Frequently Asked Questions click to view full questions and answers

Explain the different Lighting Communication Terminologies
What are the features found on a touch screen?
What is a touch screen?
What other methods could you use for scene setting?
How would you use a user interface?
What products would you use to program lighting scenes?
What is scenesetting?
How do you dim fluorescents?
What the advantages of adaptive dimmers
What is a transistor dimmer?
What are the concerns with electronic transformers?
What is an inductive load?
What is the difference between triac and thyristor dimmers?
How does a dimmer work?

Within the lighting industry there are many names, codes and acronyms that are used to describe the communication between lighting control devices. Some are industry standards others are manufacturer specific. Below is a means of removing the mystery and defining how different market segments use different communication means.

Fluorescent ballast control
There are 3 means of controlling fluorescent ballasts. Two of which are industry standards, the other from a single manufacturer.
·1 – 10V
This still remains the standard means of controlling the light level of fluorescent ballasts. Ballasts with this control incorporate a dimming circuit controlled by an analogue 1 – 10VDC control voltage (EN60929 standard). Mains power to the ballast is switched separately and externally to the ballast.
·DSI
This is digital ballast control from Tridonic. The primary advantage that DSI ballasts have over the 1 – 10V control is that they have an internal electronic power switch. By using the digital control pair, the power can be switched on/off as part of a control message. This removes the requirement to separately switch the power supply to the ballasts.
·DALI
DALI is short for Digital Addressable Lighting Interface. The major European ballast manufacturers have devised this standard and it offers similar benefits to DSI.
These ballasts offer integral controls and scene setting functions. However a DALI system requires addressing of each ballast or device and each network is limited to a maximum of 64 DALI ballasts or devices such as control panels and sensors.

Audio Visual Integration
The Recommended Standards (RS) below are purely the means of communication not the message / protocol. DMX, for example, uses RS485 as the bus with the DMX being the protocol. Many manufacturers use the RS buses and have there own protocols written in either hex code or ASCII characters.
·RS232
RS232 offers simple point-to-point communication between two devices at relatively slow data rates (up to 20K bits/second) and short distances up to 15m.
·RS422
RS422 (differential) was designed for greater distances and higher Baud rates than RS232. Data rates of up to 100K bits / second (Baud) with distances up to 1200m can be accommodated with RS422. RS422 is also specified for multi-drop applications where one driver is connected to, and transmits on, a "bus" of receivers.
·RS485
RS485 is similar to RS422 in terms of data rates and distance but allows multiple devices to talk to each other rather. RS485 has generally replaced RS422.
Entertainment lighting control
·DMX512
DMX512 is the internationally accepted standard of communication for entertainment lighting products, such as control desks, dimmer packs, moving lights and colour scrollers. As the standard DMX512 implies, there are 512 control channels available on a single network and the protocol runs on a RS485 bus at 250K bits / second (Baud) at 750m.
·ACN
Advanced Control Network (ACN) is a new control protocol that will run on a standard Ethernet bus. It is currently in the design process in the United States.

Integrated bus and protocol systems
There are a number of integrated bus and protocol systems that are used across the building industry. Below are the systems that are also used by the lighting industry. All of them offer distributed control; i.e. there is no central control system, each device on the network is part of the intelligence collective. They are all open standards, i.e. the protocol is easily available and open to a manufacturer to produce compliant product.
·CAN
CAN is an acronym for Controller Area Network. This is a bus system developed by Robert Bosch GMBH, for use in the automotive industry. Because it was developed to work in highly hostile environments, it is intrinsically stable and reliable.
It is now used by a number of lighting control manufacturers due to its reliability and cost effectiveness.
·LonWorks
Echelon’s LonWorks platform is an open standard for control networks. LonWorks can be made up of a variety of LonWorks compliant products linked together on the same LonWorks network.
LonWorks is used in factory and building automation.
·EIB
European Installation Bus (EIB) is widely in continental Europe for building automation, both commercial and domestic. Insta is a collective of German electrical accessory manufacturers who make a variety of EIB control components.

