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What invisible flicker do different types of light bulbs have?
- Kaibeezy 6y agoI was looking all over for a concise explanation of the different elements of flicker. Yes, to win an argument, but really to get agreement to use incandescent bulbs in the locations where I spend a lot of time. There's so much useless, imprecise, misleading and otherwise unusable information out there, it was getting discouraging. And then this person nailed it: Incandescent lamps have a lot of thermal inertia. Because they are hot metal, the filament can't heat up and cool down 120 times per second, so they don't flicker. Flourescent lamps work by a glowing gas (Mercury) that gets phosphor glowing on the inside of the tube. White phosphor is pretty fast, so a cheap flourescent can flicker. Radar and sonar displays used to use a very slow green phosphor that would not flicker, but who wants a green light bulb? LEDs are super fast. If you drive them with DC, they will not flicker. But, LEDs use very low voltage (around 1 volt) and converting 12 or 120 volts to a small DC using resistors or transistor in old-fashioned "linear" regulation wastes most of the power. So, folks usually pulse width modulate (PWM) LEDs. This turns them on and off at a very fast rate. It wastes very little power and allows you to vary the brightness by changing the % of the time it is on. If the on/off frequency is high enough, you can't see any flicker. One issue is that if you move your head quickly, the LED will look like a dotted line. Modern car tail lights have this problem. This explains why I'm OK with my LED desk lamp... it's 12V DC. It explains why LEDs are miserable with dimmers. It explains why incandescent is so soothing. Thank you David Hoatson.