Christmas mini lights (filament/incandescent, not LED) - question about voltages - Page 1
Forum section: electronics / general

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 28, 2023, 06:11:22 pm
content: I have some Christmas mini lights (filament), the type on a wire loop that plug directly into the mains with no transformer or control box with assorted settings. They're either on or they're off. The bulbs are the push-in type that look like this:https://www.thechristmasshop.co.uk/p/coloured-bulbs-for-140-konstsmide-lightsBecause I'm in the UK the mains voltage is 240 volts - as the string of lights plugs straight into the mains that of course doesn't mean the bulbs are each capable of handling 240 volts. I always thought that they were usually rated at around 9 volts (but now see from looking online that some even start at 1.5 volts). Because they are wired in series on a string that means that the voltage is 'evened out' between the bulbs (there's 100 on a string). Therefore in series that's 100 mini lights and a mains voltage of 240, meaning each bulb is rated at 2.4 volts? Is that correct?I also note that if I bend out the wires on the base I can test them individually with a small 9 volt PP3 battery and the light seems as bright as it is when they are on the string powered from the mains. However if they really are only 2.4 volts each then I need to be careful to only very quickly check any suspect ones at 9 volts .......In addition to the above does anyone know if there's a list anywhere of the different sizes and voltages of filament mini lights? I've tried Googling but to no avail. I know that some have a slightly wider base for example and they don't plug into some light strings with push-in holders that are designed for a slightly narrower base, other have a slightly different shaped base. It would be useful to be able to look at a table when ordering spare bulbs to ensure that the right size and voltage is purchased. Unfortunately these mini lights of different sizes don't seem to have any markings, I guess there's no industry standards then?

author: mendip_discovery
author_rank: Super Contributor
timestamp: October 28, 2023, 06:32:28 pm
content: Why bother with them. They regularly use different/proprietary bulbs so it's always been a pain to use them. They also had a nasty habbit of catching trees on fire etc.This is one of those times were it's really nice to have LED.

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 28, 2023, 06:38:45 pm
content: I really hate LED Christmas bulbs - the colours are usually slightly off/unnatural and the light is overly bright and harsh. Blue light in particular is the worst.Filament bulbs are a lot better (for me at least) as they give off a far nicer, softer glow.But if you prefer LED bulbs then that's fine, we all have different preferences.

author: mendip_discovery
author_rank: Super Contributor
timestamp: October 28, 2023, 06:46:25 pm
content: I am quite lucky to find a set that is a lot like the old lights so not that far off. I will admit some of the lights I see now have horrible glare so I find them distracting. Don't get me started on all those people with the blue lights on outdoor trees/hedges set to flash blue light drives me potty.

author: Gyro
author_rank: Super Contributor
timestamp: October 28, 2023, 06:50:21 pm
content: There are a few different types base moldings... and voltages, 100 is a long string, most are / were 24, 36 etc. The voltages aren't necessarily matched to the bases - I remember for years the family had strings with a mixture of dim and bright bulbs. The reason that you have similar brightness on battery is that the PP3 battery probably has limited current availability. Either that or there is more than one string in parallel - but in that case, there would be more wires than a simple loop.Flilament lamp strings are (were) cheap disposable items, supplied with a few spare bulbs (including a couple of spare white topped fuse bulbs). By the time one bulb blows, all the others have reached the far end of the bathtub curve.I agree that traditional filament lamp strings look better (well, more traditional) but theyt are really at EOL from the safety perspective, cheap single insulated wire and no strain relief in the holders, a definite young kid and pet risk, they wouldn't pass a safety inspection these days. There are at least plenty of LED sets that default to power up in steady illumination rather than brain-frying psychedelic mode.

