Hi everyone,
First, I'll admit, I am a NooB. I haven't really done anything electronic since physics II in university, and even that was limited to basic understanding. I hope some of you can bear with this post, and hopefully, thread.

I'm trying to build a bright display for my babies' room using Luxeon III's as illumination. It will be multicolored, don't know if it will be a rainbow, or a lightning bolt, but there will be a (white) illuminated cloud, too.
I'm using Luxeon III's, because they are basically free at work, as long as I can prove I used them, not sold them.

My problem, of course, is the driver. I saw the Xitaniums sold by futureelectronics, but I understand they can only handle 4 LEDs at a time, and would be expensive. The buck pucks seem the same. I really want to get this in under the wife's budget, and nose!

Here's the data for the LEDs, so you don't have to look at the info elsewhere:

At 700mA blues, greens have a forward voltage of 3.03 (min), 3.7 (avg), and 4.47(max)

At 1400mA, (I'll only run them at 1000) reds, oranges, amber have a forward voltage of 2.31 (min), 2.95 (avg), and 3.51(max)

I saw some drivers at www.hobbytron.de from http://www.constant-current.com/html/hko_.html. They caught my interest because they cost only 16 euros each...

HKO700 constant current power source

startup ca. 5.8V (for one 3 Watts LED)
drop:ca. 2.5V
Max input voltage: 35 Volts
700mA constant output current
Input: reverse polarity protected
Tolerance <3%

Says it can drive with constant current up to 10 High-power LEDs in white, blue, or green, or up to 16 high-power LEDs in red, amber or orangs, depending on input voltage.


HKO1000 constant current power source

startup ca. 6.8V (for one 3 Watts LED)
drop:ca. 3.5V
Max input voltage: 35 Volts
1000mA constant output current
Input: protected against confusion of the poles
Tolerance <3%

Says it can drive with constant current up to 10 High-power LEDs in white, blue, or green, or up to 16 high-power LEDs in red, amber or oranges, depending on input voltage.

These say I can run 10 Luxeon IIIs off of each. I was planning to run 10 blues and greens off of a 700mA unit, and 10 red, orange, and amber one off of the 1000mA model. Do the numbers work out? Will they do the job? Could you recommend a better (lower cost) off-the-shelf solution?

What would it take to get these power supplies to work from a 220V standard european outlet?

I emailed the manufacturer, but never got a reply. Can anyone here help?

My only constraint is time. I have to get everything soldered (not running) by February 17th, before our next inventory.

I appreciate any help or assistance anyone could give.
Thanks.

 

I hope your baby doesn't look directly at those extremely bright LEDs. Blindness might result. Use the LEDs for indirect lighting for safety.

Hiow are you going to cool the high-power LEDs?

__________________
Uncle $crooge

 

Have you considered using a simple series resistor?

The formula is:


Use a mains adaptor to safely power them off the mains.

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I was going to heat sink them onto some extruded aluminum rails, stuck on with either some Arctic silver or some kind of conductive epoxy.
I thought maybe some conductive tape, but after I read some here, I decided against it.

The LEDs would be placed behind opaque plexiglas or other plastic so the colors would seem to blend. I do want it to be somewhat bright, though. I checked out the blend effect with some of the same kinds, just individually mounted on little aluminum blocks behind some of the same plastic, so I already have an idea beyond "mental" visualization. I do appreciate the concern, though.

Do you mean a resistor between the mains adaptor and the LEDs?
I thought a constant-current power source would be best, from the literature, anyways.

I was planning to make three different arrays, in strings of ten, each having its own dedicated constant-current power supply. The ones I wrote about (the HK700 and HK1000) were the most economical -if they can really handle a 10-unit array- for the job, after considerable googling under "LED driver".

Thanks so far!

 

Yes, I mean adding a resistor in series with the LED.

A constant current source is recommended but it isn't that improtant, especially if your suply voltage doesn't vary by much.

You can make a constant current from an LM317 regulator, the circuit is on the datasheet which can be found from Google.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

The forward voltage of the LEDs varies a lot. Maybe they are all from the same batch and are 3V or maybe they are all 4.5V. Testing the forward voltage with a resistor might blow them up.

Test with a regulated current source, record the forward voltages, connect a mixture of their voltages in series then caculate a current-limiting resistor for each series string.

__________________
Uncle $crooge

 

So it's not as easy as solder them all in series, and connect them to the power supply, no transistors because the current is constant?

I was under the impression that I could just add the voltages (the typical voltage) keep it a little under the what is supplied by the power supply's delivery, and that everything would be fine...as long as I used the 700mA ones and the 1000mA ones all on their own supply.

The drivers have a maximum output voltage, which I understand I can't exceed, and they keep the current constant, so I shouldn't have to worry about using resistors. I just figured these "plug and play" devices would do their thing for me.

 

You do need current limiting, you can't connect a 3.3V LED to a 3.3V supply and expect it not to overheat. You could connect it to a 4.5V supply with an approprietly sized series resistor.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

Your constant current drivers might not be able to drive 10 LEDs in series if their forward voltage is high and adds to more than 31.5V and 32.5V. Maybe only 7 LEDs in series. you don't need resistors if they are used. You will need a power supply with no more than 35VDC output.

__________________
Uncle $crooge

 

Why do you need no resistors with a bunch of leds in series? Have a look as suggested at the LM317 as a constant current source & be sure about it. It's such a simple circuit you can implement it with chocolate block / terminal strip.
2 resistors, one chanky regulator.

Check if you need a heatsink with it though.

 

A constant current source is an automatically adjusted series resistor.
It adjusts its resistance to keep the current constant.

A series voltage regulator IC is also an automatically adjusted series resistor.
It adjusts its resistance to keep the voltage constant.

__________________
Uncle $crooge