Lighting up a Cross

[spencer]

We were given the task of relighting a cross. It was originally lit with rope lighting but it kept burning out. We made a mount and put in 87 5mm LEDs. They are the cheapo DX ones. Drive current is about 10ma. Power supply is a 16v laptop power adapter. LEDs are in 3S29P. Lots of solder joints and about 60 feet of wire later it is done. Pics below.

EDIT: (taken from post #11 after the two threads were merged)

Is there any product that will accept a high power LED and spread the light over a long narrow area? I'm thinking having an LED in the middle and having it spread a couple feet up and down and only a couple of inches wide.

My application is to backlight a cross. There used to be rope lighting in there but it burned out too quickly. Cross in question is here. Cheap 5mm LEDS are fading.

A good LED rope light would be acceptable too but it seems it would be more expensive but if its a better option then it could work.

Another idea I had was shining an LED down an acrylic rod but I'm not sure if it will give even light distribution.

The 5mm LEDS are fading and one string is out already. I need something brighter and more reliable.

 

[TooManyGizmos]

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How long do you expect those 5mm LED's will last ?

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[spencer]

I'm hoping they last awhile. 10mA is pretty conservative.

 

[fyrstormer]

I'm not big on religious symbols, but that looks pretty good.

 

[Ken_McE]

Am I looking at a hollow box that has the cavity lit and some of the front cover is opaque, and some is not?

 

[Illum]

looks like a shell with the led equipped cross was lowered in..

well, judging from the wiring alone you've gave yourself alot of options for future expansions. those wires should be good for at least a couple amps

 

[spencer]

There is no cover on the front. The picture is a little blurry so it looks a bit opaque. The cross was placed on a cavity.

well, judging from the wiring alone you've gave yourself alot of options for future expansions. those wires should be good for at least a couple amps

I don't think high power LEDs will be in the cards. WAY too much light.

 

[Ken_McE]

There is no cover on the front. The picture is a little blurry so it looks a bit opaque. The cross was placed on a cavity

So this is an indoor unit then? Do you have a pic of it lit from a distance?

 

[spencer]

It is indoor. I don't have a pic and probably won't be able to get one. It is in a gym where the lights are on most of the time except during pep rally's and stuff.

 

[TooManyGizmos]

spencer ,

A year ago I got 3 light bars from 4-7's . $50.00 each .
Each are 1 foot long with 30 Nichia LED's running @ 500ma .
After running 12 hours a night for 9 months only half of the LED's are still burning .
The rest are flickering and expected to burn out soon.

That is why I asked you how long you expected them to last.

 

[spencer]

Light Diffuser

Is there any product that will accept a high power LED and spread the light over a long narrow area? I'm thinking having an LED in the middle and having it spread a couple feet up and down and only a couple of inches wide.

My application is to backlight a cross. There used to be rope lighting in there but it burned out too quickly. Cross in question is here. Cheap 5mm LEDS are fading.

A good LED rope light would be acceptable too but it seems it would be more expensive but if its a better option then it could work.

Another idea I had was shining an LED down an acrylic rod but I'm not sure if it will give even light distribution.

 

[DM51]

Re: Light Diffuser

I'll merge this with your orginal thread and move it here to H&M. Combining the 2 threads will give people a better idea of what you are trying to achieve.

You might want to edit post #1 of the combined thread, to update it.

 

[spencer]

Ok thanks.

 

[Magic Matt]

I think you might have issues with burning out because of the way they're all wired in parallel. Each LED string should have it's own resistor when wiring strings in parallel - ie if you have 3S29P then I should be able to see 29 resistors, one at the start of each 3S string... I can't see them.

If the LEDs are working in terms of lighting, I'd suggest checking your circuit. I'm only a beginner in the electronics side of things myself, and I made the common mistake of using one resistor to feed 8P strings of 4S LEDs... they didn't last long and burnt out over a period of about 2 months. I rewired with a resistor on each string and the circuit has been running for 2 years at 8 hours a night with no sign of dimming so far.

I think you might be able to do that with high-powered LEDs, but you'd want some sort of diffusion to make the light more uniform, and you'd obviously need some good heat sinking.

I Know it sounds bizarre, but for that cross I'd probably have bought some 1ft long fluorescent strip lights of the type that you mount in cupboards. You'd need maybe 5, and at about 8 watts a piece they'd probably be as efficient as high power LEDs, plus you just link them up as mains voltage, so no power supply needed.

 

[Linger]

Since its reflecting back into the cavaty, could you get away with a few power leds down the center and have the natural dispertion put light out to each side?
I figure you could probably get enough old cree p4's (before the Q and R bins) to light it up and they would reliabily work for years. Acrylic tubing could spread the light, but for the $2-4 cost of each emitter i'd say easiest is to replicate your original idea but with power leds (cree p4's or similar old outdated quality emiter).
Sure it's $40 in emitters instead of $3 for a bag of 100, but you've already got to do it twice, I think the $40 would be worth not having to redo it.

 

[DM51]

Maybe you could get hold of a string of white LED Christmas tree lights? The good quality ones last a long time, and if you have a proper opaque diffuser the effect should be what you need.