LED Only NightClub, Help!

[jplagarde]

I would say "bar" but didn't want to confuse anyone.

I am building 3 bars in Antigua Guatemala, went down there to study Spanish and decided to stay for a while. I would like to use exclusively LED lighting if possible - I'm currently using cheap colored Christmas lights but can't wait to convert them to LEDs. Most lighting is indirect (lighting ceiling from the beams) or lighting the wall behind a column etc.

To drive the LEDs I was planning on using old PC computer transformers that put out 12volts (among other voltages) and anywhere between 25-50 amps. I've been doing some reading in the forums and understand that there can be problems ... I read stuff about over driving, the need for current limiting, rectifiers?, the need for a load on a transformer to prevent voltage spikes that can ruin your LEDs - someone mentioned putting a diode across to prevent this? (don't understand) ..

I was really planning to just wire similar lights (same color and electrical characteristics) in parallel using a resistor on each, and to wire these different parallel groups of lights in series - making sure they had equivalent loads so the current doesn't take the "easy way out," leaving the harder to drive leds unlit.

I was going to use a pot somewhere to offer at least some minimal dimming capabilities.

For the LEDs, I wasn't going to buy the latest greatest most expensive lights, but instead, buy some bright 6000-10000 mcd LEDs off of ebay for about $.10 each. That reminds me, any good thread on understanding mcd and lumens?

I also see RGB lights for less that $1.00 each, would be pretty cool to be able to mix the light myself using analog pots, don't know if that's worth getting into ...

Any advice would be greatly appreciated.

JP

 

[Gunner12]

MCD and lumens don't interchange.

The newer high power LEDs aren't that expensive(depends on where you buy from of course). Cheapest being the Edison Opto at $4.34 shipped(They also have many other LEDs and parts that you might want to look at), cheaper if you buy more then three. Probably much less blue then most 5mm LEDs and has a smoother beam.

I don't really understand how a driver functions so don't ask me about that stuff.

 

[Entropy]

MCD and lumens don't interchange.

To be more specific:

MCD is a measure of intensity at a particular distance.

Lumens is a measure of total light output.

The difference is that a light with a given lumen rating can have different MCD ratings depending on how tight the beam is collimated.

This also means that an emitter that has half the MCD rating of another emitter may actually be more suitable for your application (indirect lighting of a club) - The low-MCD light may likely put out the same amount of light, but will bounce it evenly off of a large area of the ceiling, as opposed to putting a small spot on the ceiling.

It makes it very hard to compare 5mm LEDs with each other (always rated in MCD, not lumens), although most share the same drive current and don't vary too much in efficiency so you can usually rely on 5mms of a given color to all have similar lumen ratings.

Similarly, it makes it hard to compare 5mm LEDs to higher power LEDs that are rated in lumens. An uncollimated Luxeon I might have the same MCD rating as some of the brightest and most collimated 5mm LEDs, but will put out FAR more light - the 5mm unit is making a small bright spot, but the Luxeon is throwing out enormous amounts of light in all directions.

 

[Ctechlite]

Check here for some awesome ideas...

http://www.dmcleish.com/MauiHome/

 

[jplagarde]

Thanks for the clear explantion of MCD and lumens. Totally understand how a lower MCD led with a larger view angle could end up serving me better for my indirect lighting applications.

I'm hung up on how to power these things. I was planning on using a pc power supply 12v 25+ amps, and running the LEDs in series and parallel. My question I guess concerns efficiency as well. Speaking in really round numbers, If I wire them in series I can reduce the 12v's by the voltage drop of each led and end up "showing" each LED its proper 3 volts without using a big resistor - being more efficient than having them all wired in parallel, showing each 12v and having to use a bigger resistor .. Am I correct in this?That being said, I could run 4 long "parallel wired" strands in series (given they all have the same characteristics) and be pretty efficient right?

I've been reading articles about initial voltage spikes and run away current frying leds, and have entertained the idea of using some kind of linear voltage, whether single chip controlled, or some FETs and transistors ...

I found a great article on instructables discussing all the options on how to power LEDs - seems like you can make something for around $1.00 to drive the LEDs safely.
http://www.instructables.com/id/Circuits-for-using-High-Power-LED_s/

Then you can throw a little microchip a "555" to dim the LEDs using PWM i believe.

Lastly at the end, he talks about another type of linear voltage regulator that's all in one piece a LD1585CV or LM1084IT-ADJ.

Anyone have any thoughts on the various approaches, I would like to be able to dim the LEDs.

Thanks for your help!!

 

[3rd_shift]

For a nightclub, it shouldn't be too hard since a darkened environment is often desired.

For dimmability, maybe give www.taskled.com a whirl.
These boards have been quite reliable in all thier forms.

A pc power supply seems to be a good way to provide power.
A lot of very expensive and fragile computer components depend on these every minute of every day all over the world.
Some offer 3.3, 5, and 12 volt outputs from the same inexpensive box.

Tips;
Stars are easier to work with and wire up than bare emitters.
Underdrive is better than overdrive in case of power spikes, and for better efficiency and service life of the leds.
The more efficient and higher quality your leds are, the easier it will be to achieve your goal.
Lots of aluminum, or copper bar strips and panels are good for attaching the led stars onto to keep them cool with.
Use Arctic Alumina adhesive to help stick them on with, even if using small screws to originally mount them on with.
Ornamental diffuser materials can be attached over top of these works of electronic art for good looks.

 

[Ken_McE]

Just for fun, how about each bathroom has three dimmer switches as you walk in, one red, one green, one blue. Let the patrons set the lighting however they want. Also, there are LED faucet lights that light the water when you turn on the tap.

 

[jplagarde]

3rd Shift thanks for your reply, I'll read through all the tech specs at task, they seem to have to controllability that i need but i don't want to pay $20-$40 a board .. I'm going to need a bunch of these things. I'm the type to try to wrestle it myself. I'm looking at using some of these cheap $1-$3 solutions that are mentioned in the instructable I posted above ... looking forward to learning more about PWM.

Ken your idea about setting the mood light in the bathroom is completely nuts - I love it!! There are analog dimmers, but If i get on the PWM bandwagon - no need for the analog stuff. I don't know if anyone has been seeing these LEDs on Ebay, the seller is TopBright, and they seem to have some high power RGB leds on the same chip with 4 leads. To me it would make sense to try to use one RGB light instead of putting separate stars of each color??

Also I know everyone's crazy about stars, but for some of my backlighting applications i was planning on just using some bright 5mms or other standard types that are cheaper with a wide angle ..


Any if anyone has any comments on my series parallel stuff regarding efficiency questions in my previous post please let me know ... thanks!