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Rhys
02-09-2009, 01:20 PM
I'm building an LED light panel. If it works ok then I shall build a second and maybe a 3rd.

My plan is to fill a 5x4 PCB with wall to wall white LEDs and to run the whole lot of some AA batteries. A diffusing panel will be about 1/2" above the LEDs and a second diffusing panel an inch above that.

I've already made a start by painting the non-conductive surface of the PCB white to reflect even more light. It'll need two or more coats but I had time only for one just now.

Essentially the plan is to make diffusion light panels powered by batteries with built-in snoots and tripod mounts that will make a highly portable small product studio. Of course it would also be interesting to see just how powerful these light panels would be for general illumination too.

This is what the pre-starting kit looked like:

http://farm2.static.flickr.com/1168/3267764784_d50684d754.jpg

After the first coat of paint. It seems to have gone through some of the holes. I'll have to clean those out later with a pin.

http://farm2.static.flickr.com/1375/3266941853_1d1363c754.jpg

I have to give that a second coat so that it's a smooth white and clean out the blocked holes.

Then I have to solder the LEDs from the first picture onto the board. More on this project as it progresses.

Zoinac
02-09-2009, 04:25 PM
Neat, I like your approach, what kind of LED's are yo using. I know they are available in a whole range of intensities. Depending on how you wire it up you may need more than just a couple AA's to power the whole rig.

I lok forward to seeing the result. I've thought of similar projects myself.

Rhys
02-09-2009, 08:36 PM
The specs of my LEDs are:

Colour : White
Size (mm) : 5mm
Lens Colour : Water Clear
Peak Wave Length (nm) : N/A
Forward Voltage (V) : 3.2 ~ 3.8
Reverse Current (uA) : <=30
Luminous Intensity Typ Iv (mcd) : Average in 12000
Life Rating : 100,000 Hours
Viewing Angle : 180 Degree
Absolute Maximum Ratings (Ta=25°C)
Max Power Dissipation : 80mw
Max Continuous Forward Current : 30mA
Max Peak Forward Current : 75mA
Reverse Voltage : 5~6V
Lead Soldering Temperature : 240°C (<5Sec)
Operating Temperature Range : -25°C ~ +85°C
Preservative Temperature Range : -30°C ~ +100°C

The one I tested worked fine on 2 AA batteries. The voltage is supposed to be 3.8v but 3v seemed to work just fine. Having said that, with the heavier load of up to 150 LEDs in parallel, I might need to go up to a more powerful power supply.

Mark_48
02-10-2009, 04:00 AM
Are you going to use resistors for current limiting to the LED's? I haven't come across any LED's that get wired directly to a source without resistors or other means to control current as of yet.

A few links on wiring up LED's.

http://www.otherpower.com/otherpower_lighting_leds.html

http://www.reuk.co.uk/Using-The-LM317T-With-LED-Lighting.htm

http://white-leds.co.uk/led-wiring-guide.htm

michaelb
02-10-2009, 06:12 AM
You've definitely got too much time on your hands Rhys. ;)

Rhys
02-10-2009, 07:07 AM
Mark... I'll try to run the whole lot off 3V. That's a pair of AA batteries. If I need more oomph then I might well add a 3.5v zener diode and do it that way rather than wasting power through a resistor.

Rhys
02-10-2009, 09:06 AM
Row 1 works well. I soldered the first row and ran it for a few seconds off a pair of AAs. Now I'm soldering row 2. The first batch of LEDs was just 50. I have 300 more (identical) on the way from China. I reckon I underestimated the number of LEDs I'd need for the project. I'll order more when I've run out of what I have.

Hmm... Very much underestimated - I didn't realise how many LEDs each board could take. I shall order more when I finish this board. It's not very time consuming. About 40 minutes to solder 50 LEDs and to test each of the 5 rows.

Mark_48
02-10-2009, 09:30 AM
What, no pics of the first lighting??? And you call yourself a photographer...... shame, shame. :D

Rhys
02-10-2009, 09:47 AM
I'm heading out now to Radio Shack to get some cable. I tested it using the legs on the LEDs. I need to set to and wire it all up (so far). I have since discovered a much easier way of doing the thing but... I want to see how this looks with all its LEDs. I think it has the potential to be very bright indeed.

