Fineline Solutions was asked to design a LED lighting system for a large chandelier, which was to be used in the Sochi Olympics ceremonies. The system had a number of requirements:
- 1,247 LED candles spread across 17 levels
- Candles must look as realistic as possible, i.e. flicker just like a real candle
- Candles must be dimmable via DMX
- Flicker speed must be adjustable via DMX
- Power consumption should be minimal
- System should be easily assembled and disassembled
- Cables between levels should be kept to a minimum
- Electronics must be rain-proof
The chandelier itself will be flown inside the stadium, and when opened, will be over 22m in height. Power and control signals will be fed from the top of the structure, however DMX control components must be situated on one of the lower, more accessible levels.
Research and prototype
Initially, a degree of research was undertaken to find out whether suitable LED flickering candle lightbulbs were already available on the market, and whether they were suitable for use in this project. Although LED flicker candle bulbs are available from some sources, they were not suitable for use, mainly due to size and lack of dimming control.
As a result, a prototype was developed to realise the project objectives. The prototype unit used a total of six Luxeon LEDs per candle, three on each side of the PCB. The LEDs were driven as three strings of two, using a constant current LED driver. This driver device allowed the LED current to be set by way of an external resistor, and also for the brightness to be varied by a pulse-width modulation (PWM) input.
The initial prototype indicated that the LEDs chosen were a little too bright for the application, and also indicated that heat from the driver and LEDs would be an issue at this brightness. A more suitable value for the current limit resistor was chosen.
In order to produce a flickering effect similar to a real candle flame, it was necessary to develop a pseudo-random number generator which could be used to determine whether to illuminate an LED or not. A separate portion of the random number was used to drive each candle, ensuring that the pattern was not repeated.
The prototype controller was also developed to receive and buffer DMX data. Two DMX channels were used: one to control the brightness, and one to control the flicker rate. A standard DIP switch arrangement was used to allow the DMX start channel to be changed.
Once the prototype had been demonstrated and approved, it was necessary to design the components used in the final installation. The chandelier consists of 17 levels, each of which employs candles of differing heights. Candles are grouped together in groups of 12 on the lower levels, and groups of 6 on the upper levels, using decorative metalwork to make a candelabra. At the bottom of the chandelier, the candelabra were over 1m tall, whereas the highest candelabra were only 150mm in height.
The controller was designed to control up to 24 separate candles, i.e. a total of 144 LEDs per controller. A custom PCB was produced to fit into the lid of a suitable waterproof enclosure, providing an RJ12 socket to connect to each candle. The controller board employed a single microcontroller to receive DMX data and to control the brightness and flicker rate of each candle. A total of 48 controllers were required throughout the structure.
A separate 12V DC power supply was required for each controller. To reduce the weight associated with cabling, it was decided to have a larger number of small power supplies, rather than a single central high-current supply. This approach also ensured that the effects of a power supply failure would be minimised.
Each candle consisted of six LEDs, mounted on either side of a suitably-sized custom-made PCB. Each PCB was also equipped with an RJ12 connector, allowing the candle to be connected to the controller using standard cabling. One particular challenge was to accommodate the various different candle sizes – it was not possible to produce a single PCB that could be used everywhere in the structure. In addition, the size of the RJ12 connector became a significant problem for higher levels – with candles only 7mm wide, an RJ12 connector was difficult to accommodate. Fortunately, it was possible to lose the bulk of the connector into the structure, effectively hiding the connectors from view.
Each candle was also equipped with a moulded plastic ‘flame’, which was secured over the top of the PCB. This flame was designed and modelled by our sister company, Fineline Manufacturing. Five different sizes were produced to deal with the differing sizes throughout the structure.
Prior to installation, each candle PCB and controller PCB was tested, and the controllers programmed. Due to the nature of the structure, it was necessary to make up custom cables to connect between the controller and candles. In addition, mains and DMX cables needed to be provided throughout the structure, with suitable connectors to allow it to be disassembled for shipping.
One of the biggest challenges was finding a venue with sufficient height to fully hang and test the chandelier prior to shipping to Sochi. The chandelier was assembled at Earls Court in London, although at the time, not all levels had been wired at this time. Wiring and testing work was completed prior to shipment to Sochi, allowing the structure to be assembled with relative ease by the on-site team.
For further information, or to discuss a similar project, please contact Fineline Solutions.