xbox hd bluray - try #2 (success)

OK.. I was fortunate enough to have a friend pick me up another xbox hd today. So here's try #2. Long story short, got things lasing @30mA and it seems stable, though not as bright as my last one.

...Two wasted drives. Sigh.



Diode extraction. Used the xacto knife to pop the diode out from the back. An anonymous 5mm can, with the lettering '"SB016L481" across the side. Go figure.



First light, metering up to 30mA this time. I wired three 10 ohm resistors in series to increase the resistance. During my first attempt (using one 10 ohm with pot turned all the way down) the laser came to life at slightly over 40mA, which may have damaged it. This time it came to life consuming 25mA. I carefully nudged it up to 30mA. It occurs to me that each mA for these violet lasers is about twice as significant as a red because of the voltage difference. A 10 mA difference in current is likely quite significant for these low powered violets.



Closeup of the innards. The Meredith housing is getting a little rough. This the third diode it's housed, and I had to rip the last one out and scrape all the glue out before gluing the latest one in.



Lasing...


Unfortunately there's some bad spray around these diodes. It's a rectangle of violet, either end tapering to a yellow color. The diode spot itself can be focused well using the Meredith housing, spray aside. The spray appears to be some sort of reflection/fluourescence from the diode itself. Image below is from my first attempt, after it died. The diode spot became dim and milky, and the spray got brighter.



I'm sorely tempted to turn the power up a few more mA... but once bitten twice shy.

It's little wonder not many people make these. These diodes are very fragile, and there's a lot of room to f*ck things up making even a simple pointer. But it's a rush when you get it working.

Re: xbox hd bluray - try #2

This thing is enchanting. The spot itself is not bright, but sooo many thing glow (fluoresce) different colors when hit. Then it looks more like a 10-15 mW laser.

I really like it at night. You can see the beam easily, but it appears more gray then purple. When you ceiling bounce the spot all sorts of stuff will start to glow.. white laundry, paper.. all sorts of stuff. In the kitchen there's a white light fixture on the ceiling that glows a sky blue color, lighting up the kitchen.

Need to burn it in, had it on about an hour.

It's still going after 3+ hours. Be nice to know a little more information about the diode used in the xbox. Apparently Sony makes the one used in the PS3. The drive innards were Toshiba. So, these diodes may have a slightly lower max current than the ps3 ones. Then again perhaps I just had bad luck. Since they are both used in readers (not burners) I imagine neither are very powerful .. (> 20 mW). Been running it with a 3-5 minute duty cycle, and it doesn't even get warm.

It's hard for me to estimate how powerful it's lasing while consuming 30mA. During the day the spot looks very dim, less than a 5 mW red keychain laser. However considering how bright certain things fluoresce it could be over 15mW. I guessing it's at least 10 mW.

Fun in the dark. Seems more impressive to the dark adapted eye. Well, that's true for all lasers, but the difference is dramatic with this one. The beam is quite visible at night for such a dim spot. I like how it lights up the room with a faint black light glow.

Two light emitting p/n junctions in the image below

Re: xbox hd bluray - try #2

flogged said:

I really like it at night. You can see the beam easily, but it appears more gray then purple.

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It looks gray because of one of the two main types of photoreceptors (the cells that detect light) that your eyes have.  One type, "cones," see color (due to detecting red, green and blue) and detect contrast well, but require a large amount of light for activation.  Rods, on the other hand, are very sensitive, able to detect up to a single photon, but only allow you to see in "black and white".  So, when it starts to look gray is when your cones are not getting enough light and your rods become the primary light-sensing receptors, allowing you to still see the laser, but with no color.

Thought that'd be an interesting side note

[smiley=thumbup.gif] Very good explanation.

Did you say you glued the diode in, if thats the case that may be why the other one died... it would prevent the heat from escaping causing it to burn up.

....lazer..... ;D ;D ;D

rkcstr -

That's a good explanation why the bluray beam is so visible at night. Rod cells have no sensitivity to red, but 400nm is visible to them. Comparing the bluray next to a ~5mW red, at night, the blueray has a much more visible beam.

