With LED lighting becoming the norm for many lighting situations in houses of worship, and with cheap LED lighting still luring customers in with either low prices or claims of many hours of service from the LEDs,
I thought it might be useful to talk a little about how LED lighting works. Because, it's not as simple as you might think.
If all you ever wanted is for an LED light fixture to be on at 100 percent light output, LED lighting would indeed be a straight-forward item (from the electrical perspective) to produce.
However, most churches are interested in lighting that can be dimmed, and that's where the complexity and cost of LED fixtures kicks in.
(Note that the following is not to be a detail thesis on LED electronicsthe concepts have been simplified for the purpose of the article.)
Unlike regular incandescent light sources, LEDs do not dim when you lower the amount of electricity going to them.
LEDs (or Light Emitting Diodes) actually work like this: the diode does not allow electricity to pass through it at all until a certain voltage is reached (the threshold point); once this threshold is exceeded, electricity passes through freely and the diode emits 100 percent of its potential light output.
So, it's either on, or it's off. There is no in-between as with an incandescent light source.
So, how do dimming LED fixtures dim? Excellent question I'm glad you asked!
An LED light source has electronics in it that, based on a control signal coming into the fixture, turns the light on and off quickly. I.e., it blinks the light.
If the LED is on only 50 percent of the time, and it's blinking very fast, then it appears to be at 50 percent of its full brightness.
It's a little like watching a movie there's 24 still photographs being projected onto the screen each second, but that happens fast enough that our brains see it as smooth, fluid movement, not still images.
There are LEDs light bulbs that don't take a control signal, and instead dim based on the voltage being sent to the fixture. What's happening here is that LEDs actually only need about 1 volt of power to emit light; and the control electronics probably only need 3 volts or less to operate.
Our normal electrical service in the US is 115-120 volts, and 220 volts in other parts of the world. Therefore, it's possible to create electronics inside the light that can operate the LED until the voltage coming in drops below what the electronics need to operate once that happens, the light will simply go out.
And these same electronics are measuring the line voltage, and using that measurement as the control signalif the line voltage is at 60 volts, that's 50 percent of 120 volts, so it sets the LED to blink at a rate that would appear to be 50 percent intensity. Thus why many LED light bulbs that you might use in your house only dim to a certain point, and then suddenly go completely out.
I've seen some theatrical LED fixtures (Chauvet has one) that, while accepting a DMX control signal, will also dim based purely on typical line voltage dimming. I expect that these fixtures have some sort of electricity storage system built in (kind of like a rechargeable battery backup) that operates the electronics, and allows the fixture to dim smoothly all the way to 0.
And, this is why cheap LED fixtures flicker on videothe electronics aren't sophisticated enough to blink the LEDs at a rate that looks good on video. The slower the blink rate, the more flicker that a video camera sees.
This is also why, despite the claim that a fixtures LEDs will last for 50,000 hours, cheap LED fixtures die long before the 50,000 hour point is reached.
I expect if you did some forensic testing on a dead LED fixture, you'd find that all the LEDs are perfectly fine. The cheap electronics that run them, however, are dead.
What you're paying for in the expensive fixtures is higher-power LED emitters, better optics, sophisticated electronics that keep the light from flickering on video, and high quality electronics and heat sinks (a part that transfers heat from the device to the air outside the fixture) to help ensure that the electronics last as long as the LED emitters.