The XBOX 360 HD-DVD high power laser thread

[climbak]

I don't know what power we're getting out of it. It's not really readily accessable to power testing the way we have it rigged up. His power meter also only goes to 20mW. He does have a 10X attenuator for it, but I am pretty sure it's putting out somewhere along the lines of all the other diodes.

 

[flogged]

Well, 90mA does seem to be a sane and reasonable current to run the 803t diode at.

I put over 35 hours of use on my brick pointer, using 90mA (on page 30 of this thread:http://www.laserpointerforums.com/forums/YaBB.pl?num=1209940381/348).

At 90mA my setup can be left on indefinitely - no duty cycle. The Meredith housing and mounting block - which I've thermal glued some additional copper bits to - does not get more than body temperature warm. I'm also getting outstanding battery life. This is using the 'DDL' circuit (using a rheostat) with 6 AA batteries. The batteries lasted over 30 hours, and they hadn't yet started to fade! It took over a week to get 30 hours of use, I'd leave it on for a few hours each evening.

Tonight I decided to adjust the current up to 100mA. When I broke the circuit to meter I noticed something strange - the current use said 75mA, and I had set it to 90mA before the 30 hour burn. ?? Weird. I then put in fresh batteries and got the same thing. Even stranger, when I turned the pot to where I'd initially measured the diode to 82.5mA (when first completing the pointer) the diode now was only drawing 50mA. It was as if the internal resistance of the diode had increased during the 30 hours of use. I had to remove one of the 10 ohm resistors (had been two) in the power supply to get the current up to 100mA.

Bizarre, I wonder if the current use on these varies with temperature and age. At least there may be an initial 'breakin' period. Perhaps an APC supply is essential to get a steady output? Someone else go measure the current use on a well used pointer as see if it's changed.

Anyway, I carefully metered the current up to 100mA, and left it on for a few minutes with the DMM attached. It seems stable there. I'm now going to burn in the laser at 100mA. I'm planning on giving it 100 hours of use (which is only four days), a good burn in. When finished I'll measure the current use again and if it's changed.

I'm very happy with the pointer at 100mA - it's noticeably brighter and more powerful compared to 90mA, as 90mA was compared to 80mA. The beam is now clearly visible, even in a dim room - my eyes don't have to be dark adapted to see it. The laser now quickly stings my skin, and will light unsharpied wooden safety matches with ease. At 80mA it took a few seconds to pop a balloon at six feet - now the balloon dies instantly. I will not be increasing the power again. I'll let the rest of the whippersnappers try to determine a safe upper limit for these diodes.

Here are few videos of the brick, now at 100mA (likely between 80-100mW output)..

Lighting a wooden safety match
http://www.youtube.com/watch?v=6qdePtha0kg

Popping a balloon:
http://www.youtube.com/watch?v=TuhtS9Dalzc

Note how much longer the pointer took to pop balloon when it was running at 80mA:
http://www.youtube.com/watch?v=rfQJaTckSYs

Update this again in a week or two, after 100 hours use

 

[rkcstr]

Bizarre, I wonder if the current use on these varies with temperature and age. At least there may be an initial 'breakin' period. Perhaps an APC supply is essential to get a steady output? Someone else go measure the current use on a well used pointer as see if it's changed.

If you're using the LM317 in current regulation configuration, the internal resistance of the diode won't make any difference aside from changing the operating voltage.  

Did you measure the total resistance of your Rshunt (ie across the adj and output pins of the regulator)?  I'm thinking that running the pot at long periods of time (remember the full output current is going thru the resistors) may have increased the buildup of oxides on the contacts of your rheostat, causing increased resistance and thus decreased current.  But, that's just a theory since the current output should remain constant despite the resistance or voltage from the output to ground, provided you input high enough voltage to overcome the needs of the regulator itself in addition to the output voltage.

 

[climbak]

My professor told me today that the long term diode is now at 130mA, still going strong, still no heatsinking.

 

[flogged]

If you're using the LM317 in current regulation configuration, the internal resistance of the diode won't make any difference aside from changing the operating voltage.

Did you measure the total resistance of your Rshunt (ie across the adj and output pins of the regulator)? I'm thinking that running the pot at long periods of time (remember the full output current is going thru the resistors) may have increased the buildup of oxides on the contacts of your rheostat, causing increased resistance and thus decreased current. But, that's just a theory since the current output should remain constant despite the resistance or voltage from the output to ground, provided you input high enough voltage to overcome the needs of the regulator itself in addition to the output voltage.

No I never measured the resistance. You may be correct about the rheostat. However it's a large 3 watt rheostat - I should hope it can handle the current w/out oxidation.

I'll measure current use after another 50-100 hours.

It runs noticeably warmer @100 mA , compared to 90.

 

[rkcstr]

No I never measured the resistance. You may be correct about the rheostat. However it's a large 3 watt rheostat - I should hope it can handle the current w/out oxidation.

