Christmas-tree decoration bulbs - How do they do that?

[broadgage]

Originally Posted by IanBland

Is it just me, or are blue LEDs starting to look a bit dated? Are they the fake woodgrain of our times?

Yes, I found them attractive when still new and relatively rare, but now that they are everywhere I don't much like them.

[TonyDuell]

I find it mildly ironic that the traditional Christmas colours are red and green (think of holly, for example). Red and green LEDs made reasonable Christmas lights. But as soon as blue LEDs became affordable everyone jumped on the bandwagon and made blue Christmas lights for no particular reason.

Anyway, I celebrate Newtonsday

On the subject of blue LEDs, I can remember when the Maplin shop in Bristol got their first one in stock back in about 1990. I bought it (cost me a tenner or so). I was at Bristol University at the time, I stuck it in a breadboard with a suitable series resistor and powered it off a bench supply. Half the physics departement wandered into the lab to see it...

[Radio Wrangler]

Red and green make people think of warmth and Spring, blue makes them shiver. Red and green are much more cheering at Christmas. The blue fad will pass.

I remember getting a sample of an 1800 mCd green LED. Brightest thing anyone in the lab had seen. You could aim it across the building and see twinkles off the light fittings in the distance. an LED you could see by! Caused a similar stir.

David

[IanBland]

I've just purchased a bunch of orange LEDs which are very jolly and that kind of colour approximates the candles that used to light Christmas before we started with the blue thing. Each, according to the spec, approximates the light from six candles.

But somehow Christmas just isn't the same without the ancient ritual of Dad trying to figure out which bulb has blown in a string. It has always appeared to me that the old incandescent lamps were designed to blow randomly in storage. Hence the singing of the carol "They were working fine when we put them away last year".

[The Philpott]

That is exactly it Ian- an Xmas tradition we didn't even realise existed until LED's made it seem outdated.

The most fascinating filament ones to me were the bimetal strip ones that did a very slow flash- the voltage had to be matched to the average number of bulbs that were lit at any one time, as each bulb heated and cooled independently! Try getting a set of them now..

[paulsherwin]

The currently fashionable LED colour seems to be warm white. These look very like conventional clear bulbs, but have a much longer life.

[The Philpott]

Warm white 2700Kelvin has certainly been achieved and the CRI is quite good.
Now looking at 80 to 95 lumens per watt with proper control gear. The coloured 'pub style' GLS 20 string i have (outdoor use) actually have painted glass envelopes but the LEDS inside are most definitely white. Reluctantly gave in to modern tech on this one as the consumption went from 500w to 30w.- and they still look old at casual glance.

[broadgage]

As we all know, attempting to find the failed lamp in a series string can be most irritating, here are some ways to make it easier.

Most lighting sets of 20 lamps or more have all the lamps in series along one wire, with the second wire being continuous from the last lamp back to the plug, and the two wires twisted together.
Connect the long continuous wire to mains neutral, with the mains live being connected to the shorter wire that goes to the first lamp.

A failed lamp or other open circuit such as a defective connection is then easily located with a "voltstick" or similar, starting from the live end.
If however the mains live has been connected to the long wire, then a voltstick will probably light at every point along the string due to the proximity of this live wire.

Shorter strings of 12 lamps are often wired in a ring with only a single wire. In that case it is helpful to always connect the same end of the ring to mains live, and to mark the first lampholder at the live end.
A short piece of red heatshrink over the wire near the first lamp holder does this neatly.
Any failure is then quickly found with a voltstick, knowing at which end to start.
Removing each lamp and testing it with a small battery does not always work since it wont reveal a lamp that is sound but that fails to make contact in the bulb holder.

Very long sets of lights may be assembled by connecting numerous short strings end to end, with an additional mains live and mains neutral running the length of the string, and connected as needed.
If doing this, it is helpful to know where one series string ends and the next begins.
I once made up a string of 144 lamps consisting of 12 series groups each of 12 lamps. The first lamp in each set of 12 was always white, with the other 11 lamps being a random selection of all other colours.
Knowing where one group of 12 ended and another began helped to find the faults.

