# 60ct. LED Christmas Lights at Target



## ClubTepes (Jul 31, 2002)

Thanks to FourMadMen for pointing me to those LED's at Target.

What I found was a few brands who are producing LED christmas light strings.

I believe I piced up that same kind as what 4MM told me about (blue metalic box).
Those happen to be by Philips and run about 12 bucks with 60 LEDs on the string and two extra.

So now I have a few questions for those LED gurus.
I always believed that LEDs operated only on DC current.
This string of X-mas lights has no transformer to convert AC to DC.

Now even though this strand of lights is bulky, It may be possibly to use them inside the PL Refit as is, as a cheap alternative to buying a bunch online and doing a lot of soldering wiring etc. 

But in my case, I had always planned on using a 12v. DC power source to do everything and keep the wiring coming out of the hull to a minimum.

The question for the guru's is.......whats going on with the whole AC/DC thing and if I pull the individual LEDs out and re wire them into my 12v. DC system, how might I figure out the needed resistance based on the fact that there were 60 in a 110v. sting.
(I've done that ole' resistance calculator thing for the ones that I've bought before where I knew the draw etc.).


----------



## fluke (Feb 27, 2001)

That is a good question! 

Come on! some one has to know this stuff?


----------



## Four Mad Men (Jan 26, 2004)

Actually if you meter your receptacle you'll probably find (depending upon the age of your wiring) around 117V coming out of it.  Anyway...

There is no rectifier to be found on this strand but what you will find is that it's wired in two sets of 30. Each set wired with opposite polarity. The net effect of this is that only half the bulbs are lit at a time. However at 60Hz you may or may not notice it. What this also means is that when you apply 4V DC current it's likely to brighten as it will be under a 100% duty cycle vs. the 50% duty cycle on the AC strand.

As for the resitance itself just go to one of the many calculators for this on the web and use 4V for one LED and 20mA for current.

120V @ 20mA = 2.4Watts * 2 sets of 30 = 4.8 Watts (as stated on box).

Now all that's assuming I'm not talking out of my "bottom". Please take the above with a considerable helping of salt.


----------



## ClubTepes (Jul 31, 2002)

Four Mad Men said:


> Actually if you meter your receptacle you'll probably find (depending upon the age of your wiring) around 117V coming out of it.  Anyway...
> 
> There is no rectifier to be found on this strand but what you will find is that it's wired in two sets of 30. Each set wired with opposite polarity. The net effect of this is that only half the bulbs are lit at a time. However at 60Hz you may or may not notice it. What this also means is that when you apply 4V DC current it's likely to brighten as it will be under a 100% duty cycle vs. the 50% duty cycle on the AC strand.
> 
> ...


Thanks 4MM.
What you say makes a lot of sence, but I thought it was bad to run current backward throught a LED. (which is in eccence what is happening half of the time due to the AC power).


----------



## GLU Sniffah (Apr 15, 2005)

4mm is correct. That is exactly how they work.

http://led.linear1.org/led-christmas-lights-from-philips/2/

In fact, everything you want to know about LED's and their operating requirements and circuits to drive them can be found here: http://led.linear1.org


----------



## toyroy (Jul 17, 2005)

ClubTepes said:


> Thanks 4MM.
> What you say makes a lot of sence, but I thought it was bad to run current backward throught a LED. (which is in eccence what is happening half of the time due to the AC power).


Actually, with a diode, no current flows in the other direction. As was mentioned, when the current is running the opposite way, those 30 LEDs are off.


----------



## GLU Sniffah (Apr 15, 2005)

Diodes must be forward-biased to conduct.

They are semiconductors.


----------



## F91 (Mar 3, 2002)

Side note- Voltage out here is minimum 120V and lots of times higher.


----------



## modelsj (May 12, 2004)

*l.e.d.'s*

Putting the technobabble aside, this is an inexpensive solution to mr refit lighting. I bought two white and one blue set. When hooked up to six volts they are still bright and will work really well as the spots, as they are really directional. If I put white and blue together, I get the bluish light effect from the windows, not the intense white.


