LED Lights Power Draw Measured

[Carlos Alvarez]

There is one more benefit that LED has over florescent lights. Florescent lights flash like a strobe light. They flash at about 120 Hz (every time the sine wave crosses "zero"). Your eyes see it, but your brain cannot process the info that fast (about 100 Hz is the limit) so they look like they are on all the time. This strobe effect although not noticeable causes eye fatigue and with some people headaches. LED's are a DC device, so they don't flash and are better for your eyes.

Not quite accurate. LEDs in these fixtures are DC powered from an AC source. That means they still get pulsed. See the waveform below:

PIC.88.JPG

If the power supply has lots of filtering, it can become flat, clean, non-pulsed DC. But most cheap power supplies still pass some of the pulse along, and the LEDs flash also. In fact an LED is MUCH more sensitive to this and will flicker much more. Flourescent and incandescent lights don't respond instantly; there is some power down/power up delay. LEDs are really instant. They also have a very tight voltage threshold, so while other lights may just be dim with low voltage, an LED will just shut down.

And the fluorescent sensitivity thing has been mostly debunked anyway.

Here's the first hit on a quick search:

Why Do LEDs Flicker?
When a new source comes to market, the issue of flicker bubbles to the surface. However, LEDs may oscillate in light output even more than incandescent or fluorescent lamps did, says PNNL’s Miller. Unlike HID or fluorescent, solid-state lighting is a direct current (DC) device, meaning that as long as constant current is supplied, the LED will illuminate without flicker, Benya says.
In the case of a simple LED circuit in which no constant current regulation is implemented vis-à-vis a driver, the LED’s brightness will vary in phase with the cycle of the alternating current. When a driver exists, it presents both a source and a solution. Rectifying the AC to DC conversion causes a ripple in the voltage and current output from the driver to the LED. This ripple typically occurs at twice the frequency of the incoming line voltage—120 hertz in the U.S. The LED output then correlates with the output waveform of the driver.
Dimming is the other primary cause of flicker. Conventional dimmers, such as TRIAC (meaning an electronic component that can conduct current in either direction) dimmers, modulate the current by extending the off time in the on–off cycle, reducing light output. Pulse width modulation (PWM) dims LEDs by turning them on and off at frequencies that ideally exceed 200 hertz. However, Benya says, “if you do PWM at a low enough frequency, such as our normal power line frequency, then once again, we’ve introduced a very high percentage of flicker.”

[Greg R Bradley]

There is one more benefit that LED has over florescent lights. Florescent lights flash like a strobe light. They flash at about 120 Hz (every time the sine wave crosses "zero"). Your eyes see it, but your brain cannot process the info that fast (about 100 Hz is the limit) so they look like they are on all the time. This strobe effect although not noticeable causes eye fatigue and with some people headaches. LED's are a DC device, so they don't flash and are better for your eyes.

Fluorescents pulsing at 60Hz, so on/off 120 times a second, is only for the magnetic ballasts used in the original T-12 fixtures. Obsolete for decades now. Electronic ballast cycle at a typical rate of 20,000 Hz. LED have a BIG problem with flashing, more than modern fluorescents.
Both are affected by the quality of the fixture and there is a lot a variation in all of them, as well as most lighting powered by 60Hz AC power.

[Bob Bouis]

The t8 LED tubes tend to have poor quality drivers, too.

[Carlos Alvarez]

Not to beat you up on it Daniel, but would you share where you got this misinformation about flicker? It's an honest curiosity. Working in tech, I'm constantly battling tech myths and always wonder how they came to be.