Hi everyone,
I’m building an FTIR setup, i bought 150 OSRAM SHF485’s i was planing on using 112 of these emitters along all 4 sides of an Acrylic sheet 80x60cm (32’x24’… I’m now thinking its a bit of an overkill. What are your ideas? How many emitters should i use to get good bright blobs? and Will having more emitters be beneficial in a brightly lit environment or in an environment with sunlight?

As well as using the LED series/parallel array wizard http://led.linear1.org/led.wiz i found out i need around 1.4A from a 12V power supply, i was thinking about using a computer power supply say around 400W~500W, since i will already have a computer within my box? What are your ideas on that? would this power supply be enough? or should i connect my Array to an adapter and not connect with the computer power supply at all?

Thanks in advance for the help.
Taha

Yes, 112 does sound a bit of an overkill. Most people seem to be getting good results with one led at every inch, or ~2.5 cm. And it would even be enough to place the leds along only the long sides.

This way, you would have 32 leds along each of the two long sides, for a total of 64 leds.

In addition, you could angle your leds in order to brighten your blobs. Although, you would have to play around with the rails to find the optimal angle.

I was going to do the same thing with my ~48’x24’ and eventually settled on 64 (32 each short side) out of laziness.  Wiring all those LEDs is a pain in the butt.

hmm yeah i just got my leds today… and a 112 does seem a lot looking at them. Lets see i’ll probably make the 2 rails first and then see if i need more. So yeah does anybody know if i have more IR emitters will the setup be more robust under direct sunlight?

i experimented with using a computer power supply.  works fine but don’t plan on running the computer while you are turning on/off the led array.  the surge will freak out your mobo!

@beeduul: yeah i know what you mean… Thats why i settled for 12V 3A separate DC Power adapter. To power the Leds on and off.

Taha

I plan to use 70 SHF485-s for my 87X66 cm FTIR, 14 on short sides and 21 on long sides, also will have reflection surface around leds inside the frame, so think will give more IR light.

I have an idea to make a sandwitch frame: topp and bottom frames will hold the acrylic (and rosco) and there will be PCB stripes in the middle, mounted on bottom (or top) frame

My advice put 35 leds on both top and bottom you should have them 1 per inch and only on the long edges to get bright blobs.
As for your frame idea it seems good but before you start construction, my advice is to design your frame in google sketchup, it’ll help you solve a lot of construction issues. from what i understand you plan to make a frame similar to the picture below. I suggest you take a look at these threads as well http://nuigroup.com/forums/viewthread/1828/ and http://nuigroup.com/forums/viewthread/1102/

Hope it helps, and if you want to see the frame i made take a look at my blog.

Taha

here is my concept:

ohh very cool i wend a slightly different design, but yours will work out great. cerupcat did something like you did…

Taha

Taha thanks,

I would love to have top and bottom metal frames cut from one piese of metal, somewere 3-4 mm thick and top one thinned down to the screen - towards inner edge, like regular monitors have, but here, in my evnironment, too much time and nerves will be needed to make it, so, I will make wooden, first..  The frame is quite a wide, because I want: 1. to hold well the rosco; 2. have enough space for my ledstrips, which are inserted in special holders, so I can remove leds easily, if I need; 3. to tighten al 3 layers together firmly, as plexiglass is quite heavy. So frame can be movable to other style screener, like wall type, I can have table, and wall and move the frame with the screen to one or other.

as for leds, I am sure 14+21+14+21 will be quite bright, considering also, that I wil have reflector finish of the place around leds I have sections of 7 leds, that give simplest connection and optimal power with only one type resistor (so I dont need to have different calued res-s). well I can actually make 21+28+21+28 (98 led) max, I have only 100 osrams

Im not saying it will not work, but from what i’ve read and experienced my self is is that placing the leds 1” apart produces the best results, i personally went with a total of 150 leds and place them on all 4 sides, for my 80x60cm screen. Im sure it will work but dragging may prove to be a little difficult you will most certainly need to use a compliant surface. Ohh and before i forget to tell you, the shf 485 are super bright, so the first 1~2 inches of the plexiglass is unusable mainly because its soo bright, you willo need to mask that,for that i used Aluminum tape its not very expensive and it works great not only does it mask the IR but it will also reflect the ir back into the plexi making sure none of it escapes from the edges. the edges of my frame are pretty much wrapped in it…

Taha