Looking for LED

polarweis · 2019-01-26T13:29:50.000Z

Why does it need to be round?

EasyB · 2019-01-26T16:59:20.000Z

Mtnelectronics has the 319A.

Sirstinky · 2019-01-26T17:09:12.000Z

Hi. It has to be round or the stars projected on the walls or ceiling would be square. The stars match the shape of the LED die like if I used an XML-2, or XP-L, etc, and get smaller if I use a smaller LED. If I use a multi die LED, it will show the individual dies in the stars too

Thanks!

Sirstinky · 2019-01-26T17:14:17.000Z

I thought they did, but I checked the Chinese markets first because I didn’t want to spend a ton of money on it. I will check mtn.

Anyone know why the high power LED dies are square?

Thanks

BlueSwordM · 2019-01-26T17:18:00.000Z

@Sirstinky, it’s easier to manufacture a square die compared to a round die.

It also allows for easier placement on the substrate where the die sits.

Cereal_killer · 2019-01-26T17:48:05.000Z

You also get more luminous area in a given footprint as a square than a circle.
I.e. You have a 1x1mm^2 area,
Square surface area = 1mm^2
Circle surface area = 0.79mm^2

So placing a circle die in that same space would result in a loss of 0.21mm^2 of surface area giving off light.

Sirstinky · 2019-01-26T17:57:02.000Z

Thanks for the info. I didn’t know that also applied to the small leds. They make round cob leds as circles, but you’re right that they need to be bigger to make the same amount of light as a square smaller one.

Snoman002 · 2019-01-26T20:41:05.000Z

How is it projecting the stars? Without focused optics I would be surprised if it actually put square stars on the wall.

Sirstinky · 2019-01-27T02:44:20.000Z

Snoman002:

How is it projecting the stars? Without focused optics I would be surprised if it actually put square stars on the wall.

Here’s how it works… it has a hemisphere (11” stainless bowl from Ikea- great for these and vandegraf generators) that’s completely matte black inside so theres no reflection or stray light getting out. It sits on top of a round stand (a cookie tin) also painted matte black that holds the electronics (led driver, switch, barrel connector for the power supply). The lid of the tin holds the led and heat sink (a big one…that little led is rated for 1W and I’m driving it at probably 4W to get useful light out of it). The bowl has hundreds tiny .3mm to .5mm holes (i drilled them all-broke 5 drill bits took days) that make the constellations (all of the ones we have in the western hemisphere). Is super cool and cost like $20 usd to make. The light from the led goes through the holes and projects the stars. It dies this becauase there’s no light being reflected or bouncing around inside the dome, which also helps the light to pass through each hole. The emitter distance also influences the The light source determines the brightness, size, shape, and color of the stars, so it’s a mirror image of the emitter surface/shape, it just gets bigger the farther the light is protected.

I tried 2 different leds and that’s how i found out the issue with square or multi die emitters. I could use a diffuser over the emitter and that would help, but it would reduce the intensity of the light. The best led for this is a round, small, and crazy bright! I have yet to find one…

Lothar · 2019-01-30T13:38:50.000Z

Sounds like a cool project. Do you mind sharing some images of the projector and the starts being projected on the roof?

Lexel · 2019-01-30T14:00:17.000Z

the smaller the die the better it works, the shape of the die is irrelevant if you do not focus by a lens to a single spot

dedomed sst-20 should work great

EasyB · 2019-01-30T14:54:39.000Z

It sounds like the holes in your hemisphere are acting like pinhole cameras which project images of the die on the ceiling.

Maybe you could try putting a mask over the LED to make it round? Like a piece of aluminum foil with a nice round hole in it placed right on the LED. I think the best LED would probably be the white flat both because of its high luminance and because its package is hard and robust, not easily damaged or burned like most LEDs with soft silicone and bond wires. But this LED is not currently available mounted on a MCPCB in the US. It is available from led4powers store. The next best option would be a domeless XPL HI with the round mask.

Sirstinky · 2019-01-31T05:31:16.000Z

Sure. I’ll get them tomorrow. It’s a neat project and was fun to make.

Sirstinky · 2019-01-31T05:47:11.000Z

EasyB:

It sounds like the holes in your hemisphere are acting like pinhole cameras which project images of the die on the ceiling.

