Suggestions for backlight? - Electronic Circuits Projects Diagrams Free

Lac · 15th August 2004, 12:01 AM

I need to give backlight to a diffuse (sandblown) plexiglass that is about 10cm x 40cm (4" x 16"), the plate is mounted on the wall, and the less space there is between the plexi and the wall, the better. If the light could be nice and even all over the plexi, that would be awsome.

Thoughts that I have, to solve this, is to either use some (3) really strong Lumileds and the sand the lenses down a bit to give the light a diffuse look, or use a lots of standard leds in a grid array behind the plate.

But the problem is that it isn't just ONE plate i need to light up, but 42!

ops: So, I need some good ideas to work this out. Any ideas would be greatly appriciated!

Cheers!
Lac.

Oznog · 15th August 2004, 05:08 AM

Luxeon makes far more powerful LEDs than Lumileds, but they're also quite expensive if you're doing 42.

The key feature is that Luxeon makes a "side emitting" LED which may be exactly what you're looking for.

http://www.luxeonstar.com/item.php?i...rtno=LXHL-FW1C

If that doesn't work, they also make a "Lambertian" LED lens which spreads the luminuous flux evenly over a full 180 deg spread. It will still be brighter in the middle, since this part of the glass is closer to the LED.

Lac · 15th August 2004, 05:40 PM

Thanks. After doing some research I have settled on this type of LEDs. 1310 MLM, 70mA, 35 degree. How much is 1310 MLM rated in MCD btw?

So, do you think these will light up properly if I put seven of them behind each panel?

Cheers!
Lac.

Lac · 17th August 2004, 03:25 PM

Ok, I just ask you guys to look over this and see if I have calculated it all right:

So, now i have decided to put 6 Leds behind each panel in serie with a resistor at 18ohm 1/4W. simple ohmslaw:

6leds x 2,3V = 13,8
15V - 13,8V = 1,2V
1,2V / 0,07A = 17,1428...ohm = 18ohm.
1,2V x 0,07A = 0,084W

---

All the LEDs wil then draw 2,87A from the PSU

1,2V / 18ohm = 0,066666...A
42plates + dots = 43plates
43plates x 0,066666...A = 2,87A

---

This load will be split between two 7815s, with can deliver 2A each. When i say split I mean i cut the whole circuit in half, 22plates at one regualtor and 21 at the other, around 1,5A at each. With a big heatsink (fan?)

The powersupply delivers 3,2A at 19V (60,8W) wich should be enough.

---

I think have done it all right, just wanted to double check my work.

Cheers!
Lac.

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15th August 2004, 12:01 AM	(permalink)
Lac	Suggestions for backlight? I need to give backlight to a diffuse (sandblown) plexiglass that is about 10cm x 40cm (4" x 16"), the plate is mounted on the wall, and the less space there is between the plexi and the wall, the better. If the light could be nice and even all over the plexi, that would be awsome. Thoughts that I have, to solve this, is to either use some (3) really strong Lumileds and the sand the lenses down a bit to give the light a diffuse look, or use a lots of standard leds in a grid array behind the plate. But the problem is that it isn't just ONE plate i need to light up, but 42! ops: So, I need some good ideas to work this out. Any ideas would be greatly appriciated! Cheers! Lac.

15th August 2004, 05:08 AM	(permalink)
Oznog	Luxeon makes far more powerful LEDs than Lumileds, but they're also quite expensive if you're doing 42. The key feature is that Luxeon makes a "side emitting" LED which may be exactly what you're looking for. http://www.luxeonstar.com/item.php?i...rtno=LXHL-FW1C If that doesn't work, they also make a "Lambertian" LED lens which spreads the luminuous flux evenly over a full 180 deg spread. It will still be brighter in the middle, since this part of the glass is closer to the LED.

15th August 2004, 05:40 PM	(permalink)
Lac	Thanks. After doing some research I have settled on this type of LEDs. 1310 MLM, 70mA, 35 degree. How much is 1310 MLM rated in MCD btw? So, do you think these will light up properly if I put seven of them behind each panel? Cheers! Lac.

17th August 2004, 03:25 PM	(permalink)
Lac	Can you guys check and look over my work Ok, I just ask you guys to look over this and see if I have calculated it all right: So, now i have decided to put 6 Leds behind each panel in serie with a resistor at 18ohm 1/4W. simple ohmslaw: 6leds x 2,3V = 13,8 15V - 13,8V = 1,2V 1,2V / 0,07A = 17,1428...ohm = 18ohm. 1,2V x 0,07A = 0,084W --- All the LEDs wil then draw 2,87A from the PSU 1,2V / 18ohm = 0,066666...A 42plates + dots = 43plates 43plates x 0,066666...A = 2,87A --- This load will be split between two 7815s, with can deliver 2A each. When i say split I mean i cut the whole circuit in half, 22plates at one regualtor and 21 at the other, around 1,5A at each. With a big heatsink (fan?) The powersupply delivers 3,2A at 19V (60,8W) wich should be enough. --- I think have done it all right, just wanted to double check my work. Cheers! Lac.