LED Christmas Tree Lights

You're going about it all wrong.

Get the raw LEDs, wire them up, and then connect it to a reasonable sized battery. SHe can carry the whole thing around and the inverter (and it's associated inefficiency) goes away.

The LEDs in the Christmas lights are no different from any old LED, they need a couple of volts. But in order to run them off 120VAC, they have to wire them so they can run off the higher voltage, which means either putting them in series, or big dropping resistors (I don't know how they do it). So in order to run those off a batter, you need the inverter to step up the voltage, and then the LEDs in effect step them down.

Making your own string of LEDs means you can wire them in parallel (or at least in small substrings of only a few in series so they only need 12v or so), and then run them off the battery directly.

You could even get fancy, and have some sort of sequencer to light the LEDs in a sequence of some kind.

Michael

These things aren't really designed for clothing. How are you handling the safety issues?

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The failure to start could be down to the AC waveform...

If not a straight square wave, they are often optimistcally described as a "modified sine" - which to my mind is a bloody lie. Scoping the output of one such beast, it showed three levels: plus & minus volts and a brief stay at Ov on the transition - great... a 1.5 bit sine wave. That is some modification!

I think this is prosecutable as it really bears little resemblance to a sine and should be described as a modified square wave - which it undoubtedly is.

I have some mains stuff that really doesn't like running of my inverter - but it is fine for lead-lamps and my electric saw etc.

depending on your current capabilty, a short can heat the wires up so the insulation burns - way above the 60-70C human comfort/pain threshold... your daughter could get burns if it develops a fault and these might be nasty if they are "wrapped around" her and she cant get them off quickly... at least put a fuse inline of the power

120 VAC from one side of your child's body to the other. This could be lethal, and that is not a joke.

Pay attention here. Lose the inverter. Throw it away, use it in the car while camping, anything, but do NOT strap a 120V inverter to a child.

Learn how to wire up LEDs for 12VDC. It's really not hard, and it's worth the effort to read a book or so when your child's life is at stake.

Good Luck! Rich

And in your spare time, you could learn to bottom-post, which is the USENET convention.

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Ditto that

You couldn't get me in that rig . . . and I play with Tesla coils.

It just isn't smart to drape a child with 120 VAC wires. The battery from the power pack is more than ample to kill. OK - the chance for a short through a vital organ with enough current to kill is not too likely, but it isn't non-existent either. Something totally unforeseen can go wrong.

It only takes about 12 watts, hand to hand or, head to foot, to kill a healthy adult.

If she's not electrocuted outright there's still a chance that a shock at an inopportune time can cause a secondary, more serious, accident.

Wire the LEDs for low voltage, and if you are using a high current battery pack protect the wiring with fuses and size it correctly to keep it from burning.

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I agree ! Play safe !

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Baron:

I was seeing her get splashed by a car going through a mud puddle.

But whatever - it's a bad idea for other reasons, like efficiency, bulk, complexity, that sort of thing.

No Offense, OP, it's just that we do care, and there _is_ a simpler way to do what you want. :-)

Thanks! Rich

Well, I don't know if you've been following the thread so far, but if you feel like you've been left in the lurch, I'll apologize - I just said, "Learn how to wire them for 12V", which was kind of curt. I'd be happy to walk you through how to do that if you want to start hacking your lights - that's kind of what s.e.basics is for. :-)

Cheers! Rich

I have being reading and I think that different colours are different voltages is that right If I want to run in on 12 volts I think that I wire about 4 in series Is this how I would start Rick

Yes different colours have different voltages. Also the current requirements are different for similar brightness.

If you are using a twelve volt battery, the fully charged voltage is going to be around 13.5 v. Keep each colour LED in a single string. Use a resistor to limit the maximum current in each string at the maximum voltage.

So if you have a LED voltage of say 2.3v, that would allow a maximum of

5 LEDs in series or 11.5 volts. If the maximum current flow through the string is 10 ma (0,01 amp) and 13.5v minus 11.5v = 2 volts. Then the resistor will have to drop the 2 volts at 10 ma. Ie 200 ohms.

Use the same procedure for each string.

When you have completed your project, take a photo and let us all see the results of your handiwork.

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Baron:

Easy to imagine all kinds of tragic scenarios.

He sounds like he wants a quick and dirty solution, and hasn't thought it through.

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Check out

Read the critiques - the last seems like it may have a controller problem

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My dollar store has an assortment of battery operated flashing LED gadgets - and the batteries. Might be quicker, easier, cheaper, safer.