1. Research and Education on Lighting Laboratory D.Sc. Eino Tetri eino.tetri@tkk.fi

2. Lighting Laboratory • Helsinki University of TechnologyDepartment of Electrical and Communications Engineering • Staff: 23 people working in education and national and international research projects • Research and education include areas related with light, lighting and electrical building services

3. Research Areas Indoor Lighting Office lighting systems Artificial lighting and daylighting controls Lighting and productivity Visual performance Daylighting glare measurement User perspectives and requirements Traffic Lighting and Vision Road and street lighting Vision at low light levels Spectral sensitivity in the mesopic range Visibility of flashing lights Signal lighting Road and street lighting measurements Light Sources and Energy Characteristics of lamps and ballasts The effect of dimming and cathode heating on lamp life The use of LEDs in lighting The electricity use of lighting Lighting Measurements and Testing Spectrum and colour measurements Photometric calibrations Outdoor and indoor lighting measurements Motor vehicle, road traffic lamps and retro-reflectors, aeronautical and maritime lighting devices Electrical Building Services Home and Building Electronic Systems Home Automation and Networks Building Automation

4. Doctoral thesis being prepared • Henri Juslen: Benefits of the lighting for industry - case studies in industrial environment • Pasi Orreveteläinen: Perception of visual signals in peripheral vision (2005) • Jaakko Ketomäki: The effect on bright light sources to the contrast sensitivity in the central and peripheral vision • Marjukka Eloholma: New mesopic scales based on night-time driving performance (2005) • Viorel Gligor: Lighting quality and productivity in office lighting • Tapio Kallasjoki: Lighting renovations in offices in order to improve lighting quality and energy efficiency • Meri Liesiö: Development of performance based mesopic photometry • Liping Guo: Lighting control in street lighting • Pramod Bhusal: Lighting efficiency in buildings • Paolo Pinho: Usage and control of LEDs for plant applications • Oskari Moisio: Usage and control of LEDs in general lighting

5. Lamp Life of T5 Fluorescent Lamps in Dimming Use Objectives • The effect of dimming on lamp life • The optimal electrode heating in dimming use • The electrode should be at a high enough temperature to produce sufficient electron emission, but not so high that there is excessive evaporation from the emitter

6. Introduction • The electrode temperature determines the rate of loss of the electrode emissive coating • Electrode temperature directly affects the lamp life • The electrode temperature in dimming use is maintained by an additional heating current

7. Measurements Electrical measurements Average electrode temperature

8. Measurements • Temperature measurements with infra-red camera • Hot spot temperature

9. Lamp life test • 8 test group, 24 T5-lamps in each, 28 W • Dimming level: 100 %, 15 %, 5 % • Electrode heating level nominal, decreased or increased • Burning cycle 24 h, 23 h 45 min ON, 15 min OFF • In addition some special lamps with no fluorescent powder near the electrodes

10. Results Electrode temperature vs. voltage after 15 000 h

11. Results • Mortality after 20 000 burning hours • Average electrode temperatures, hot spot values higher

12. Conclusions • The electrode heating should be high enough in dimming use to ensure the adequate cathode temperature • The electrode voltage with T5 28 W lamps should be more than 7 V and the average electrode temperature more than 700º C • Results show that with proper electrode heating T5 lamps can be dimmed without decreasing their lamp life

13. RET - Energy performance of buildings • Implementation of the Energy performance of buildings –directive (2002/91/EC) • The aim is to improve the energy-efficiency of the buildings by defining the indicators for energy-efficiency and by developing the calculations methods

14. Modular LED-PLC Lighting System CCT Control Using the Forward Voltage Arrangement of the LEDs on the MCPCB LED luminaire prototype

15. Modular LED-PLC Lighting System

16. Subjective preferences for LED Lighting

17. Experimental setup CF LED Inc

18. Test persons Normal colour vision (not tested) 8 wear glasses in Exp I and 11 in Exp II Different nationalities (10 Exp I, 4 Exp II)

19. Photometric values

20. Spectral power distribution

21. Test questionnaire

22. Results, general preferences Test 1 Test 2

23. Results, colour chart Test 2

24. Conclusions • With a good setup the perception of light from LEDs improves and people are more likely to prefer this light when compared to incandescent and fluorescent light. • The rendering of the skin color under the LEDs light is not very well accepted. • The colour rendering index does not predict the subjective preferences