The type of driver your LED has will determine how you can dim it. Every LED comes with either external driver or incorporated driver.
Dimming methods have two parts, which are low-voltage and mains dimming. The latter is used for incorporated drivers LEDs, and it can also be used for dimming LEDs that have compatible external drivers, while low-voltage dimming works only for external drivers.
This type of dimming is common in homes and is the most used by people. They are normally rotary, and they can be found on a wall in place of light switch. They have a dial which can be twisted right or left to increase or reduce the intensity of light and then push in so that the light can be switched off. Mains dimming consumes the electrical signal from the mains in order to work. How is this achieved? The electric current get turned on and off for sometimes in a second.
Less light is delivered in total if the light is on and off at full power compared to when on all the time. Due to the fact that our eyes find it hard to process the quick switching, it is interpreted by the brain as a stable dim light source.
The UK power mains come in a wave and it has a frequency of 50Hz. This implies that this wave is repeated 50 times every second. There are 100 cycles of current per second (50 negative and 50 positive) as the current from the mains switches from positive to negative each circle.
How is mains dimming achieved? This happens as a result of the switching off of the power for a period of time two times in each wave – one for every current cycle. However, this is possible in two ways, which are trailing edge or leading-edge. Phase adaptive, which is the third option is dimmer and is designed to select between trailing-edge and leading-edge. But this selection is based on the one that’s the best.
It’s called leading edge due to the fact that it switches off the signal of the mains right from when the wave began. The leading edge does this for every negative and positive cycle, it turns off and on 100 times each second. It is the cheapest of all, it’s simple and largely available but the problem with it is it causes buzzing at times.
When the wave switches from zero to the peak, this is enough to trigger vibrations in the electronic component due to the movement of electrons surge every time. The stronger the vibration is, the dimmer the lamp will buzz.
This is a sophisticated technology which is designed to fight against budding. Trailing edge works in the way leading edge does by switching off the signal two times in every wave, however, it switches off at the end of every cycle.
The buzzing it causes is not much due to the fact that every time the wave gets switched on, the wave is at the lowest strength of the cycle and grows bigger in a gradual process.
A vibration may not be caused since there is no important difference when switched off when first switched on, and as the current increases in a gradual process. There will be no buzzing without vibration. The technology is expensive to manufacture but it is widely available.
Low Voltage Dimming
This is possible when using external drivers. However, all external drivers may not be compatible with low voltage dimming methods. But you will have the option to choose a low-voltage dimmable driver if you go for LED controlled by an external driver.
The type of driver in use will determine the type of low-voltage dimming available. Modulation method can be used by both constant voltage drivers and constant current drivers. However, it is only constant current drivers that work fine with constant current reduction.
These methods send a message through electronic means to the driver compared to mains dimming, and the driver is responsible for dimming the lamp by using its electronic components.
What the dimmer does is tell the driver what to do in low-voltage dimming. This is not same with mains dimming because mains dimming decreases the power and then send it using the driver.
Since the dimmers in low-voltage dimming tell the drivers what to do rather than do the work, they make use of protocols, which is an agreed means to transmit information. Low-voltage dimmers send information and commands using electrical signals.
Pulse Width Modulation (PWM)
PWM works the same way just like mains dimming. It switches the lamp on and off many times in each second in order to lower the total amount of light produced.
PWM does not have to chop-up the signal of the mains as low-voltage dimming can do the work with its driver. The driver is capable of switching its direct current produced on and off in order to dim.
One interesting benefit of pulse width modulation is colouring rendering does not change at all light levels ranging from the dimmest to the brightest. Strobing is one of the problems, however, the rapid on and off switch is too fast to be noticed, and some people report issues like headache when they are exposed to this type of lighting. The pulsing may likely cause damage to electromagnetic sensitive devices in the laboratory.
However, the problems may not affect most users. People who choose PWM over CCR do this due to the fact that they use constant voltage drivers which are Non-CCR compatible.
Constant Current Reduction
CCR does not switch power on and off as compared to PWM or mains dimming, but it reduces the current delivered to the light, and as the current is reduced it becomes dim, which implies you have a steady power supply rather than wave. This, however, resolves any electromagnetic problem and potential strobing but when the light is dimmed colour rendering is likely going to vary.
CCR and as well PWM are established systems, and there is not much to choose between the two except people have a problem they are trying to prevent.
These are used by dimmer in low-voltage dimming (PWM and CCR) to communicate with the drivers – how the dimming should be.
Protocols have different types but 0-10V and DALI are the most common. They are the language used by dimmers to tell drivers what they should do although they function differently. Ideally, you need to get a DALI that is compatible with the driver if you intend using DALI dimmer and other systems, too.