Low Power LED Circuit Design Yavor Gegov ( 1007459) Supervisor: Scott Roy

University of Glasgow, charity number SC004401

2.Project Objectives : • Improve on the work done in previous projects. • Fit the device in a standard wall mount pattres box. • Meet real world lighting requirements in a demanding

environment. • Introduce a back up power source, such as an on board

battery. • Introduce support systems that will ensure the long lasting life

of all components used. Such as powered cooling for the LEDs.

3.Lighting Requirements : The previous work on the project was carried out with modest illumination requirements. For this iteration and attempt was made to fulfil the requirements of an office space .

Taking into account light absorption in the environment. A lumens target of 2200 was determined. This considerable step up caused substantial complications in every aspect of the design mostly due to the packaging constraint of the pattress box.

4.Electrical Design and Electrical Packaging : The LEDs are separate in 2 groups ( lighting and emergency ) . Each group requires a supply of 37V and 1.2A which called for the use of a MOSFET to by pass the boost converters build in switch in order to prevent device meltdown. In order for the system to also be DALI compatible a MBED microcontroller was utilised. The microcontroller is powered through a buck converter which improves the system efficiency compared to the previously used linear regulator. Two connection ports which can be powered or not are included in the design. Through the use of optocoublers the design is in theory compatible with other control schemes.

5.Mechanical Design : Using the pattress box meant that the device was left with only the top surface to emit light from and also do any cooling work. This called for breaking up the system into 2 levels .

6.Cooling design : Due to the devices geometry a fan was chosen as the best way to cool the system.

7.Conclusion : All packaging and performance requirements were met. The device remains to be tested in its final form with all features running.

1.Introduction : Digitally addressable lighting although more complex offers substantial savings during a system`s lifetime and offers an environmentally friendly alternative to ordinary lighting. This project aimed to build a DALI [1] style LED lighting fitting.

8.References : [1] -Digital addressable lighting interface British Standards Institute, BS EN 62386-102:2009

Fig.1 : Office Floor lighting , values in Foot Candles

Fig.2: DALI slave schematic Fig.3: DALI slave PCB layout

Fig.4 : Mechanical design Isometric and top view

Fig.5 : Thermal flow simulation.