Full graphical “tell back” control of each and every circuit within an area.
Integral Astronomical time clock.
Virtual fader control for manual operation of circuit levels.
Hidden page and function capability. This will provide (for example) a hidden programming page for the lighting designer to program pre-set scenes.
An automatic screen fade down function which reduces the screen brightness automatically to a non-intrusive level after a programmed time out period.A programmable “return to welcome page” function.
Help pages.
The LCD touch screen communicates directly with the iCANnet™ network. Messages are both transmitted and received, allowing remote monitoring of control panels and sensors.

In this method of control all manual, scene set, time clock and graphical control can all be integrated into one simple control panel. The LCD touch screen is a flexible device which provides an intuitive "user friendly" method of interfacing to the lighting control system. The LCD touch screen provides virtually a limitless flexibility of system configuration and control.
This method of control is ideal for areas where complex and flexible control is required. It is completely software based, and programs can be tailored to suit the precise needs of the user. It also offers many advantages over conventional control panels not least of which are multiple control functions. For example in a hotel suite, these units can be programmed to control the lighting, the motorised curtains, the air conditioning, the TV, and any other device that is fitted with the appropriate control interface. The screens can be programmed in a highly graphical way to guide the user through what they should do to achieve the desired result. This is particularly useful where users have a variety of languages or levels of skill.

Other methods of accessing the preset scenes are from LCD touch screen controllers, time clock, PE/PIR units, wireless remote hand held controls, central PC controllers with remote access and Audio Visual and Home control systems, as well as Building Management Computer systems.
Time Clocks and PE/PIR Photo Electric/Passive InfraRed units enable the scene selection process to be automated. This method ensures that the correct scenes are set at the appropriate time of day and day of the week.
PE/PIR units allow scenes to be triggered or selected automatically, depending on ranges of natural light intensities or by persons entering a room or area in a building.

The user interface to the scene setting is usually by means of a push button control panel, mounted at a logical position within a room. In many applications there will be several controls operating in parallel. Each button cap is back illuminated when active, and will invariably have a legend with the name of the scene.

The programming of the lighting scenes is done using either the control panels themselves, a hand held programmer which is removed once the programming is completed or a laptop computer with dedicated programming software (iCANsoft™). The secure memory facility in the iCAN™ source controllers provides a capacity for over 128 scenes, which is more than adequate for even the most demanding of installations.
There are very many different applications for the scene setting approach

In the theatrical sense a scene takes place in a dramatic context, hence the expression setting the scene (or in an architectural sense, setting a mood). As the story unfolds, so the look and feel and structure of the scenes within a play will change. The lighting is a fundamental part of this mood setting. Indeed the Set in a play may remain unchanged through a complete act, but as part of the illusion process in theatre, the lighting directs our attention to where the action is. Clever and creative use of lighting in theatre enables very basic Sets to be dramatically manipulated to spectacular effect by the director.
The same principles of lighting apply in an architectural application

The method of dimming of fluorescent lamps is dependant on the type of dimmable ballast being used. This is dealt with in greater detail in the technical information Section entitled ”Load Compatibility“. Note however that there is a vast array of different fluorescent lamps available. As a general rule, only those with 4 pins are dimmable. Furthermore, they must be supplied with ballasts that are electronically dimmable. Whilst there are still some mains voltage dimmable ballasts available, in general terms these are either themselves prohibitively expensive or do not comply with CE directives on EMC, Safety or the Low Voltage Directive. Use of the latter devices within the EU is illegal.
iLight™ has a range of HF Ballast controllers that are compatible with all commercially available dimmable ballasts available in the EU.
As a rule these fall into three types:- The most common units require the mains supply to be switched on or off, and the intensity of the lamp is determined by a control voltage in the range 1->10 volts.
The second popular ballast is the digital ballast available from Tridonic. These are referred to as DSI ballasts. The primary advantage that these ballasts have over the 1->10-volt units is that they have an internal electronic switch. By using the digital control pair, the power can be switched on/off as part of a control message. This removes the requirement to separately switch the power supply to the ballasts. Finally, there are DALI ballasts. These will become commercially available in early 2001. In theory these ballasts offer integral controls and scene setting functions. In practice the concept requires a random addressing of each ballast. This would mean that commissioning or maintaining installed systems would be difficult and expensive. Each network is also limited to a maximum of 64 ballasts. It is understood that most ballast manufacturers will be offering units with both 1->10 volt control as well as DALI.

