing for himself a source of light energy, a person is in accordance with its equivalent power. For example, if you need to replace incandescent lamps with LED ones. In this case, it is necessary to recalculate the power of the light flux.
How to do it
Luminous flux iskey indicator along the way. With the previous twenty-volt incandescent lamp, it was 250 lm. Exactly the same luminous flux of LED lamps can be provided with two or three watts, and fluorescent - with five to seven. So, the benefits of LED lamps are more than obvious.
Let's say we need 400 lm light sources. An incandescent lamp should be forty watts, a fluorescent lamp may have ten to thirteen watts, and an LED lamp only four or five. Or, for example, we need a powerful luminous flux of lamps - 2500 lm. An incandescent lamp cannot be less than two hundred watts in this case, a fluorescent lamp - only sixty or eighty watts, and an LED and 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 more than one hundred watts. But you need to know that the power of the lamp characterizes only the rate of energy consumption, it does not correspond to the concept of light intensity.
Here only a unit of luminous flux can characterize one or another 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, a note on the package: a luminous flux of 280 lm for a four-watt LED lamp, which is equivalent to a fifty-watt lampincandescent. We look at the table: the last luminous flux is not 280 at all, but all 560 lm should be. How come?
Calculations
The unit of luminous flux lumen is equal to the flux emitted by an absolutely black body with an area of 0.5305 mm2 at a very high temperature - 1773 °C, when platinum hardens, for example. The intensity of light is the density of the luminous flux in the spatial sense, it is important to consider how the luminous 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 a lumen, but a candela.
What is illumination? This can be called the surface density of the luminous flux that falls on a surface equal to the ratio of the luminous flux itself to the dimensions of the illuminated surface, where it is evenly distributed. Illumination also has its own unit of measurement, and this is again not lumens. And not even candela. This is a suite (lx). What will one lux be equal to if the luminous flux is equal to one lumen distributed evenly over an area of one square meter? But: 1 Lx \u003d 1 Lm / 1m2.
Brightness and luminosity
Light streams 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).
Luminance (or luminosity) is densityluminous flux emitted by the illuminated surface. It is always equal to the luminous flux relative to the area of this surface. Luminosity also has its own unit, it is 1 lm/m2.
Illumination Uniformity
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 luminaires. 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. These are rather time-consuming calculations that are not very accurate, but this method is widely used when planning indoor lighting.
The volume of the room always has some enclosing surfaces that will reflect the light flux coming from the sources. These are the walls, ceiling, floor, furniture or equipment in the room. All surfaces have different reflectances, with a higher value or less. It is possible to calculate the number of lighting fixtures without taking into account the reflected fluxes only with large errors.
Settlement part
First, the lighting system and light sources are selected, the types of lamps are selected for a particular room - residential or work, after which the calculation is made. Its purpose is to determine the number of fixtures. The calculation sequence can be performed according to this scheme:
1. System selectionlighting.
2. Justification of normalization in the illumination of this object.
3. Choosing the most economical light source.
4. Choosing a rational type of lamp.
5. Estimation of the illuminance safety factor and its non-uniformity coefficient.
6. Evaluation of the reflection coefficient of surfaces in the room.
7. Room index calculation.
8. Determination of the coefficient in the use of luminous flux.
9. Calculation of the number of fixtures that will provide the required illumination of the object.
10. Making a sketch of the location of the fixtures using the floor plan (specify dimensions).
Lighting system
It is especially difficult to calculate working lighting, since it is most often combined. For example, in production shops, local lighting alone is prohibited by law. The lighting system is chosen according to the smallest size of the object of distinction, that is, guaranteeing the accuracy of all visual work that will be performed indoors.
Norms apply here: work from the first to the sixth category is carried out only with a combined lighting system. These are mechanical workshops, tool workshops, assembly workshops, and the like. Only in industries such as electroplating or foundries can a general lighting system be used. Therefore, they choose the system and the norms of illumination at the same time.
Normalized illumination
Artificial lighting in terms of quantitative and qualitative indicatorsdetermined in strict accordance with the established and permanent standards for a given production and type of work.
The quantitative characteristic of illumination is taken as the smallest for each working surface, depending on the category of visual work, contrast and background of the object in a given lighting system. The category is determined by the size of the object (detail), its part or the minimum defect on it, which the worker will have to detect and distinguish in his activity. Lighting quality indicators are glare and flicker.
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 the decision, such as: planning solution, architectural, building parameters, air environment and its condition, economic considerations and, of course, design. A designer who designs lighting always compromises, taking into account many parameters in the calculations.
For example, incandescent lamps are not very economical, they do not have a very high light output, the emission spectrum is distorted, they get very hot during operation and quickly fail. However, their cost is very low, they are the easiest to operate, and therefore for rooms where people stay temporarily, household and the like, incandescent lamps can be recommended. Luminescent ones have simply excellent light output, long service life, excellent color reproduction,no heating. But such lamps are expensive and require specialists to maintain. The triggering equipment for fluorescent lamps is very complex, they sometimes flicker and make noise, and their disposal is problematic.