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2023, 06:57:11 pm
content: 'Back in the day', I had to maintain several antique strings of Osram Christmas lights on a yearly basis, and getting spares was always a problem. Key parameters to match are no. of lights in the string and bulb wattage. As you are using push-in bulbs, if you are having difficulty finding ones that fit, keep the bases off any blown bulbs as they can be transplanted to new bulbs.One absolutely key detail you must be certain of is whether or not the set uses self-shorting bulbs. Self-shorting bulbs have a wrap of thin magnet wire internally round the two leads supporting the filament (which can be seen if you look closely). If the filament goes open, the mains voltage breaks down the magnet wire insulation, spot-welding it to the leads and shorting out the bulb so the rest of the lights stay on, albeit at a fractionally higher voltage. This decreases the life of the other bulbs so its critical to stay on top of checking for and replacing dead bulbs for the duration of your display. Self-shorting bulb sets *MUST* have a fuse bulb (a special bulb without the shorting wire and with enough lead separation that it wont arc over when it fails, identified by a white paint dipped tip) fitted in one socket (usually the one next to the supply lead), or an appropriately rated mains fuse (and no, even a 3A BS1362 fuse in the plug isn't sufficient protection), to prevent them becoming a fire risk.

author: mendip_discovery
author_rank: Super Contributor
timestamp: October 28, 2023, 06:58:28 pm
content: Would be nice to go full Matt Parker on the LED tree lighting.

author: Gyro
author_rank: Super Contributor
timestamp: October 28, 2023, 07:05:25 pm
content: Quote from: Ian.M on October 28, 2023, 06:57:11 pmI believe they use Aluminium wire, relying on oxide breakdown to make the short. Of course there's no Oxygen in the bulb toprevent it fromalow it to re-forming. Yes, the fuse bulb is vital, a clear bulb with a white painted top (in the UK anyway).

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2023, 08:04:05 pm
content: Thanks for the correction - that makes more sense than magnet wire.

author: wraper
author_rank: Unknown
timestamp: October 28, 2023, 08:10:34 pm
content: Quote from: SolderSucker on October 28, 2023, 06:38:45 pmJust buy decent looking LED lights. For similar cheap price you can get them both with nice warm colors or totally awful. Those incandescent lights are an absolute rubbish. Not only they are not electrically safe, they are very unreliable. Going for a week with no failures is very unlikely.

author: IanB
author_rank: Super Contributor
timestamp: October 28, 2023, 08:16:28 pm
content: Quote from: wraper on October 28, 2023, 08:10:34 pmI've done for fairy lights the same as I have done for other incandescent lamps. Run them on a dimmer at reduced brightness. Then they run for years without failure. Most of the time full brightness is too much for me, subdued lighting is much more pleasant. So it's a win-win situation.

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 28, 2023, 08:22:13 pm
content: Quote from: wraper on October 28, 2023, 08:10:34 pmI've used filament lights for some time but after a recent break (while I tried LED lights) I went back to them. Only ever had a problem with bulbs failing and then not that often. Bulbs these days also have a built-in shunt, so when one bulb dies it doesn't take the whole string with it and the dead bulb is easy it identify. They are definitely not "absolute rubbish".I've tried all kinds of LED bulbs, both cheap and expensive, andnonehave appealed - their harsh and incorrect colours are not to my taste.

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 28, 2023, 08:23:05 pm
content: Quote from: IanB on October 28, 2023, 08:16:28 pmI've never tried a dimmer with the filamant lights - is there any particular type that you would recommend?

author: IanB
author_rank: Super Contributor
timestamp: October 28, 2023, 08:27:11 pm
content: Quote from: SolderSucker on October 28, 2023, 08:23:05 pmAny regular lamp dimmer will do it. In the USA there are "table lamp dimmers", which have a socket you can plug a table lamp (or fairy lights) into. I have not looked to see if you can buy such a thing in the UK, but I would guess they are available somewhere.

author: Zero999
author_rank: Super Contributor
timestamp: October 28, 2023, 09:33:31 pm
content: Quote from: Gyro on October 28, 2023, 07:05:25 pmI thought they used a low pressure gas, with a low breakdown voltage, which would drop to a normal filament lamp, once the arc had struck.

author: TimFox
author_rank: Super Contributor
timestamp: October 28, 2023, 09:39:15 pm
content: For some reason, the normal LED strings sold here for Christmas lighting are much brighter than my wife and I like.