As I said, it doesn't take too long to solder the LEDs. I think I spent maybe 40 minutes doing it, testing each row as I completed it (which was good because a couple of times I'd missed the connection with the solder and had to rectify the problem).

adam75south
02-10-2009, 10:21 AM
sorry rhys, after seeing this thread i patented this design and sold it to alien bees so you're gonna have to cease your operation.

cdifoto
02-10-2009, 10:58 AM
sorry rhys, after seeing this thread i patented this design and sold it to alien bees so you're gonna have to cease your operation.
That's BS. The US Government never works that fast.

erichlund
02-10-2009, 11:11 AM
sorry rhys, after seeing this thread i patented this design and sold it to alien bees so you're gonna have to cease your operation.


That's BS. The US Government never works that fast.

Not only that, but this very public post is direct evidence that the patent would be fraudulently entered. Looks like the makings of a juice patent war.

adam75south
02-10-2009, 11:19 AM
i'm not backing down.

Rhys
02-10-2009, 03:48 PM
Sounds like some of you would like to copy this :p

I'll write an article about it sometime - when I finish one. I plan on having several lighting setups like this.

cdifoto
02-10-2009, 04:14 PM
Sounds like some of you would like to copy this :p

I'll write an article about it sometime - when I finish one. I plan on having several lighting setups like this.
Better yet, do a seminar tour.

Mark_48
02-10-2009, 04:35 PM
"Holy crap, these AA Duracells pack a shed load of juice !!!"

Rhys
02-10-2009, 08:20 PM
The voltage needed is very low. Putting 300 LEDs in parallel might make the batteries slightly warm but I doubt it.

Rhys
02-11-2009, 09:36 AM
I have to wait about another week for my next batch of LEDs to arrive. I ordered them on February 4th and it takes two weeks to arrive from China. The PCBs came from Thailand.

I made a couple of minor errors on the board I'm building right now but nothing serious. Just got some of the LEDs into places that make wiring the connection between the rows more awkward. I'll resolve that on the next PCB. I'm planning to make 2 or 3 units.

In terms of light output I'll have about 250 LEDs on each board with each LED emitting 12,000 mcd.

In other words 1 Candella = 1,000 mcd. 1 Candella is the amount of light emitted by a single candle. A 100w light bulb emits about 120 Candella.

Now a quick calculation (I assume I'll fit 250 LEDs onto the board). 250x12,000 mcd = 3,000,000 mcd = 3,000 candella (300 candles). And that is about equivalent to a 250W light bulb.

adam75south
02-11-2009, 10:19 AM
all kidding aside, i really am looking forward to seeing what you come up with here rhys.

Mark_48
02-14-2009, 06:41 AM
Now a quick calculation (I assume I'll fit 250 LEDs onto the board). 250x12,000 mcd = 3,000,000 mcd = 3,000 candella (300 candles). And that is about equivalent to a 250W light bulb.

I got to thinking about your LED's and the current draw you may have. When forward biased at it's nominal voltage (3.2-3.8v) and no limiting resistor, one LED may draw about 20-30ma. If you put 250 of these in parallel you could concievably be up to about 7.5 amps for the total array. If your running these at 3.0v the current may be a bit less, but still may be a problem if you stick with AA batteries. Do you have a multimeter that you can measure the current draw at 3.0v?

Rhys
02-14-2009, 09:30 AM
I do have a meter. If could well be that I might need to raise it to 4AA batteries wired in pairs.


My next batch of LEDs just arrived. This week for sure I'll put some more on the board.

Rhys
02-16-2009, 12:40 PM
Well... I settled down to complete the task then two things happened - just as I got to the last 2 or 3 rows, the solder ran out and the tip on the one soldering iron needs to be replaced. Hmm... we all know what that means... SHOPPING TRIP :p

Rhys
02-16-2009, 04:07 PM
Phew the LEDs are now all soldered into place. What I'm working on now is linking the rows together into a single coherent circuit.

I challenge you to count the LEDs!

http://farm4.static.flickr.com/3202/3285546507_e1b011d6f5.jpg