Re: Group buy for 16X dvd burner diodes !

[Gazoo]

Re: Group buy for 16X dvd burner diodes !

Hey Daedal,
The only problem is now we are going to have to figure out a name for your new circuit.. ;D Looking forward to it.

You have more guts than I do. I really wonder what the power output of the diode was when you pushed 600ma. through it.

I received my diodes today, but unfortunately I still need to get a decent trim pot for the circuit. But I can't wait so I will do some experimenting and report back with some results.

SenKat,
Thank you for putting this deal together for us, and for your care in packaging my diodes

 

[Gazoo]

Re: Group buy for 16X dvd burner diodes !

Here's a sorta quick update on what I have experienced with the diode. First of all, I am using the LM317 as a voltage regulator only because I don't have a decent enough trim pot to use it as a current regulator. I am accomplishing the same thing. By adjusting voltage to the diode, I am also adjusting current. More voltage = more current.

I will tell ya these diodes are worth every penny. I have pretty much abused it and it is still ticking. I have run it as high as 500ma, then quickly backed off. This was with no cooling. I have not had similar results with other diodes, usually they went "poof" above 350ma. So I can conclude these diodes are tough.

I have it mounted in the smaller of the Aixiz modules, the little brass one. I am using my vice to hold it so it is getting plenty of heat sinking. I haven't been able to test much long range burning yet. But at 16", it will light a safety match easily. No sharpie needed. This was with 160ma applied to the diode. I was also able to light a light gray headed match, but it is tricky. The trick is to aim for the base of the head of the match, this is what works best for me. As far as the red headed safety match goes, there are no tricks. They light instantly.

Recommendations and common sense are basic. Don't apply more current then you need to be satisfied. I am finding 160ma is working out well for me, but of course we all want more power. Since I have 5 diodes I can risk blowing a couple, and I will be ordering 5 more soon. Keep the module cool. Additional heat sinking is a must if you plan to run it for more than a minute at a time. If possible, use Daedal's circuit. It is very stable.

Last but most important, use safety goggles especially when burning up close.

 

[chimo]

Re: Group buy for 16X dvd burner diodes !

Here's a sorta quick update on what I have experienced with the diode. First of all, I am using the LM317 as a voltage regulator only because I don't have a decent enough trim pot to use it as a current regulator. I am accomplishing the same thing. By adjusting voltage to the diode, I am also adjusting current. More voltage = more current.

What you have to keep in mind is that the current through the diode is not only dependant on the voltage applied but also its temperature. That same voltage that resulted in a LD current of 350mA when the diode was cold, may result in enough current to fry it when it heats up.

If you drove it with a current source, the voltage will fluctuate, however, this fluctuation will be harmless because the current is fixed.

Driving an LED or LD with a voltage source is generally not advised and should only be considered as a last resort.

Good luck on your mods.

Paul

 

[Gazoo]

Re: Group buy for 16X dvd burner diodes !

Paul,
Would you mind explaining to me why it is better to regulate current to the diode as opposed to regulating voltage? I really am having a difficult time understanding this. I have done both and have not noticed any variations in either voltage or current. If one is applying 3 volts regulated to a diode, why would the current fluctuate? Conversely, if one is applying 200ma regulated to the diode, why would the voltage fluctuate? I would appreciate an explanation.

And about the diodes. Both diodes were cool when I applied high current to them.

So far, from my limited knowledge with laser diodes, I like these diodes better than the others I have tried, and these have been much less costly than any other diodes I have tried.

I have a different one still going strong that I like the looks of better, an open can diode. I am pushing a regulated 240mw into it. I find it to be an amusing little jewel. It came out of a 20X DVD burner and this is the only place I know of to get them from. So I am not going to push that one with any more current.

 

[Hemlock_Mike]

Re: Group buy for 16X dvd burner diodes !

Gazoo --

This is why I keep saying " DO THE MATH" !!! The resistance (V/I) is not linear at the top end. If you slowly increase I and read V over a lasing range and graph the data, you will see a critical curve. At the top end, a small increase in V will cause a large increase in I. That's why we talk about I (current). That's also why we use a current source with the LM317 as DDL has tried to explain.

Mike

 

[Daedal]

Re: Group buy for 16X dvd burner diodes !

+1 on Mike's explanation. The LD acts as a load in this circuit. When you are supplying regulated current and unregulated voltage, the diode takes what it needs to lase and the rest is dissipated into ambient heat (out into the environment -- useless). With the circuit that I have made, I tried to keep the voltage a little higher than what is needed for the worst case scenario.

[EDIT] Through some stroke of stupidity I rambled about something that is completely false and when I wake up tomorrow I will try to explain it again without all the errors. Thank you for pointing that out Gazoo [/EDIT]

I say it again... Unregulated current into a diode of any kind, LED or LD, is just a death wish. When using the LM317 as a voltage regulator the current is capped at 1.5 Amps on average... 1.5A will fry a 500mW CW diode! These are rated 80mW CW. You can do the math now...

Current is not a function of voltage in these situations, it's only a function of the load, which is a variable. When you control the current, the variable is the voltage. With a 6V supply, even if the voltage jumps up to 6V all the way, the diode will be fine. But when letting the amps fly through uncontrolled by anything other than the laser diode, the voltage you supply is nothing but what voltage you want to fry the LD at... ;D Try and connect a DMM to your 2 x CR123A setup and check out how much current you get through... depending on your batteries and DMM, they might kill your DMM!!

I believe you have the choice to do as you please. I am simply doing everyone else a favor here by trying to keep their LD's alive. Please, by all means, if you feel that that is how you want to run your LD, that is ok. But advising people to do it is not very nice. It is simply a matter of luck that is keeping that diode alive for as long as it stays alive, and I'm sorry to say that...