author: Gyro
author_rank: Super Contributor
timestamp: October 28, 2023, 10:37:20 pm
content: A totally off the wall suggestion, which might lookreallyugly!...https://www.ebay.co.uk/itm/111023835999

author: AndyBeez
author_rank: Frequent Contributor
timestamp: October 28, 2023, 11:36:10 pm
content: We have been driving our retro incandescent Xmas lights with a dimmer for many seasons. Running at 80% has little impact on visual brightness but, reduces heating and extends the lifespan of the strings. Also, a dimmer provides a soft start, treating the ageing filaments with care. I have zero idea if spare bulbs even exist. One string is so retro, the bulbs are LES fitting.Image. I cannot recommend this dimmer as I do not own one but, such plugin devices exist for UK sockets. This one is quoted at 300W. Be sure to downrate the fuse in your festive light string's plug to 3 Amps. I should add that a dimmer is not ever compatible with mini LED transformers - they are buck converters and will likely buzz very loudly if dimmed.

author: Brumby
author_rank: Unknown
timestamp: October 28, 2023, 11:54:10 pm
content: My only foray into Christmas tree light fun and games originated in the days of filament only globes wired in series for plugging directly into the mains supply.The first set I remember had a string of globes rated for 17V. They had a screw base and, from memory, were about 5cm or so long (it's been a while). These were in the days of, if one globe failed, the whole string went dark. Chasing down the faulty globe was THE Christmas ritual nobody liked (I didn't buy my first multimeter until some years later).In the early days, flashing lights consisted of one "special" globe that, when fitted, would make the whole string flash. Yes ... bang - bang. All on, all off. It was quite dramatic - and in those days, a cool feature.We then got an "aluminium" Christmas tree - tripod base, wooden pole trunk with angled holes and steel rod branches with fringe cut "aluminium" (more like a metallised plastic sheet, I reckon) spiral wrapped around them for the leaves. It was very pretty, albeit completely inorganic, but not the place to run a string of lights that came with a 240V risk, so the old lights were draped over a timber slat divider, well away from danger.Anyway, I had an idea.I purchased a set of 20 lights - again full mains operation - and confirmed a series connection of all the globes, which indicated they operated at 12V.First step was to cut off the mains plug and toss it. I then ran a length of 2 conductor cable down the string and joined each conductor alternately to the light string, resulting in 20 globes wired in parallel. I now had a 12V set. Connect this up to a 12V transformer and the electrocution risk was gone. Care was taken to prevent any wayward "leaves" being a problem and over the years, there never was one - even though I did a spiral wrap with some thin tinsel to keep the wiring together and camouflaged.This configuration had another benefit.The bang-bang flashing behaviour could now be tamed. By replacing a normal globe with a flashing globe, only that one globe would flash. With my new setup, I had 3 flashing globes, so I was able to set up the string so that most of the globes were on full time and only 3 globes were flashing - and they were flashing at different rates, so that after a minute of operation, they were so out of step, the result was random twinkling. This was so much more appealing.A year or two later, I did a similar thing with a string of 40, wiring them as 20 lots of two 6V globes in series, again working from 12V.

author: IanB
author_rank: Super Contributor
timestamp: October 29, 2023, 12:06:29 am
content: Quote from: Brumby on October 28, 2023, 11:54:10 pmI seem to recall from my childhood that some of the strings had special sockets that shorted out if you removed the bulb. So finding a faulty bulb just involved removing each bulb in turn until the string came back on. Also, if you had a faulty bulb on Christmas Day with no spares available, you could just remove the faulty bulb until you could obtain a replacement.There were also, of course, the bulbs that failed short internally as noted above, so all you had to do was to look for the dead bulb.

author: tom66
author_rank: Super Contributor
timestamp: October 29, 2023, 12:11:41 am
content: If you find LED Christmas lights too strong for your taste, a bit of permanent marker (in the colour you want) can turn white lights of your choice into more pleasant alternative colours. And it usually lasts the season because the LEDs don't get too warm. It can also tweak the colour of existing coloured lamps though you've got less to work with in brightness terms.