It was just a theory... not sure if it actually has any credibility  ;D  But, it was the only thing I could think of for why the output current would change despite not adjusting the rheostat.  You could try (when it's NOT powered) just turning it back and forth a few times to try to break up any build-up... this commonly happens in the volume knobs of audio amplifiers when they're left on the same setting for a long time, so I wouldn't be surprised if it happens in our case as well.  This was one reason I decided to go with sealed pots on my drivers, to help prevent oxide/debris build-up on the track/contacts.

 

[brtaman]

My professor told me today that the long term diode is now at 130mA, still going strong, still no heatsinking.

Wow, just when you think that these diodes can't get any better..:O How long has it been now climbak?

thanks for the great info!

brtaman

 

[flogged]

[
It was just a theory... not sure if it actually has any credibility ;D But, it was the only thing I could think of for why the output current would change despite not adjusting the rheostat. You could try (when it's NOT powered) just turning it back and forth a few times to try to break up any build-up... this commonly happens in the volume knobs of audio amplifiers when they're left on the same setting for a long time, so I wouldn't be surprised if it happens in our case as well. This was one reason I decided to go with sealed pots on my drivers, to help prevent oxide/debris build-up on the track/contacts.

Thanks for the advice. It was something I wasn't aware of. I can imagine a little drift in the rheostat's resistance, but it's drifted a lot (assuming this is the problem). My initial marking on the pot drove the LD at 82.5mA.. when I checked last night, after 35 hours use, I was only getting ~45mA from the same spot on the pot. I did try turning it back and forth a few times when adjusting the current.

If the problem persists I'll get rid of the pot and go back to a fixed resistor design, now that I know I'm going to keep the current at 100mA.

 

[rkcstr]

Thanks for the advice. It was something I wasn't aware of. I can imagine a little drift in the rheostat's resistance, but it's drifted a lot (assuming this is the problem). My initial marking on the pot  drove the LD at 82.5mA.. when I checked last night, after 35 hours use, I was only getting ~45mA from the same spot on the pot. I did try turning it back and forth a few times when adjusting the current.

If you're worried about resistance decreasing, that shouldn't be a concern.  If anything, the resistance will increase (meaning output current will decrease) with any sort of build-up on the contacts.  But, again, this is all speculation for you case.  The best bet would be to measure the resistance of the pot when you set it and after your "run" to see any changes.

Also, did you leave one of the terminals unconnected?  Ie pin 1 and 2 as the 'variable resistor', but 3 left open?  If so connect pin 2 and pin 3 (the wiper and the unused end of the track), as this will help to negate any change in resistance due to a "dirty" track.

 

[climbak]

Wow, just when you think that these diodes can't get any better..:O How long has it been now climbak?

thanks for the great info!

brtaman

It's been running since may 5th at about 2pm Arizona time, so in 3 hours from now it will have been running for 1200 hours.

 

[brtaman]

*woot* You just made me extremely happy! I think its time for a victory jig!

90ma was the minimum IIRC, and then 100 for a short time and now 130...these diodes can take soo much more current then I thought, time to start scavenging the web, must create a stock pile, just in case.

Thanks
brtaman

 

[flogged]

If you're worried about resistance decreasing, that shouldn't be a concern. If anything, the resistance will increase (meaning output current will decrease) with any sort of build-up on the contacts. But, again, this is all speculation for you case. The best bet would be to measure the resistance of the pot when you set it and after your "run" to see any changes.

Also, did you leave one of the terminals unconnected? Ie pin 1 and 2 as the 'variable resistor', but 3 left open? If so connect pin 2 and pin 3 (the wiper and the unused end of the track), as this will help to negate any change in resistance due to a "dirty" track.

I had connected pins 2&3, so that wasn't the problem. Now that I think about it you're correct - it would seem the rheostat's internal resistance has been increasing. Ug. Annoying. So I got out the soldering iron and my trusty old analog multimeter. I bypassed the pot. Using a fixed 14 ohms of resistance gives me exactly 100mA of current use. Hopefully I wont have anymore problems with current drift now.

After I've put some mileage on the diode I'll measure it again - if the current does continue to drift the rheostat was not the problem.

At 100mA this thing is BRIGHT and it BURNS with more authority than my 125mW red. Crazy at night.

 

[climbak]

I've got mine running at 150mA. It's putting out somewhere between 160 and 190 mW. I need to send it to someone with a thermal meter for a confirmation.

 

[ndrew2505]

i was just wondering has anybody taken apart a toshiba sd-s802a? google says its an hd drive like the sd-h082a.

 

[Kenom]

climbak if you want I'd be happy to verify your lasers output. I have several thermal meters.

 

[climbak]

thanks kenom. I'm gonna kill the batteries that are in it right now and then probably send it to one of you thermal meter owners. Gotta play some more before I have to go without for a week.