Couple of graphs of rod/cone sensitivity:
http://hyperphysics.phy-astr.gsu.edu/Hbase/vision/colcon.html#c1
http://www.yorku.ca/eye/specsens.htm

And here for some basic vision physiology:
http://hyperphysics.phy-astr.gsu.edu/Hbase/vision/rodcone.html#c3

You can see things are bit more complex. While there are three types of color receptors in the eye (cone cells), over 95% of them are red/green sensitive, and these are concentrated in the center of the eye. The blue cone cells make up the minority (< 5 %) and are scattered throughout the retina. The blue cone cells are very sensitive and they are able to detect the light deep into the UV part of the spectrum, well below 400nm. Rods cells are very sensitive to light but cannot 'see' as deep into the UV as the blue cone cells. Apparently the lens of the eye absorbs a lot of UV, but I think there's some evidence that with the lens removed people can see well into the UV. This might explain why the blueray spot is hard to focus on, and it's known that people cannot detect as much contrast in blue objects, because we don't have as many blue sensitive cells, and because of chromatic aberration.

Anyway, this might explain why the bluray seem so much more impressive at night. The sensitivity of the dark adapted eye shifts towards the blue part of the spectrum, and both your blue cone cells and rod cells can see it at night, whereas with a red laser pretty much only your red sensitive cone cells can see it.

Very nice job flogged, I'm glad this one is working out for you, although next time try soldering the components to a board just to be sure none of them are touching something they're not supposed to.

wooooooolazer said:

Did you say you glued the diode in, if thats the case that may be why the other one died... it would prevent the heat from escaping causing it to burn up.

....lazer..... ;D ;D ;D

Click to expand...

Oh no, I used a specially conductive thermal epoxy, just for the task:
http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

With the Meredith housing I'm using this is unfortunately necessary, IMO. The housing is meant for 9mm diode cans, so to get it to work with a 5mm can the diode needs to be press fit into a little brass adapter. I glue the diode into the adapter, and then I glue the adapter to the back of the case to ensure it stays centered while focusing the lens. And it should improve heat flow out of the diode... not that this should be a problem with a diode running at 10-15 mW

In a pinch you can still rip the brass bits apart, though it can a while to scrape the glue out.

chido said:

Very nice job flogged, I'm glad this one is working out for you, although next time try soldering the components to a board just to be sure none of them are touching something they're not supposed to.

Click to expand...

I can do better work than this, I just wanted to see it work. Ended up slapping the first 'prototype' DDL circuit I'd made (for the senkat GB red diodes) into the RS case and bent a few wires to get it to fit. It's not as bad as the picture looks, but it's still a mess. Next one will see the driver components properly soldered onto a PCB. Currently I'm using solid core copper wire, so there's no danger of anything moving and shorting out.

The aesthetics of all this does count, especially the case. The RS project box works and is very hand holdable, but it's not very sexy.

I'm really liking these new violet diodes. This will not be the first bluray I make. The fact Bluray diodes are the ONLY visible 'direct' injection diodes (outside of red) also appeals to me

Probably about 75% of the fun in all this is the process of building it.. once complete it's time to make something different.

flogged said:

rkcstr -

That's a good explanation why the bluray beam is so visible at night. Rod cells have no sensitivity to red, but 400nm is visible to them. Comparing the bluray next to a ~5mW red, at night, the blueray has a much more visible beam.

Click to expand...

LOL, you certainly went into a lot more depth than I did. Have you studied the visual system, or just do some research out of interest?

once complete it's time to make something different.

Click to expand...

I couldn't agree more On the shelf in front of me are 5 home made pointers, all different but getting smaller as they progress....

Regards rog8811

rkcstr said:

LOL, you certainly went into a lot more depth than I did. Have you studied the visual system, or just do some research out of interest?

Click to expand...

It was a boring Sunday.. and I did used to be interested in Astronomy. Very cool laser at night.

I will say this.. once the cost on these violet diodes comes down a bit more, MANY purple laser pointers are going to be sold. It's a very cool color, but because the eye isn't very sensitive to it I think a good starting power would be 20-50 mW for most people. Just need to get the price under $100.00, or better yet $50.00 and these things would sell.

Perfect party laser.