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Research and Education on Lighting Laboratory. D.Sc. Eino Tetri Lighting Laboratory. Helsinki University of Technology Department of Electrical and Communications Engineering Staff: 23 people working in education and national and international research projects

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Research and Education on Lighting Laboratory

D.Sc. Eino Tetri

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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

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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

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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

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Lamp Life of T5 Fluorescent Lamps in Dimming Use


  • 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

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  • 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

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Electrical measurements

Average electrode temperature

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  • Temperature measurements with infra-red camera

  • Hot spot temperature

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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

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Electrode temperature vs. voltage after 15 000 h

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  • Mortality after 20 000 burning hours

  • Average electrode temperatures, hot spot values higher

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  • 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

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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

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Modular LED-PLC Lighting System

CCT Control Using the Forward Voltage

Arrangement of the LEDs on the MCPCB

LED luminaire prototype

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Experimental setup


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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)

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  • 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