GL all, and be safe;
DDL

 

[vathink]

Re: Group buy for 16X dvd burner diodes !

+1 on Mike's explanation. The LD acts as a load in this circuit. When you are supplying regulated current and unregulated voltage, the diode takes what it needs to lase and the rest is dissipated into ambient heat (out into the environment -- useless). With the circuit that I have made, I tried to keep the voltage a little higher than what is needed for the worst case scenario.

Now, when you regulate voltage as you suggest... here is what happens. You have obviously seen pictures of the inside of a laser diode. It is a VERY thin wire that connects the diode leads to the lasing dye. If the wire is at room temperature then it would have a MUCH higher resistance than it would at, say, 70 Degrees Celsius. 70 degrees Celsius is a very common temperature inside a diode... INSIDE, not outside. You have to take everything into account now. With the wire getting hot, the resistance is EXPONENTIALLY dropping... lower resistance means higher current. The more current there is going through a tiny wire, the more heat is being generated... it's a domino effect that you CANNOT stop if the current is not regulated.

I say it again... Unregulated current into a diode of any kind, LED or LD, is just a death wish. When using the LM317 as a voltage regulator the current is capped at 1.5 Amps on average... 1.5A will fry a 500mW CW diode! These are rated 80mW CW. You can do the math now...

Current is not a function of voltage in these situations, it's only a function of the load, which is a variable. When you control the current, the variable is the voltage. With a 6V supply, even if the voltage jumps up to 6V all the way, the diode will be fine. But when letting the amps fly through uncontrolled by anything other than the laser diode, the voltage you supply is nothing but what voltage you want to fry the LD at... ;D Try and connect a DMM to your 2 x CR123A setup and check out how much current you get through... depending on your batteries and DMM, they might kill your DMM!!

I believe you have the choice to do as you please. I am simply doing everyone else a favor here by trying to keep their LD's alive. Please, by all means, if you feel that that is how you want to run your LD, that is ok. But advising people to do it is not very nice. It is simply a matter of luck that is keeping that diode alive for as long as it stays alive, and I'm sorry to say that...

GL all, and be safe;
DDL

Care to point out where about is your circuit mate? Is it in this thread? Cheers mate.

 

[Daedal]

Re: Group buy for 16X dvd burner diodes !

Sure thing

http://www.laserpointerforums.com/forums/YaBB.pl?num=1185701612

--DDL

 

[Daedal]

Re: Group buy for 16X dvd burner diodes !

Ok, here's a slight explanation for what happens when the current is sent too high into a diode...

http://en.wikipedia.org/wiki/Catastrophic_optical_damage

--DDL

 

[Gazoo]

Re: Group buy for 16X dvd burner diodes !

Daedal,
I would like to publicly thank you for your lengthy PM reply back to me, and taking the time needed to get it through my thick skull. It is beginning to make sense why current regulation is a must.

The LM317 voltage regulator circuit I am using is being powered by one of those Radio Shack 12 volt adapters that plugs into a cigarette lighter. I have it plugged into a power pack and have the voltage set at 6 volts. Also please note it is a switching adapter, and as I recall it can supply over an amp. However as you know switching adapters are very precise voltage sources. Perhaps this is why the diode has lasted as long as it has.

I think my open can diode is current regulated. The reason I think this is because I am using a driver board that came out of another laser module. This is powered by four nimh batteries and the current stays constant until the voltage of the battery pack drops. I think it is around 4.5 volts when the current begins to drop. I was using this driver board with another diode and it lasted over a month. The only reason it didn't last longer is because the positive leg on the diode came loose. Yes, this was another lesson learned...lol.

For everyone else: I am definitely not implying, advocating, or suggesting under any circumstances that anyone use the LMT317 as a voltage regulator to power a laser diode. I have always said in my posts to use Daedal's circuit. As I previously stated, the only reason I am using it as a voltage regulator is because I don't have the trim pot I need to use Daedal's circuit properly. I wanted to whip up something I could use to vary power to the diode so I could see the different effects without having to swap out resistors, which is what I had to do with Daedal's circuit. Once I get decent trim pots, I can begin to use Daedal's circuit just as he designed it.

 

[wizcam]

Re: Group buy for 16X dvd burner diodes !

Daedal, are you by any chance going to make and sell your circuit?


Stan

 

[wizcam]

Re: Group buy for 16X dvd burner diodes !

I was wondering, would it be possible to use the diodes we just bought to replace the diode in the "GlowTorch" from the GB, in case it should burn out? :-/


Stan

 

[SenKat]

Re: Group buy for 16X dvd burner diodes !

Possible ? Yes !
Difficult ? Yes !

Although some of them came apart during shipping - they did not come apart where it would be easy to remove the diode ! These things are built rather well - with the exception being what was already mentioned - the brass ring in the middle can be too large seomtimes.

 

[Daedal]

Re: Group buy for 16X dvd burner diodes !

Daedal, are you by any chance going to make and sell your circuit?


Stan

Well... I am trying to see how I can make the whole circuit fit inside a small aluminum enclosure that holds the circuit for a 5W flashlight. Make it yes, sell it... I don't think so. I'll just leave the building work to you guys. It's more fun like that

--DDL

 

[Gazoo]

Re: Group buy for 16X dvd burner diodes !

Is this going to be a boost/buck circuit? I am very curious. The ideal circuit would be adjustable, and be able to maintain a set current. So if for example, I wanted to set the current to 200ma, the circuit would be able to maintain this over a voltage range of 2 volts to 4 volts. Like the boost/buck LED driver circuits are capable of.

 

[wizcam]

Re: Group buy for 16X dvd burner diodes !

They have a Cheap 5W Led Flashlight at Dealextreme for $4.88

http://www.dealextreme.com/details.dx/sku.4779

Stan