Thread: LED questions, prices, etc

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I came across a site and they sell UV LEDs, complete with the resistor and wire already attached for 12 v aps. For 10 they want $12.99 for 5mm size, 13.99 for 8mm, everything has free shipping.

I checked radio Shack and this other company sounds competitive, in that the resistor is attached already. But I have no experience yet with using LEDs so input and advice is greatly needed and appreciated.

Also I am wondering, would I be able to hook up something like this (or a bunch of somethings like this) in a "remote" spot that has no electricity to a car battery?

I'm sure I have other questions, but can't think of them now.

Oh, I guess I could put their site address

LED Lights Red Blue Green Purple White UV

I like best hong kong on ebay for my leds but I also assemble everything myself.

You can hook leds to any power source provided you apply the right resistor value or step down

Some of our leds are actually hooked to household current

That price doesn't sound bad for 10 since they are already assembled and ready for 12 volts.
A car battery should work since that's probably what they made them for. If you are powering more than one set on the battery make sure they are hooked in parallel (all the positive leads attached to the positive battery post, and all of the negative leads to the negative post.)
I put mine together myself, too and have ordered several times from Best Hong Kong and I have never gotten a bad LED yet. Takes about a week or so to get them, since they are shipped from Hong Kong.

Thanks... I'll check them out. Do you get resistors etc from them also? What would you judge the maximum length wire from power source to LED? Have either of you tried the UV LEDs? Do they offer a reasonable black light effect?

I've tried to find Best Hong Kong at EBay but had no luck.

Also, from what I've been reading, it looks to me like I need to know for sure what voltage my power source will be ahead of time so that I know what type of resistors my LEDs will need. Is that right?

I looked on E-bay and don't see the seller (Best Hong Kong) listed. I wonder if they changed their name.
This E-bay listing looks similar to their old listings:100x 5mm Ultra Violet UV 2000mcd LED Bulb Free Resistor - eBay (item 290246994680 end time Jul-21-08 15:41:01 PDT)

Here's some LED's listed with the resistors already installed like the ones you are talking about:20 x UV LED Lamp Light Set 25cm Pre Wired 5mm 12V DC - eBay (item 280247393979 end time Jul-20-08 18:24:09 PDT)
I think most sellers send the resistors with the LEDs. I'm not sure how many ohms they are rated for.
Most don't say how long the wires are either.
I have used many UV LEDs and they work GREAT ! Almost like a miniature Black Light. I've even made my own spotlights out of them using PVC pipe.
Yes-you would need to know the voltage of your power source for the correct resistor. Or if you solder 4 LEDs together in series you probably wouldn't need a resistor at all, since most LEDs run on about 3 volts DC.
You can aso power them with a 12 volt wall wart (AC-DC adapter).

Thanks DaveInTheGrave... I think I'd like to "take the little plunge" and learn how to do these myself. It is obviously cheaper that way, and I think it would provide more flexibility.

Does anyone know if there is a limit to the length of wire from the power source to the lights?

I think I want to use this to light my "ghost children" scene (another post). Basically I'm thinking I could put a car battery near the base of the swing set, then run the wires for the UV LEDs to the swings. This would allow me to shield the lights from patrons, shine them right on my subjects, and not have to worry about electricity, of which I have none in that area. This would be much better than having to run a generator. So, because of that I would need to know if I can run a long length of wire, say 20'? If not then I'll just power them with small batteries, but since I need to know what I'm powering with before I get the resisters I kind of need to know if there are distance limits. I hope I'm making sense. I appreciate your input.

The longer the wire run the more voltage you loose in the wire. Wire actually has a small resistance that adds up on long runs. Under 100' or so shouldn't be a problem. you can use larger gauge wire to combat the voltage drop. for example use 12AWG wire for your long run, and then you can drop down to 22AWG or 24AWG for the shorter runs.

The light you get from one UV LED is a very small beam and very subtle. The more LEDs you can group together, the bigger and brighter the beam you will get (like with a UV spotlight). So I guess the main concerns are how close you can put the LEDs to your props and how dark is it in the area of the swingset.
It might be easier to illuminate your scene with several UV spotlights, each powered by a 9 volt battery. Then you could put them wherever you want. Also by putting 3 LEDs in each spotlight you shouldn't need a resistor at all.
You'll have to experiment with them some to get the feel of what will work for you.
I would think 20 feet of wire from the power source to the light would be no problem.
Feel free to PM me if you have questions.