iLight™ has developed an FET (field effect transistor) source controller that solves all the load compatibility problems inherent in loads controlled by both triac and transistor dimmers.
In the iLight™ Adaptive Dimmer, both the voltage and the current are monitored, and this is linked into the CPU which controls the dimmers operating parameters. This control is dynamic and offers several major benefits over conventional dimmers.
These adaptive source controllers will work with resistive, capacitive and inductive loads. They will also detect reactive loads. If a reactive load is connected to the dimmer, it will immediately switch to full on, thus avoiding any possible damage to the gear associated with that circuit. Alternatively, the unit can be configured to switch off, if that is the user preference.
When the adaptive source controller “sees” an inductive load, it adopts a leading edge dimming mode. Furthermore the patented iProtect™ circuitry within the source controller can determine if the load is too great for it to cope with. In this case the unit will immediately switch off. However, in the case where the lamp inrush current is the reason for the overload* the dimmer will attempt to turn on every half cycle. Each time it tries a small amount of energy is transmitted to the lamps. This energy has the effect of warming up the lamp filament. As the temperature rises, so does the resistance of the lamp, thus reducing the current passing through the filament. After several cycles, the filaments will have heated up sufficiently to offer sufficient resistance and so the monitoring circuitry within the source controller will allow full control or illumination of the lamps.
Should the adaptive source controller identify a resistive or capacitive load, then it will adopt a trailing edge dimming methodology. This has the added benefit that the unit will be then totally silent in operation - because trailing edge dimming techniques result in there being no magneto-striction in the suppression chokes (used for RFI (EMC) suppression).
The other major advantage of this technology over conventional dimmers is that the speed of “turn on” can be precisely and dynamically controlled. In entertainment lighting, there is a requirement to be able to flash lights on very quickly. However, when theatrical lamps are turned full on instantly, the filaments suffer thermal shock. This shock reduces the life of the lamp. By optimising the turn on time in a dynamic way, the fastest possible turn on times may be achieved whilst minimising the thermal shock to the lamps and thus dramatically extending lamp life.

A number of dimmer manufacturers produce transistor based dimmers which operate in a different fashion to triac dimmers making it compatible with electronic (capacitive) transformers even if they are not designed for dimming applications.A transistor dimmer switches the supply off and is commonly known as a trailing edge dimmer. By switching the current off the possibility for voltage peaks is eliminated.

Unlike wire wound transformers, which by their very nature are dimmable, electronic transformers may induce problems and care must be taken when selecting electronic transformers to ensure compatibility with dimmers in a control system.
Almost all dimmers in the UK employ triac or thyristor pair circuitry to control the mains voltage sinusoidal waveform which reduces the energy flow and hence the light output in a lamp.A triac dimmer switches the supply on and may be known as a leading edge dimmer. When used with an electronic transformer that has a capacitive nature, an amount of overshoot can occur resulting in higher than normal peak-to-peak voltages.
A transformer that has been designed for use with triac dimmers should not produce these peaks. A transformer that is not designed for triac dimming may work but is likely to emit audible noise when dimmed. This noise is usually a symptom of internal stress, which in turn can cause failure of the transformer. This problem will become worse with more fittings on a circuit.

The above examples hold true for mains voltage tungsten loads but low voltage fittings introduce a transformer into the circuit that makes the load more complex. With a mains voltage incandescent lamp, which has a resistive characteristic, the voltage and current waveforms are almost identical. On the other hand, a wire wound transformer is an inductive load and the current tends to lag behind the voltage. Once triggered a triac or thyristor relies on the current flowing through the device to keep it conducting. Should the current fall below the device’s threshold level it will turn off and stop conducting. However with an inductive load the current ’lags‘ behind the voltage so it is possible that the current through the triac will not reach the triacs threshold level before the trigger pulse ends. This results in unacceptable dimming performance. To avoid this, dimmers designed for use with wire wound transformer fed loads use what is known as a hard firing technique. This ensures that the trigger pulse is maintained for a long enough period of time to ensure that the current reaches the device’s threshold level.

Triacs and thyristors are similar components; a triac is essentially two thyristors combined in one package. Thyristors tend to be more expensive but more robust. Triacs have the advantage that they are less likely to “half wave” on failure and so the opportunity for headache induced (50Hz) flickering and subsequent damage to transformers is greatly reduced. Furthermore, when triacs are over-rated, they offer a technically more elegant solution than thyristors.