Flicker Free FAQ’s
Flicker is a risk to any lighting project and in public areas where today’s mobile technology identifies poor quality it is vital to choose premium products. We asked our team of experts in both Lighting control and power for their top FAQ’s.
Question: What is Flicker?
Answer: Flicker in lighting is related to very rapid changes in brightness of a source. To some extent, flicker is in the eye of the beholder – human perception of flicker is variable and some people notice faster frequencies than others. Flicker is a particular concern with LEDs since they have no persistence, any oscillation in the driver current correlates directly to the light output. Hence, PWM (a common method of dimming LEDs) which turns the current on/off at high frequency is a problem if not managed correctly.
Question: Why should I worry about flicker?
Answer: There are a few reasons to be worried about flicker. The most obvious is that it leads to an unpleasant experience – occupiers and visitors may complain of headaches, eyestrain and other ailments. More subtly, flicker is a result of poor system design or components and can easily be designed out with the right expertise. Poor flicker performance is also easily exposed by current smartphone technology and the impact of social media.
Question: How does the control method affect flicker?
Answer: It shouldn’t. If using an appropriate LED driver with integrated control (Phase, 0/1-10V, DALI, DMX etc.), flicker-free operation will be inherent to the specification of the product. Phase (mains) dimmable drivers require particularly good designs to ensure flicker-free operation. Specific attention should be paid when using separate interfaces or controllers – in addition to an LED driver – as a control method, as these components will alter the frequency of the power rail.
Question: Do controllers and interface modules change the LED driver performance on flicker?
Answer: Yes, these additional components operated by switching the power rail on and off at a very rapid rate (PWM). The frequency these modules operate at will determine the flicker rate of the LEDs. These modules can also put undue stress on the LED drivers, as the driver will be in a constant battle to stabilise its output while the dimming module is constantly switching.
Question: Do different installations require different levels of flicker immunity?
Answer: Yes. There are many levels of flicker to consider, from visible and non-visible flicker (and the effects these have on individuals) to stroboscopic effects when lighting around moving objects. There are also particular requirements for flicker performance in conjunction with amateur and professional video.
Question: Flicker and mobile phones
Answer: Recent developments in smartphone imaging software has helped eliminate the dark lines that used to frequently show up in still photos. However, advancement in video capture and processing has
resulted in flicker being much more easily picked up by the latest mobile technologies available. With this technology at everyone’s fingertips and video conferencing becoming a bigger part of our lives, lower quality installations are quickly being exposed.
Question: If I can’t see it, does it exist?
Answer: Possibly. Different people have differing thresholds for observing flicker (the flicker fusion threshold). Studies show that flicker rates which are just above the upper limit, detectable by the
human visual system can still have a sub-conscious effect (eyestrain, headaches, epilepsy etc.). So, due diligence in the design not only ensures professional performance of lighting, but also safe and user friendly operation too.
Take a look at our latest video featuring LTech drivers with T-PWM dimming technology, this is available across the entire range and ensures a smooth flicker-free dimming down to 0.1%.