> I am certainly not an expert on such things, but I've also been of the
> understanding that one way to "dim" LEDs is to pulse them - turn the
> electricity on an off - the more "on", the brighter they appear, the
> more "off" the dimmer they are.
You are correct, that is another way to dim them - turn them on and off very
rapidly and let the eye do the "total light from the
device" integration over time.
In its simplest form, it is all about heat. When the LED conducts, it heats up.
If the junction gets too hot, it will destroy
itself. But it will tolerate reasonably high currents for very short periods of
time - in the milliseconds range. At these very
high levels of current, it puts out lots of light. But you must turn it off to
allow it to cool down - or buy another LED. It
often taking longer to cool down than it did to heat up, but again it can be in
the milliseconds range and can be helped with heat
sinks, etc.
An interesting side effect of this is the way the eye behaves as the
integration device. It reacts more to the high on levels than
is does to the low off levels so the perceived brightness is more than if you
just did the simple math of (on-time *
brightness-when-its-on) divided by total-looking-at-it time.
Or you can think of the pulsing as a crude current limiting device. Pulse X
amount of current for Y amount of time, and then zero
current for Z amount of time, the "average" current is X current divided by (Y
time + Z time). As long as the X current and Y time
values are not enough to cook the junction, everything is ok and it seems to be
brighter than if you just pushed the average value
of current thru the junction in the first place.
Many of the "experimenter flashlight circuits" use this principal to get very
bright flashlights with really long run times from
small batteries - giving the perception that more light energy is being
extracted from the battery than the energy capacity of the
battery would indicate possible.
>Or I may be completely wrong, and that doesn't solve the problem of
>dimming the LEDs based on a wall switch mounted dimmer...
You are correct, a regular wall mounted dimmer will have no reliable effect on
the LED strips.
Arvid
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