BECKHOFF DK9222-0310-0010 - Manual

I/O
Bus Terminals
Application Note DK9222-0310-0010
Keywords
Lighting control
Universal dimmer
Low-voltage halogen dimmer
Ethernet dimmer
Leading edge phase control
Trailing edge phase control
Short-circuit-proof
Network-capable
KL2751
KL2761
Basic principles of the dimmer function and network
capability
This application example describes the basic principles of the dimming of light, the important aspects
concerning the individual types of dimmer (leading edge phase control, trailing edge phase control,
universal) and the advantages of the use of a network-capable universal dimmer.
Basic principles
In order to dim the intesity of a light bulb, the flow of current is reduced, which corresponds to a regulation of the brightness.
Three principles can be employed for this: voltage divider, leading edge phase control and trailing edge phase control. The
voltage divider is not used because of its energetic inefficiency: the voltage for the light generation is divided by an adjustable
pre-resistor; the proportion of the unused power to generate light is dissipated by the resistor and converted into heat energy.
Phase control dimmers work considerably more efficiently, since in this case the current is switched on and off by means
of electronic circuits. The light bulb is switched at a frequency that is not discernable to the eye. Since the flow of current is
interrupted during the dead time, the power dissipation is considerably reduced in comparison with the voltage divider. The
ratio of the switch-on time to the switch-off time determines in both principles the flow of current or the quantity of emitted
light. The basis of both principles is the sine wave of the mains voltage. At a frequency of 50 Hz the voltage changes its polarity
100 times per second; it therefore also reaches the zero crossing point, at which there is freedom from both current and
voltage for a brief moment, 100 times per second.
Dimmer types
Electronic phase control dimmers control the effect produced by the light source by only letting the current flow over a certain
section of the alternating voltage half-waves. In the case of 230 V general-purpose lamps (‘incandescent lamps’), the operating
New Automation Technology Beckhoff 1
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