LED lighting in the home is becoming more popular due to the energy and money saving benefits it offers over traditional halogen lighting. One of the most common problems that an electrician faces when installing LED’s is enabling them to dim.
Resistive dimming has become a standard way of dimming halogen lighting and it works by reducing the voltage allowed to the bulb with a variable resistor.
A resistive dimmer switch is easy to install because it is simply wired between the mains (240V) power and the bulb, however whilst the lighting is dimmed the voltage resistance is converted to heat and is not considered energy efficient.
Note: LED’s cannot be dimmed using resistive dimming; it will slowly damage the LED’s.
Pulse-Width Modulation Dimming
Pulse-width modulation works by switching the voltage on and off at a variable speed. This causes a flickering effect that is too quick for the human eye to see. By increasing and decreasing the switching speed it increases and decreases the max possible light output and dims the LED.
A problem found with PWM dimming is as the amount of dimming increases so does the amount of time the voltage is turned off. This will eventually fall within the flickering speed in which the human eye can see.
This flickering can normally be seen when the LED is dimmed to below 10% of its original light output.
A TRIAC (Triode for Alternating Current) dimmer works by conducting the current in both directions, alternating at a variable speed. This makes the switching much faster than Pulse-width modulation dimming so it never goes within the flickering speed of the human eye.
Both PWM and TRIAC dimmer modules require a signal to tell the dimmer how much to dim the LED’s. The current standard is 0-10V.
0-10V signals work by sending a separate 10v signal to the PWM/TRIAC dimmer module and then using a resistive dimmer to reduce the voltage on the 10V signal. As the voltage drops the dimmer module reduces the brightness on the LED’s in relation to the voltage.
10V = Dim at 100%
8V = Dim at 80%
3V =Dim at 30%
DALI is an open source 2 way protocol designed for controlling lighting in the home. It is a royalty free standard meaning it is possible to mix and match DALI module’s from different manufactures. DALI works by assigning zones and linking all the DALI modules for each zone together.
The DALI controller can then control multiple zones individually.
The DMX 512 protocol was originally designed to control nightclub and theatre lighting and has only recently started to be used in the home.
This means that each dimmer module is given a DMX address so it knows which channel to read and adjust the brightness accordingly. Each dimmer module has a DMX In and DMX out socket so the data signal can be daisy chained from one module to next.
DMX can control colour changing lighting as well as non-lighting devices. E.G. Fog machines, Blinds and even motorised doors.