Light Box Electronics 101: Ballasts
Q. Do I want “Magnetic” or “Electornic” ballasts in my light box?
A. Almost all light boxes designed for backlit graphics display, use fluorescent lamps because of their superior diffusion quality and economy of purchase and operation. These fluorescent lamps are driven by one or more “ballasts”, which convert the electricity from a normal wall outlet down to the right type and quantity of power for use by the lamps in your lightbox. In this way they are similar to a “power pack” you would find on the cord for a laptop computer or other device. There are two types of ballasts used in backlit light boxes: magnetic and electronic. While the visual result may appear the same to the passer-by, there are significant differences between the two:
ECONOMY. Magnetic ballasts have been in production for three quarters of a century and have reached a very efficient price point. Magnetic ballasts are often found in economy-grade light box models such as Blue River Digital’s EasyLyte II. This helps to keep the overall product cost down. On the flip-side, magnetic ballasts tend to cost more to operate, in terms of power consumption, especially at start-up. Many of us remember as kids being told not to turn the fluorescent classroom lights off, because it takes more electricity to turn them back on, than to leave them on.
NOISE. If you’ve ever associated fluorescent lights with a “hum” sound, then this was a magnetic ballast installation. Electronic ballasts yield no detectable hum. The magnetic hum does not necessarily indicate any flaw or abnormality; it’s simply the nature of a fully magnetic device.
FLICKER. Perhaps the most compelling case for electronic ballasts is the reduced flicker. Magnetic ballasts produce a notorious flicker, especially when cold and/or the lamps are near failing point.
STARTUP TIME. Magnetic ballasts require a warm-up period prior to full efficiency, which results in less than bright and solid lighting, until standard operating temperature is reached. Again, the colder the environment, the more noticeable is the startup time.
LAMP LIFE. I bet you can’t guess which type of ballast is more efficient at driving fluorescent tubes at their target brightness without overdriving them? If you guessed “Magnetic”, you were wrong!
FIRE SAFETY. While no electric component is immune from overheating, magnetic ballasts by their design are likely to wear out and fail, possibly causing overheating, over a much shorter cycle than electronic.
It’s pretty clear which ballast type has the better track record of performance, but it just goes to show how powerful low price can be, in keeping an old product in the marketplace. For most modern retail usages, clearly magnetic ballasts are not acceptable; except of course if you’re going for that “retro” look in your store space.