----------



## toyroy (Jul 17, 2005)

Thanks ClubTepes and FourMadMen, for the Target LED set tip; I bought one white set today. We have an older Target, and a new bigger store close by, so I compared what was available. The bigger store had a few more varieties, but the best deal was the same 60 light set mentioned before.

I'm going to start another thread, on another similar deal I found.


----------



## Trekfreak (Mar 26, 2005)

*Christmas Lights for Refit*

Someone just put up the suggestion of using Christmas lights to light up the PL Refit. Good Idea or Bad Idea? And if good any recommendations?


----------



## modelsj (May 12, 2004)

*l.e.d. lighting*

If you buy these l.e.d. sets to put on your tree they are expensive and they look stupid with a.c. power. But to use them for model lighting they are inexpensive and you do not have to wait or pay for shipping. 60 bright l.e.d.'s at .20 a piece is a good deal. At Radio$#*@, they are 1.99 a piece!


----------



## ClubTepes (Jul 31, 2002)

Trekfreak said:


> Someone just put up the suggestion of using Christmas lights to light up the PL Refit. Good Idea or Bad Idea? And if good any recommendations?


Bad idea.

Compared to LED's, they burn out quickly, generate heat, and if you leave them in series, if one goes out......they all go out.


----------



## ClubTepes (Jul 31, 2002)

One final update from me on this thread.

I hadn't really dug into these LED strands yet. Just picked one up looked at it and forgot it until the other night when I contemplated how I was going to wire them up in that big chunky housing.

I thought I might dig into one and see how hard it was to free one from the housing.
Turns out its DARN easy.

Just bend the leads back to straight, then you can just push the LED out of the housing. One could probably undo a whole strand in about 15 minutes.

I think I'll go back and see what other colors they offer.
Might just have to build up a whole supply for whenever.


----------



## beeblebrox (Jul 30, 2003)

Bought a white set last night. Started unwinding some wires and found that it is two sets of 30 lights wired in series. I separated the two sets and removed the wire that only serves to get the "negative" wire to the female plug for stringing sets together. I plan to put one set in the saucer and the other in the lower hull and nacelles. Then I'll run them both back to the male plug. 

I have a question. How much would it overpower the LEDs if I removed one or two from each strand? I don't neccessarily need all 60 lights.


----------



## Steve244 (Jul 22, 2001)

uh you wouldn't be UL approved, you'd have a fire hazard, and run the risk of electrocuting someone with 120V to the model.

That said, removing one or two will probably stop the thing from working. If you make the circuit around the missing LED the rest will light, a little brighter. I wouldn't recommend this.

What I do suggest is you remove all the LED's and wire them in parallel with supply voltage of 6 or 9 volts DC with an appropriate resistor to protect from burning them out.

A 300ohm resistor on each LED with 9V supply would be fine (probably not as bright as possible).

Otherwise you could assume (for white LED's) a voltage of about 4V each, string 2 or 3 in series and light with 9V. Experiment: see what happens. Then gang together groups of LEDs (2 or 3) and run 9V. Either use batteries (high amps) or a regulated power supply of sufficient amperage (depends on how many LED's you use).

Please don't run 120V inside your model.


----------



## beeblebrox (Jul 30, 2003)

Steve244 said:


> Otherwise you could assume (for white LED's) a voltage of about 4V each, string 2 or 3 in series and light with 9V. Experiment: see what happens. Then gang together groups of LEDs (2 or 3) and run 9V. Either use batteries (high amps) or a regulated power supply of sufficient amperage (depends on how many LED's you use).


