To save energy in lighting systems located in areas at risk of potentially explosive atmospheres, it is possible to decide to intervene by automatically switching off the devices after a certain number of hours or, where possible, by reducing the luminous flux [1] at the outlet. 

 Until a few years ago, traditional light sources, such as discharge lamps or fluorescent tubes, were not suitable for managing the output light flux because these types of optical sources worked optimally at specific nominal power values. Often, the partialization of the light flux occurred with circuits that had an imprecise regulation, produced flickering or, when they worked, did not lead to significant energy savings (this is the case of the rheostat coupled with the incandescent lamp). In this field too, the advent of LED technology has brought about a real revolution.

Explosion-proof floodlights of the SLED-ME-… series, available on request with 1-10V or PWM dimming

LED lighting fixtures consist of an electronic power supply and an LED plate. The LED plate is the light source that emits the light, and the luminous flux is proportional to the current passing through it. 

 It is easy to integrate in the driver a system that manages the output current towards the LED plate in a proportional or correlated way to a specific input (dimmer circuit). Through this system we can therefore precisely partialize the light output from a lighting fixture. Drivers equipped with this feature are called dimmable and the lighting fixtures built with these drivers are also called dimmable.

The simplest systems for dimming LED lamps use an input that is proportional to the light output of the device. This input can be a voltage between 0-10V or between 1-10V or it can be a square wave that is modulated through its Duty Cycle [2] (PWM dimming type). 

The advantage of these systems lies in a quite simple control that can be achieved economically or with analog components (a variable resistance potentiometer is often directly applicable to 0-10V and 1-10V systems). On the other hand, the main defect of these types of dimming lies in the fact that you act simultaneously on many devices with the same command and therefore you cannot differentiate by zone in an effortless way using a single circuit. 

In addition to these simpler systems there are much more sophisticated ones, among which the DALI standard is the most famous from a commercial point of view.The DALI standard consists of at least one controller and a power supply network and can integrate sensors and buttons on the same line. 

Unlike simpler systems, communication on the DALI network can be bidirectional, the lighting fixtures have an address and each of them can be controlled independently by the others. This also results in a smaller number of cables for the creation of the bus [3]. It is also possible to integrate lighting fixtures that use 1-10V or 0-10V dimming into DALI systems with special signal converters.

With the development of LED lighting products suitable for use in areas classified as being at risk of potentially explosive atmospheres, Cortem has made floodlights, linear lighting fixtures and high bays with several types of dimming. 

In this way, even in dangerous plants it is possible to implement energy saving strategies that at the same time reduce the operating costs of the plants and minimize their environmental impact. 

Reference standards and bibliography

[1] The luminous flux coming out of a lighting fixture corresponds to the power coming out in the form of light radiation. Light, in fact, is nothing more than electromagnetic radiation contained in a certain range of wavelengths and, like every type of radiation, carries with it a certain amount of energy. The luminous flux is not measured in Watts but in Lumens, that is, a measure of the luminous power as it is perceived by the human being (each frequency contained in the light spectrum is weighted according to a value that recalls the perception of the human eye). 

[2] Duty Cycle means how long the high signal lasts in relation to the duration of the signal.[3] In electronics, bus is a generic term that indicates a shared "channel" for the exchange of information, signals, addresses or power.