Abstract
The colour appearance of light sources has a major impact on how people perceive space. With LED illumination lighting, the colour output can be tuned to virtually any perceivable colour, including any hue of white light. It has been established that the right shade of white light during the 24-hour day cycle has a positive effect on the human body's biological system. For this reason, it is very important to focus on the development and application of new lighting systems that have dynamically variable light outputs in order to imitate the sunlight. Circadian regulation is most responsive to short-wavelength light (460 nm = blue colour).
 This paper describes the development of a low-cost extra-low voltage LED dimmer for tunable white lighting systems aiming to achieve maximum electrical performance and light-output. This dimming module has two independent LED control channels and allows for a variable colour temperature control from warm white to cold white light. Experimental results of the dimming module efficiency measurements, correlated colour temperature (CCT), colour rendering index (CRI), illuminance and power consumption of the luminaire depending on the duty cycle for different control frequencies (200 Hz, 1.5 kHz, 5 kHz, 10 kHz and 20 kHz) are presented. The paper further describes the principle of creating control curves for an independent regulation of correlated colour temperature and illuminance. In the form of a table, the control curve outputs may be uploaded into a microcontroller. The paper details the construction, function and the advantages of this LED dimmer prototype.
Highlights
Artificial lighting has contributed to changes in people’s lifestyles
This paper was supported by the following projects: LO1404: Sustainable development of ENET Centre; SP2019/159, SP2019/28 and SP2019/65 Students Grant Competition and TACR TH02020191 and TACR TH777911, Czech Republic and the Project LTI17023 "Energy Research and Development Information Centre of the Czech Republic" funded by Ministry of Education, Youth and Sports of the Czech Republic, program INTER-EXCELLENCE, subprogram INTER-INFORM and project TN777901 National Centre of Energy
The LED dimmer consists of the following main components: a power supply (IRM-45-48ST, 45 W, 230 V AC/48 VDC, 0.94 A) [12], STM32L011F4P6 low-cost 32bit microcontroller, two ILD6150 dimming LEDs drivers, VS1838B IR receiver sensor, RT9068-33GSP voltage regulator, optocouplers and a RS485 serial interface
Summary
Artificial lighting has contributed to changes in people’s lifestyles. People are more active during the night than they used to be. Three types of temperature changes in LED lights are used: Dim to Warm, Tunable White, and Full-Colour Tunable. The technology of mixing white-warm and white-cold light colour (Tunable White) uses two LEDs, one of a whitewarm colour and one of white-cold. Lights with correlated colour temperature control (tunable white) are equipped with LED chips of varying correlated colour temperature controlled by special power supplies. Such sources are controlled using different user’s interface. The correlated colour temperature control options are extended by different producers so that the lights could be used for any everyday activity. The cost of the tunable white technology lights widely differs in dependence on the principle of the applied solution and producer. This paper describes the practical implementation of a LED dimmer prototype, including the measured lighting characteristics in dependence on the electrical properties of the dimmer
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