LED Christmas Lights - Are The Wiring Harnesses Any Better?

[TimR]

I leave mine on the hedge year round.

But they stopped working this year.

Er, right after I'd trimmed the hedge. Not sure that had anything to do with it though.

[DerbyDad03]

You should have left them on so you could see where you were trimming.

Last night I wrapped the utility pole in front of my house with net lights.

A 6' x 4' net wraps neatly around the pole and hooks onto a single vertical line of deck screws. With a 10' step ladder, I can wrap 2 sets, so the pole is lit up to 12' high.

The power/cable/phone companies didn't bother me last year (first year I did it) so we'll see if I hear from anyone this year.

A couple of decades ago they left my basketball hoop on the pole for 3 years. Then one day I came home from work to find it in my driveway along with a letter in my mail box telling me that it wasn't allowed.

[Mark Lloyd]

[snip]

The have to be. A LED maintains a voltage of about 2 or 3 volts. Dropping 120V to this wastes too much power. They use about 25 to 35 LEDs in series.

I lose 1 or 2 (rope lights) every year. Usually it's a series (about 1.5 feet) failure.

BTW, I've already had one series failure this year (after putting them in the yard). I made a loop of the bad part and at night you can't tell anything's wrong.

[Mark Lloyd]

[snip]

They are in series of about 30. Longer strings have multiple series in parallel.

A diode maintains a low voltage across itself (with forward polarity, which an LED needs to light) or at most a few volts. The circuit needs some means of limiting current to prevent the LEDs from destroying themselves. This is usually a resistor. It wastes a lot more current dropping 120V to 3V (single LED) than dropping it to 90V (LED series).

You CAN put LEDs in parallel (if they have the same forward voltage), but that doesn't solve the wasted power problem.

BTW, I do have a couple of light sets that use LEDs in parallel. This is a solar-powered set that uses 20 LEDs and a single LiFePO battery (3.2V) not 120V.

[Mark Lloyd]

[snip]

I have that too. Raccoons come at night, so I put out cat food in the morning so the cats have a better chance. Recently, I don't see any raccoons but plenty of possums. At least they don't mess up the water as much.

AFAIK, I haven't had any critter-related problems with the Christmas lights. I have heard of someone who had a problem with fire ants piling dirt around the lights, tripping a GFCI.

[Mark Lloyd]

[snip]

LED current is commonly 30mA, although there are bright LEDs that need more.

It isn't so much constant current as constant VOLTAGE. A diode is a voltage regulator. It will conduct enough current to bring its supply down to its threshold voltage (usually no more than about 3V). With a directly connected 120V supply, it tries to conduct infinite current (to bring 120V down to 3V) and destroy itself. It needs a resistor so that when it's conducting 30mA, the supply is brought down to 3V (117V across the resistor).

A string of 30 of those LEDs will require 90V to light. The resistor has to waste 9mW (30V * 30mA). Putting the LEDs in parallel would require wasting 105.3W (117V * 30mA * 30 LEDs). A big difference.

Most of the LED light strings I have are one of:

25 lights - single series or 25 50 lights - 2 series of 25 60 lights - 2 series of 30 70 lights - 2 series of 35 100 lights - 4 series of 25

[Mark Lloyd]

[snip]

I find that to be true. CFLs and LEDs do a poor job of imitating the dirty yellow called warm white. They are NOT the same color as incandescents. Get green and red. They're Christmas colors, and the colors are much better than with incandescents. Blue and real white (called cool write) are good too.

[clare]

They are wired similar to the old series string mini-lights - but when a LED fails id very seldom fails "open" - so the lights stay on unless you have a bad connection. My experience with mini-light strings (and cheap LED stings) is it is USUALLY a wire connection problem rather than a light problem that takes out a section.