[The Philpott]

The 'tails' on push-in lamps are often dull or slightly corroded, even when new out of the packet. I can only conclude that the plastic reacts with the copper. This can set up a failure of the whole set to light.

I have a set of the clear 'multi pointed star' diffusers that were popular at some point; how they passed certification i will never know, they were loose on the lamps and if you trod on one in bare feet you'd end up in hospital. No joke here, i think they could take out a racing bicycle tyre.

[IanBland]

Broadgage-

This presupposes the existence of a voltstick, which was tantamount to science fiction in the heyday of the filament Christmas lamp. I believe the preferred method was to replace each lamp one at a time with a new (believed sound) lamp until the string lit up. If this failed due to two or more failures, the father would then start holding the lamps up to a bright light (e.g. 60W incandescent or the Sun) in the hope of seeing the failed filament.

ThePhilpott- IIRC all ours had little "snowflake" shaped shade/reflectors which were also quite painful to tread on. We later upgraded, in the late 70s, to some lantern shaped efforts.

[broadgage]

Yes, back in the day voltsticks were either unknown or at least not generally available.
They are however most useful these days for finding faults in series strings of lamps.

Another old technique for finding the open circuit was to connect one end only of the series string to mains live, with the other end not connected to anything.
Then make up a test lead consisting of a 15 watt mains voltage lamp with one side of the lamp connected to mains neutral and the other side of the lamp to a wander lead with a bare end.

Remove a lamp near the mid point of the series string and poke the wander lead into the lamp socket. If the circuit be continuous from mains live to the mid point, then the lamps will light, dimly.
If not try again half way along the defective portion.
This method is not entirely safe and great care should be taken. An RCD or an isolating transformer would be a wise precaution, though no one bothered in the old days.

[Herald1360]

I just used to go down the string removing each bulb in turn and prodding the holder with a neon screwdriver.

Not infrequently when the last bulb reached so far was screwed back in, it all lit up.

[dseymo1]

Well, I suppose the enerprising householder could wind a coil on a nail and connect it to his record player, monitoring hum levels to achieve much the same as a Voltstick.

The 'snowflake' LED sets still pose a challenge when looking for faults, with their complex series-parallel arrangement!

[McMurdo]

volt sticks go back quite a way, they used them in the mines in the 1970's. Someone gave me one as a boy and I fascinated mother by fixing the lights this way in record time.

[IanBland]

I don't think I saw a volt stick until 1990, quite possibly later than that. I'm trying to remember when I first bought one. I just remember the realisation of how amazingly useful they are, both for fault finding and as a "first line safety measure".

[cheerfulcharlie]

Then there was the now largely forgotten fibre optic trees. Very reliable as only one MR16 bulb to worry about, in fact the most unreliable thing about it
was the relatively heavy and unwieldy transformer power supply supplied to drive the lamp,fan and colour wheel- the connections used to get damaged as it got chucked about behind the sofa and put back in the loft etc

[broadgage]

Fibre optic Christmas trees are still popular, one large retailer was selling them last Christmas.
Some types still use a halogen reflector lamp, similar to an MR16 but smaller. Unfortunatly there has been a decline in the lamp wattage often down to 5 watts, in order to cheapen the transformer and eliminate the fan.
The results therefore tend to be disappointing except in complete darkness.

Updated versions tend to use small LEDs often of inadequate light output.

[Hunts smoothing bomb]

The smaller halogen reflector lamp often used here is known as the MR11

In the case of these 5 watt lamps being fitted in a bid to cut down transformer costs I would fit a 5 watt MR16 or MR11 12v warm white LED, that will produce around 400lm!

Cheers

[The Philpott]

Things can get ugly with fibre optic trees if you have more than one- I had two- one with a 12V AC power cube and the other 6V DC.

[Herald1360]

Magic smoke released?