Buying LED Lights

Bottom line: make sure the LEDs you buy are dimmable FWR bulbs.

What follows is uninformed hearsay because I still have not found an authoritative source that explains these issues sufficiently. I have the usual collection of two or three strands per year picked up randomly. I got a few LEDs a while back, some were good some weren’t.

LEDs have the obvious advantage of low power (4W per strand vs 24W) and longer life, but at about seven times the cost (in 2013). The criteria that I’ve found I should look for in LEDs are the following:

• “Retail” vs “Pro Grade”
• Dimmable
• Full Wave Rectifying (FWR) (non flickering)
• Dome vs Conical (5mm) vs “Classic” (M5/C7) bulbs

One thing I’m sure of, don’t get domed, they act like little blinding flashlights. It’s cool for disco balls, but not so much for Christmas. Conical (chopped off cylinders) work well. They are bright, even, tiny points of light. I prefer the “classic” (M5) look for most uses, but the conical work well for outside tree branches.

Retail vs “Pro”: This seems to come down largely to marketing, but “Pro” is more often FWR (less flickering), maybe slightly thicker wire insulation, and smoother dimming.

Dimmability: LEDs are generally bad at dimming. Unlike the smooth fade of incandescents, LEDs must be programmed to have discrete steps of brightness, and then they just turn off. Some do not dim at all. Make sure you buy dimmable FWR LEDs.

Bulb sizes: M3, M5, C7, C9 , etc. "M" is skinny and long, "C" is old fashioned candle-like bulbs. Here’s a good video from ledholidaylighting.com that explains the different bulb shapes youtube.com/watch?v=9_gXbv6W5lc

As for poorly dimming “retail” lights I’ve read about people trying to add shunts and terminators to their strands to help with spastic dimming characteristics. I have yet to see a real electrical engineer comment on this so caveat emptor, it all seems trial and error. The theory behind shunts is that an LED strand is so sensitive to power fluctuation that adding something that draws more current will smooth out the power and make the whole strand take on the dimming characteristics of the extra bulb. I have not experimented with this, and people who seem to know more are calling BS on this. You can't force a non-dimming LED to dim since it's electronic, but I guess you can prevent a "dimmable" LED from flashing on and off randomly as you try to dim it. I may experiment after this season. I can definitely see the difference in dimming between my newer and old strands though.

Glossary:

LED: Light Emitting Diode. A small electronic light source that can produce any color directly without colored glass. Being electronic they require more precise current to behave well.

FWR: Full Wave Rectifying LED lights. These don’t have the “corner of the eye” flickering that cheaper LED’s have. Is the rectifier the bulge in newer light strands? Not to be confused with “full spectrum” lights.

Rectifier: A rectifier converts AC current to DC so power is applied only on half of the 60Hz AC wave so the diode lights up 60 times a second. This is what caused flicker on older LEDs. Full wave rectifiers provide power all the time (both waves).

Shunt: An extra thing on the light strand drawing more power, hopefully helping the lights dim better. Fiction? I have read about people adding extra C6 incandescent bulbs and even air fresheners.

Terminator: a resistor at the end of your strand. This can help with lower quality “retail” strands.  Apparently LOR has upgraded their hardware to make this unnecessary. More here: crazylightlady.us/TerminatorsHow-To.html