Maybe you could try putting a mask over the LED to make it round? Like a piece of aluminum foil with a nice round hole in it placed right on the LED. I think the best LED would probably be the white flat both because of its high luminance and because its package is hard and robust, not easily damaged or burned like most LEDs with soft silicone and bond wires. But this LED is not currently available mounted on a MCPCB in the US. It is available from led4powers store. The next best option would be a domeless XPL HI with the round mask.

Yes! That’s exactly what it is. The shape of the light source is the same unless it’s diffused somehow like if it’s passed through an optic/reflector or diffuser. I thought about doing a diffuser in the beginning when I ran into the issue, but it would make the light dimmer, plus extra stuff to hassle with. I think I’ll get the 319AT from mtn and overdrive it to get lots of light. It will be a drop in pretty much in place of the old one.

Thanks for the suggestion!

Sirstinky · 2019-02-01T07:47:21.000Z

Lothar:

Sounds like a cool project. Do you mind sharing some images of the projector and the starts being projected on the roof?

Sure. My camera doesn’t take good pictures in low light, but you get the idea. I couldn’t get pictures of the ceiling to come out, but I took some where you can see them. It’s easy to make. You can see the hemisphere (Ikea 11" stainless bowl) with the holes drilled in it. There’s the base (cookie tin), lid, and then the electronics, a boost-buck converter to drive the LED, a wimpy 1W China-special LED on a heat sink I made from an aluminum housing from a PC blower fan (over driven- I think I killed it tonight before this post). Everything is painted matte black so there’s no reflections or stray light inside. I had fun making it!

Dome with the stars from the outside

Stars near the dome are brighter

Stars on the wall, you can see the single round die of the LED and uneven phosphor layering

Inside while it's on, you can see the driver, switch, and the barrel connector.

The holes! Hundreds!

DC-DC boost-buck driver that runs the LED and steps down the 12V from the power supply (a wall wart from a 5-port switch)

The LED heatsink made from a big piece of aluminum sheet

1W China-special LED! It's officially deceased (couldn't take the beating of being run at 4W).

Inside the hemisphere is matte black. You can see some of the holes and a dent where I dropped it.

Sirstinky · 2019-02-01T07:53:03.000Z

Lexel:

the smaller the die the better it works, the shape of the die is irrelevant if you do not focus by a lens to a single spot

dedomed sst-20 should work great

Good suggestion. Yes, the smaller and brighter the better. Like a 3mm die?

Lothar · 2019-02-01T08:48:33.000Z

Thanks for the pics. Really cool project, now I want to make one for my daughter!

Sirstinky · 2019-02-01T22:51:23.000Z

Lothar:

Thanks for the pics. Really cool project, now I want to make one for my daughter!

Great! I made mine be for my son. It’s a really fun project to make and you can be creative too. Put on the stars like in actual constellations, or make your own. Here’s some tips…make sure your bowl is thin or it will be tough to drill into it. Regular steel works better than stainless (softer). Use .3mm to .8mm drill bits. A Dremel tool is best. The led has to be as parallel to the bottom of the bowl as possible. A little higher is also fine, but not lower. Use the brightest led with the smallest die possible. 800-1000lm is what I’d shoot for. Higher the better. The inside has to be completely black and non-reflective. Your stars will be more defined. That’s it!

Sirstinky · 2019-02-01T22:54:51.000Z

Hi all. I ordered the Nichia 319AT D440 5000k today from mtn. I’ll put pictures up of the install when I get it. I’ll have to beef up the heatsink though because I plan running it at 1000lm or as my driver allows!

Thanks

Sirstinky · 2019-02-08T07:40:17.000Z

I got the 319 today and installed it. Mtn is great! Fast shipping. I had to adjust my driver to run at 2.7A and 4.2V (around 11W), drilled new holes, new thermal paste, and this thing rips! Crazy bright and doesn't generate a lot of heat. I'd run it harder, but my driver is getting really warm on the transistor and inductor. Plus my power supply couldn't handle much more. Here are the stars now, much brighter. My camera picks them up now. You can see Orion and the Swan with Herculese too. Notice the hex die! If another company comes out with a round die or Nichia releases a brighter bin, I'll upgrade again. Thanks for the help!