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C7 and C9 lights


Ridders

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Guys -- my first post , so apologies if this question has been asked before. Im in the uk on 240v AC and struggling to find outdoor static strings of lights. I see in the USA you have fantastic cheap strings of C7 and C9 lights that would be fantastic. Soooo my question if i buy a few strings of these lights and wire 2 in series to "spilt" the 240v load into 120v per string -- do you reckon it would work? or failing that can anyone direct me in the direction of a good supplier of 240v light strings almost as cheap as you guys can get them?

At the moment im buying led's with they blasted controllers on them, and then modifying the PCB to give me a constant light, that hopefully my LOR kit will work with when it arrives. It seems in the uk no one is interested in selling outdoor static lights anymore -- i can get plenty of indoor ones, but not outdoor.


Many Thanks

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My (very) basic understanding of AC electricity tells me what you want to do won't work, Ridders. C9 bulbs by design require 120v AC. The strings are wired in parallel so each bulb sees 120v. I guess theoretically you could wire two single bulbs in series, resulting in a voltage drop of 120v across each bulb, but then you'd end up needing a bunch of two bulb strings.

Perhaps someone a little more knowledgable than me can tell us whether a transformer would do the job . . . something to split the 240v mains into two 120v lines. Wouldn't a travel adapter do the trick?

Cray

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Thanks for the reply, what im trying to do is in the drawing enclosed -- in theory it should work, as the voltage should half between the two strings giving me 120v at each string.

Any other ideas?

i think a travel transformer could be used, but would need to be rather large (expensive) for the amount of current it would have to deliver to the lights

Attached files 185854=10539-Untitled-2.jpg

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Yah, I imagine it would take a large adapter, or a slew of smaller ones.

I didn't envision what you meant by "in series". Your drawing clears that up, and is kind of the idea I was referring to with the "two bulb" thing. In theory, it should work. It would be interesting to see if it worked and if dimming response was OK. You might give it a try, using appropriate safety precautions.

Man, this is getting a little like that joke we have over here about the redneck's last words . . . "Hey, watch this!"

Cray

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I don't thing that works with AC current, just DC. I am pretty sure you need a step down transformer to accomplish this task. I am sure you will get definative answers shortly.

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http://www.tlc-direct.co.uk/Main_Index/Transformer_Index/USA_110volt_Convertor_Transformer/index.html

hmmm, not cheap especially if i want to convert a load of channels. I suppose my other option is to go for a complete 110v setup, and use one of the big industrial transformers (we use them on construction work here in the uk to convert us down to 110v for safety on site) to power the full setup. It would certainly be cheaper in the long run, as your light prices over there are so cheap compared to us. The only other conflict i could see with this is we are 50hz supply not 60, although the board is all rectified to DC for the timing etc, so shouldnt be a problem, and the mains section is direct to the lights so should nt be a hastle either

this may be my answer

http://www.tools4trade.com/d-97003-3.3kVA-Transformer-110V.aspx
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Yeah, the more I think about it, the more I'm inclined to think a xfrmr is the better answer. I 'm also thinking Dave is correct -- that the voltage drop thing is applicable to DC and not AC. Sorry, it's been too long since electronics school, and I haven't really used what I learned there in 25 years (and the text books disappeared before that!).

I would keep searching, try the experiment only as a last resort (didja notice Dave's username -- his might be the voice of wisdom/caution), and see what others come up with here in the forums. Surely what you want to do has been done. You could even search the Members Directory for other users living in the UK. Also search the forums for the term UK.

Cray

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Thanks guys for all your help so far. The price of LEDs in the uk is just stupid at the moment, and any i get from ebay / local stores etc etc, all have they stupid controllers on them that i have to modify (heres hoping they work). I have managed to order up a few more LED's and some halogens for this years first show, that will probably be enough for what i want to try out, just to get started, so any more i have to do with the C7 C9s will be for next years setup, which im hoping to increase to about 64 channels.