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 12:11:51 am
content: Instead of a dimmer chuck a suitable capacitor in series with lamps.One of my earliest shocks was thanks to christmas tree lights,its only 12 volts so perfectly safe to play with,nope.

author: IanB
author_rank: Super Contributor
timestamp: October 29, 2023, 12:36:35 am
content: Quote from: themadhippy on October 29, 2023, 12:11:51 amThis doesn't make sense. A dimmer is a robust, consumer safety-tested, insulated device. A capacitor is a bare metal component with exposed leads. The one is not like the other.

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 02:32:33 am
content: Hopefully people around here are aware not to leave a cap thats connected to the mains flapping around in the breeze,just as there aware not to use a dimmer that's not in a suitable enclosure

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 29, 2023, 03:53:20 am
content: Or use a diode, trivial to seal up in heat shrink.

author: Zbyszek
author_rank: Newbie
timestamp: October 29, 2023, 04:54:31 am
content: I will disagree with some statements about how robust are LED lamps. For many years I was using for outside decoration incandescent bulb.1.)If snow covered them then next day lamps melted it and appeared again. LED is cool so was lost buried by snow. This can be fixed shaking off snow from the branches, but still1:0for incandescent.2.)Incandescent lamps had some kind of non corrosive wires contrary to LED which has iron wires . After one (max two) seasons they are rusted and not working anymore.2:0

author: Brumby
author_rank: Unknown
timestamp: October 29, 2023, 05:14:12 am
content: Quote from: IanB on October 29, 2023, 12:06:29 amThere was no such behaviour from those lights. (It was Australia pre 1970)

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 29, 2023, 09:44:52 am
content: Quote from: Gyro on October 28, 2023, 10:37:20 pmThat's actually a nice find, I've been hoping that somebody would produce coloured caps for LED lights. Thanks for the very useful link, it's giving me some more ideas and I see via an Ebay search that there are also caps for 5mm LEDs, etc. For example:https://www.ebay.co.uk/itm/374214367617

author: SolderSucker
author_rank: Regular Contributor
timestamp: October 29, 2023, 09:46:27 am
content: Quote from: AndyBeez on October 28, 2023, 11:36:10 pmThanks, I see the one that you provided the image of:https://www.amazon.co.uk/Mercury-DMR-1WHT-Plugin-Dimmer-Switch/dp/B000LAU04K/I think I'll give it a go. Noted about changing the fuse in each string's plug to 3 amps.One question though - I plan to plug three strings (each consisting of 100 filament bulbs) into a multiway adapter and then that into the dimmer. Any potential problems there? Each string is rated at 33 watts, the linked adapter is 300 watts so should be fine.

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 01:47:58 pm
content: QuoteThe flicker might be a problem for some,but for those of us who put fluorescent starters in series with there lights its another flashing effect

author: IanB
author_rank: Super Contributor
timestamp: October 29, 2023, 04:37:01 pm
content: Quote from: themadhippy on October 29, 2023, 01:47:58 pmThere are people other than you who do that?

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 07:26:29 pm
content: QuoteYep,bucket loads,was a very common method of achieving a fire lighting effect in theatre and film

author: AndyBeez
author_rank: Frequent Contributor
timestamp: October 30, 2023, 06:24:30 pm
content: Quote from: SolderSucker on October 29, 2023, 09:46:27 amThere might be a sight imbalance when cold starting as one string is likely to have a series resistance lower than the other two. And one string might be brighter just because of the bulb rating, but in theory, it work out okay. Let us know how you get on.