No resistor needed?
I've done a lot with 12v incandescents, but LEDs I'm not real experienced with.
Thanks for the fire & shock warning. :freak:


----------



## Steve244 (Jul 22, 2001)

well, experiment. I'm guessing these LED's are pretty tolerant to over voltage seeing how house current can vary 10% or more. Two 4volt LED's would prefer 8V (not a common source). 9 will be bright and may shorten their life (like maybe reeaaaaal short), without a resistor. try 3 in series (12 volts) on a 9V source and see how that looks. They'd last forever at that voltage without any resistor. I think.

I'd be anal and put resistors on each one wiring them in parallel. But I'd probably get bored and never finish it so don't listen to me...

Key is experiment.

with low voltages.


----------



## beeblebrox (Jul 30, 2003)

I put 3 in series with 9V and it looked plenty bright. Bought a 9V 1200mA transformer. Any guess on the mA of the LEDs? I'm guessing no more than 30mA each, so I think I can run forty LEDs.


----------



## Steve244 (Jul 22, 2001)

Sounds good. 20mA to 30mA. A less expensive transformer may not regulate the voltage well so it may be high with few LED's hooked up.


----------



## guartho (May 4, 2004)

So what size are these LEDs? And do you know or have an estimate of their candle power?


----------



## guartho (May 4, 2004)

Is this the string you guys are talking about? It looks like it to me, except they list no white strings. And it says they're "faceted" but they don't look faceted in the picture. 

In any case, they're out of stock so I'll have to walk-in anyway, but I was trying to get an idea of size, etc.


----------



## frontline (May 4, 2005)

guartho said:


> Is this the string you guys are talking about? It looks like it to me, except they list no white strings. And it says they're "faceted" but they don't look faceted in the picture.
> 
> In any case, they're out of stock so I'll have to walk-in anyway, but I was trying to get an idea of size, etc.


Those are indeed them. They do make the strings in clear as well. So I bought a pack of clear and a pack of multi ********. Since you can swap the bulbs out, Im gonna pull some of the clear bulbs out and repalce them with the red, blue, or green as needed. Sure this wont allow me to get any of the striboes, but ya know what, at this point I can live with that. Now all I have to do is pull these apart and start to rewire them so that I have a decent chase of wire through the model.


----------



## ClubTepes (Jul 31, 2002)

Heres a few possibilities.

1. Cut the string into groups of three. 
Then you should be able to use a 12v. power source without adding any resistors.

2. Take each LED out of its plastic housing. I did half a sting that way and it only took about half an hour.

Don't forget to pick-up a string of the multicolored ones for all the other running lights etc.

I think its pretty cool that for about $24.00 you can have an absolute crapload of LED's to do pretty much anything with.


----------



## frontline (May 4, 2005)

I gotta agree, this is quite a bargin. But I have a question, why do you suggest cutting and splicing the lights into groups of three so you can use a 12v power sourge? I was thinking that I would just power them by plugging the lights into an electrical outlet. Am I missing something?

Also, what am I missing about taking the lights out of their plastic housing? 

Sorry to ask what may be dumb questions, but Im a n00b to lighting


----------



## Four Mad Men (Jan 26, 2004)

Running household AC through a model is not something I'd recommend for (various) safety reasons.

Also, if you are going to try things without resistors please check the light output of the whole circuit prior to installation. Differences in manufacturing can cause one LED (in a group of otherwise "identical" LEDS) to comsume more current than the others due to differences in voltagedrop across the LED. Which shortens the life of that LED and robs the others of brightness. Multiply that possibility for all the parallel sets (of series) in the circuit and you can get most undesireable results (i.e. inconsistant levels of brightness). The good news is that when the "HOG" LED burns out (and potentially takes out the rest in the series due to overvolting) there is a chance that non of the others will take it's place at the table (so to speak).

So even though using resistors will eat some of the battery power it's a safer (albeit less efficient) long term setup.


----------



## StarshipClass (Aug 13, 2003)

I picked up a couple of boxes of white and one of blue--most excellent deal! (Not much use getting the multi-colored since the red and green LEDs are cheaper from electronic supply catalogs and websites.)

Thanks for pointing it out 4Mad and Club!


----------