I have a load of DMX lights, so the dmx add on will be an option for next year, as long as i can get some sort of weather proof enclosures for the lights. I like the look of some of the colour ribbons as well -- they are very cool.

Where do you guys get your LED's from, and are they all statics (i.e. no silly controllers on them)? The reason i ask is that for me to get them from USA would be no hastle for next year, and as they are low power, then transformers would be very cheap to drop the voltage, and im guessing you guys get them quite cheap compared to here. In the uk most places charge about £20 for 100 - 180 LEDS on a string ( and most have they dam controllers on them)

Cant wait for my units to arrive -- i just checked tracking, and its just arrived at customs in the UK today, so should be soon. i have some nice big Rittal external ip68 boxes for the kit and my wiring etc, and a ip68 plastic box to house the main LOR electronics in within the metal boxes. I have lights sitting all over the conservatory, and i now have a plan for all lights -- just need to start putting it into practice -- i have 1 sequence ready :) although it will have to change a lot with the plan i have put together tonight, but hey ho -- im getting excited.

many thanks again

Ridders (Dave):cool:

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Cray Augsburg wrote:

I 'm also thinking Dave is correct -- that the voltage drop thing is applicable to DC and not AC.

No, it will work the same on AC as it does on DC.

This is how minis work. If you have a 10-bulb mini set, then each bulb is 12 volts. The 120-volts is divided by the number of bulbs (10). Likewise, a 50-bulb mini string uses 2.5 volt bulbs.

In this case, it will be like a 2-bulb string dividing 240 volts by 2. It will work fine.

The caveat: The two 120-volt strings you wire in series must be identical! If one of them has more bulbs, or higher-power bulbs, it will drop less voltage, leaving more (i.e. too much) voltage for the other string.
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Glad to hear it, Steven. As I said, its been a while since I studied that stuff. All I could think was loads . . . impedances . . . which led to . . . real and imaginary numbers (oh, yeah, plainary resistance doesn't necessarily involve imaginary numbers) and calculus.

Thanks. This may really help people out.

Cray

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STOP! PLEASE REFER TO SOME ELECTRICAL ENGINEERING TEXTS BEFORE ATTEMPTING THIS!

Sorry for the blunt warning, but it's really important that you fully understand what you're doing before you attempt this, particularly since you're working with 240V. I'm at work right now so I will give you the short version, but I can certainly provide more detail later.

What you're attempting to do is wire two "widgets" (in this case "widget" being a strand of 120V C7 or C9 lights) in series connected to a 240V to effectively drop 120V across each widget. This will only work properly if the load on each widget is the same, i.e. you would need exactly or very very close to the same number of bulbs on each half of the network. Otherwise, you might wind up with, say, 150V on one half and 90V on the other half, etc. You need Ohm's and Kirchoff's laws in order to calculate this. Feel free to ask for more information.

For this reason, I would strongly discourage you from going this route. It would be much better to to use some 240V-120V step down transformers. I'm also not familiar with the legality of this type of setup in the UK.

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Jeff Millard wrote:

as long as the voltage drop across each light is a little under 2 volts, he should be fine. If the string avalanches...

He's actually proposing C-7 strings, not minis, but the balance is still important. If one string loses some bulbs, then its resistance, and thus it's voltage, will rise, putting a strain on other bulbs in that string.
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Electrically it will work as long as the number of lamps on each string is the same, however I do have some safety concerns with this setup. Not only will there be 240v out in the wet / rain to cause a hazard, the outer connection of one string of C7 or C9 lamps will be at 120v to earth when the string is lit.

Use of a 240v/110v transformer is a possibility, but the type used in the UK for building sites will introduce its own hazards. These units have a centre-tap earthed winding, giving an output of 55 - 0 - 55. The outer connection on all C7 and C9 lamps will therefore be at 55v to earth as long as the transformer is connected to the supply. This voltage will still be present once the show has ended, unless the transformer is disconnected as well.

Regards,

Alan.

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