Flicker Checker - Once for Magnetic Ballasts, Now for LED

As a student at the University of Kansas I worked for the EADC - Energy Analysis and Diagnostic Center. This was a fantastic DOE-sponsored program (now called IAC) which employed college students to perform free energy audits of manufacturing plants and commercial office spaces and then provide them a report full of Energy Conservation Opportunities (ECOs.) One of our most common ECOs at that time was: replace existing T12 fluorescent lamps and magnetic ballasts with energy-saving T8 fluorescent lamps and new electronic ballasts. One of the added benefits of this upgrade was the elimination of "flicker." Though imperceptible to some, flicker can be quite problematic for sensitive individuals, causing headaches or even seizures. Flicker happens with the natural cycling of AC power, but with the higher frequency inherent in electronic ballasts, the fluorescent phosphors do not have time to dim, and therefore flicker is eliminated.

We had a handy tool that we could use to verify whether the existing ballasts were magnetic or electronic. It was a top, called a flicker checker. When you spin it under electronic ballasts, you see a series of concentric gray circles like in the first video below.

However, if the existing fixture had magnetic ballasts, the flicker checker displayed choppy squares instead of concentric circles, illustrated in the video below. 

The thing is, this second video wasn't a top spinning under a fluorescent lamp with a magnetic ballast. It was spinning under a dimmed LED fixture! Once again we need to watch out for flicker in our lighting. The great news is that this time almost everyone is armed with their own personal flicker checker! No...maybe not a top. Pull out the camera on your phone and point it at the nearest LED source. If you see a series of bars or stripes on your display, the source is flickering. If not, then you have a high-quality LED with a compatible dimmer and/or driver.

LED source with flicker - note white vertical lines in photo

Magnetically ballasted fluorescent with flicker

Electronically ballasted fluorescent - no flicker

Try it. Let us know what you find!