Dimming LEDs is not as simple as dimming incandescent bulbs used to be, but by following our guidance it’s a great way to make even bigger energy savings and control your lighting environment.

First things first 

1)     Make sure that the LED panel, or more specifically the driver, is dimmable. Most LED panels are sold with a non-dimmable driver, as a dimmable driver must include more electronics which adds cost.

2)     Choose the dimming method.

Dimming methods

Mains Dimming:

This will be familiar to many people, as it’s the method generally used in homes. Mains dimmers tend to be rotary and are what you would find on a wall in place of a light switch. They have a knob you can twist anticlockwise or clockwise to decrease or increase the light output and push in to switch the light on and off.

Mains dimming works by chopping up the electrical signal from the mains. It does this by switching the electric current on and off several times a second. The result of this rapid switching is that less power is available to the light as the power is off for part of each second.

The light is on and off at full power, but less light is delivered in total compared to if it was on the whole time. Since our eyes cannot process the rapid switching, our brain interprets this as a steady, dimmed light source.

The power from the mains in the UK comes in a wave with a frequency of 50Hz. That means this wave is repeated 50 times a second. As the current from the mains is alternating, switching from positive to negative every cycle, there are 100 cycles of current per second: 50 positive and 50 negative.

Mains dimming is achieved by switching off the power for a period twice in every wave, one for each cycle of current.

Mains dimming can be split into 2 types – Leading Edge and Trailing Edge, but it’s not necessary to worry about this as the Varilight V-PRO dimmers we recommend for all our LED Panel TRIAC dimmable drivers, are compatible with either, Leading Edge, or Trailing Edge drivers.

Choice of dimmer power

When LED drivers are first switched on, they draw a large amount of current for a very short time, until the capacitors inside them have charged. This is known as “in-rush”. This does not change the overall power consumption at all, so LEDs are still big energy-savers, but it does mean that a dimmer will “see” them as having a higher wattage.

LED dimmers, therefore, are de-rated for use with LED products. This means that while the dimmer may show a rating of 400W, the LED dimming rating could be 100W. Please therefore always check and adhere to the manufacturer’s rating for LED dimming.

Advantages and disadvantages of mains dimming

Advantages:

i) Easy to install – as they don’t require additional wiring.

Disadvantages:

i) Compatibility - not all mains dimmers are compatible with all LED drivers, so it’s always best to check with the supplier of the dimmable LED Driver for suitable compatible dimmers.

ii) Capacity – the number of LED light panels that it’s possible to dim in a group is limited by the dimming capacity of the LED dimmer. For example, the maximum load for the Varilight V-PRO 300W dimmer is 300W LED, therefore a maximum of seven 40W LED panels can be dimmed from this dimmer.

iii) Performance – although we generally find that the combination of our dimmable LED panel drivers together with the Varilight V-Pro dimmers offers very smooth dimming performance, this is not always the case with products from other suppliers.

iv) Cost – both mains dimmable drivers and compatible dimmers are more expensive than some alternatives (1-10V dimming)

Low Voltage Dimming

Unlike mains dimming, this method sends an electronic message to the driver, and it is the driver which then dims the lamp using its electronic components. In low-voltage dimming, all the dimmer is doing is telling the drivers what to do. This is different to mains dimming because with mains dimming the dimmer itself reduces the power and sends it through the driver.

As the dimmers in low-voltage dimming do not do the work but instead tell the drivers what to do, they use protocols, which is just an agreed way of transmitting information.

The most common protocols are 1-10V / 0-10V and DALI, but for the purposes of this article we will discuss only 1-10V / 0-10V since those wanting to install DALI will almost certainly be familiar with that system.

0/1-10V dimming drivers have an additional pair of wires, in addition to AC in and DC out – these are the 0/1-10V dimming wires. On our drivers, these wires are colour coded red (+) and black (-). These 0/1-10V dimming wires are connected to a 0/1-10V dimmer. If you were to put a voltmeter across these wires you would find 10V. The dimmer (basically a variable resistor) is used to vary the voltage back to the driver, which the driver then translates into a change in current output to the LED panel. When the current is reduced the light output is increased, whilst when the current is increased the light output is increased.

Please note the comparison between 1-10V dimming and 0-10V dimming shown in the table below:

 

Max. output level (%)

Min. output level (%)

Output level (%) when dimming signal less than 1.00V / 0.57V

Output level (%)when dimming wire is shorted

DC1-10V

100

6.5

Not defined*

Not defined*

DC0-10V

100

10/5.7

10 / 0

0

 * May cause flickering of light

Advantages and disadvantages of Low Voltage (0/1-10V dimming)

Advantages:

Compatibility – we have yet to come across a compatibility issue between any 0/1-10V drivers and 0/1-10V dimmers

Capacity – the current output from 0/1-10V drivers on the dimming wires is typically 0.1mA, and the theoretical capacity of our Aurora AU-DSPLED dimmer is 50mA, meaning that in theory 500 such drivers could be controlled by on dimmer! However, it is recommended that a maximum of 25 drivers are controlled by the 0/1-10V circuit on the Aurora AU-DSPLED.

Performance – we have never heard of any performance issue when using 0/1-10V. The dimming is perfectly smooth.

Cost – both 0/1-10V dimmable drivers and compatible dimmers are less costly than mains dimmable.

Disadvantages:

Installation – since this system requires additional wiring installation costs may be higher than those for other systems (i.e. mains dimmable), and it may not always be easy to conceal this additional wiring (e.g. domestic installation)

Dimmable LED panels