author: RJSV
author_rank: Super Contributor
timestamp: October 31, 2023, 04:12:18 am
content: I enjoyed experimenting, with individual mini-lamps, although I didn't consider the issue of self-shorting types...(Yikes!).One curious phenomina that occured was a variation of lamp 'HALO' visual trick; Somebody had built a room decoration where a little red bulb was positioned precisely in front of a blue mini-bulb. The trick effect was that the red mini-lamps appeared to have a BLUE aura! You had to move your head around a bit, to discover what was going on.Wouldn't hurt to downgrade the volts, some, using 2.0 volts vs. 2.4 standard. Don't forget that's AC rms, in those 'old days' (1992). I think the current was somewhere around 40 to 100 mA each, which is a fairly fast drain, on small battery...certainly won't last more than one night.Some guitar effects, such as Fender amp tremolo have used the softer response of a filament lamp / with LDR (light dependant resistor), for modulating volume.

author: andy2000
author_rank: Frequent Contributor
timestamp: October 31, 2023, 05:31:36 am
content: Quote from: NiHaoMike on October 29, 2023, 03:53:20 amI've been doing this for years for incandescent light sets which are too bright. It doesn't cause noticeable flicker to my eyes, and I'm very sensitive to the flicker of most LED light sets. One of the main reason I don't use LED Christmas lights is because almost all of them look like strobe lights to me.

author: lezginka_kabardinka
author_rank: Regular Contributor
timestamp: October 31, 2023, 07:39:34 pm
content: Quote from: mendip_discovery on October 28, 2023, 06:32:28 pmJust because LEDs are the latest obsession, plastered in, and on EVERYTHING, doesn't make them "better" for EVERYTHING. He wants filament, and I am with him on this; they are vastly superior.

author: Sredni
author_rank: Frequent Contributor
timestamp: October 31, 2023, 08:32:41 pm
content: Incandescent camp here.The atmosphere is unique. I mostly use strings of 10 and 20 bulbs, rated for 24V and 12V. When my country moved from 220V to 230V I had to endure "The Great Burning" due to the reduced lifespan when running at a higher voltage.Being lazy, I simply went through dozens of strings, at least four per season, until I had enough and put a diode in series with them. 'Half' voltage, quarter power they became eternal. And in my eyes, they even look better.There are different ways to reduce the voltage:- single diode- two series of 10-20 diodes in parallel, with opposing orientation- series capacitor- a 12 to 24 V transformer to wire in series so that the voltage is subtracted from the mains voltage- a full blown variac (but that's overkill)Or even adding 3-4 extra lamps to the series (but they need to come from the same batch)To the OP, my advice is to power a single bulb with a variable voltage source and record the current. Once you reach the right brightness you should find the operating voltage (in case it's one of those string where multiple series are in parallel).

author: IanB
author_rank: Super Contributor
timestamp: October 31, 2023, 09:01:17 pm
content: Quote from: Sredni on October 31, 2023, 08:32:41 pmOr a simple phase angle lamp dimmer? These are simple, commodity items, plug and play.

author: Sredni
author_rank: Frequent Contributor
timestamp: October 31, 2023, 09:10:42 pm
content: Quote from: IanB on October 31, 2023, 09:01:17 pmThe ones I have always used for my light fixtures had a minimum power requirement of a out 100W. Iirc they buzzed when used at lower powers, or maybe they just didn't start. I never bothered to search for a more adequate product.

author: IanB
author_rank: Super Contributor
timestamp: October 31, 2023, 09:14:41 pm
content: Quote from: Sredni on October 31, 2023, 09:10:42 pmThat's odd. I have never encountered one with such a high minimum power requirement.

author: Zero999
author_rank: Super Contributor
timestamp: November 01, 2023, 01:36:28 pm
content: Quote from: IanB on October 31, 2023, 09:14:41 pmI would expect the minimum power requirement would be higher on 230V, than 120V, since the power is double, given the same current. I don't recall a dimmer with a minimum load of 100W though. 40W is most common.

author: Sredni
author_rank: Frequent Contributor
timestamp: November 01, 2023, 09:18:09 pm
content: Just checked it: they are rated for loads with power comprised between 100W and 500W.These were bought more than 15 years ago.There are newer versions that go from 40W up (to 200W max), and even some with a minimum requirement of 10W.I need to refresh the theory on how to design these things...