short die open can dies at 250mA. alas

[adgmeijin]

phenol what would you suggest, im building a new smaller version of DDL driver without trimpot , only 3 ohm 1/2W, do you think it can give me good mA and good mW with that set up? please, im just refreshing everything thanks.

 

[cybob101]

phenol are you sure that a dead diode has the same load specs as a live one?

 

[adgmeijin]

phenol heres the driver i made, its actualy double sided pcb i used here, and the switch, apologise for the image quality

 

[phenol]

i dont know what your input voltage is, but you may want to mount a small heatsink on the LM317. According to Dr Lava's VIP curve of the long -die open can, at that current it should put out in excess of 250mW. Also pay attention to diode heatsinking! If it feels hot, and even warm, to the touch, it is already too hot. Im not really planning on pushing any of mine above 350mA, and never have even briefly, so I have no experience in hard overdriving. Has anyone here had their open can still lasing ok above 400mA?

 

[phenol]

phenol are you sure that a dead diode has the same load specs as a live one?

well, if its mirror facets are the only damaged thing and the junction is intact, it should still be a diode from an electrical point of view. if the junction is fried as well....it's just a piece of rubbish really.

 

[adgmeijin]

actually im using 2 pcs 3.6v RCR123a, so what would you recommend to have lower than 350mA, will i need to use the Trimpot? please give me specifice resistor value together with my 100 ohm trimpot thanks.

 

[phenol]

first of all - can your trim pot handle such current and dissipate such power? just pick a happy current and use a fixed resistor, keeping ur design even tinier. for 350mA you need 3.57ohms. use a standard 5% 3.6ohm 0.5W resistor

 

[adgmeijin]

so you mean its fine with the driver without trimpot as long as i get the right value of resistor?

 

[phenol]

it is fine, if not even better. i dont trust pots

 

[adgmeijin]

phenol do you think it doesnt need adjustment from high resistance to low before i will run the LD normally, cuz im worried for bumping of the current at once instead of slowing up the output adjustment, do it ok, for that LD?

 

[chido]

hey chido is it ok if i use 1/2 w 3 ohm resistor in my ddl driver to run my LG 20x dvd LD, do i need to secure the heatsink to run it well? i think i fail to secure the heatsink :-/ thats why i killed my red laser last time...

A 3 ohm resistor should give you 416mA which equals .520 watts, I would just use a 1 watt resistor but I think you should can get away with a 1/2 watt.
And what do you mean by securing the heatsink? It has to be tight against the aixiz module if you want it to be efficient and dissipate heat.

 

[adgmeijin]

cuz i found out that the when i resolder on my driver , the LD and heatsink bumped on something then accidentally puts out the LD from the heatsink and took it back, when i test it , it puts out the light then dies...1/2 3ohm resistor was fine with the driver for my LD or do i need 1 w type one?

 

[chido]

Ok, if you bumped your laser, then it's possible the diode got damaged and that's why it died, but when you say your LD came out do you mean the laser diode, or the complete aixiz module came out of the heatsink?
And like I said, you should be fine by using a 1/2 watt resistor.

 

[adgmeijin]

ok thanks, do i need to put an Arctic thermal paste or epoxy on the heatsink? so i can manage to run my LD with DDL driver using the 3ohm 1/2w resistor.

 

[chido]

You don't have to use thermal paste if your aixiz module has a tight fit on the heatsink, if it doesn't, then you should use it.

 

[jayrob]

Chido sent a short open can for testing, and here are some results.  It could not achieve the same output as the long die open can, it hit the knee at about 350mA and 200mW.  The plastic lens had the rear aperture opened to allow for higher power.

Another great graph drlava. Thanks for your work.

This graph confirms what I have found with my comparisons between the AixiZ acrylic lenses (plastic cut away) vs the AixiZ glass lenses. Not much difference in power. The Meredith glass lens on the other hand, gives about 20% more power with the open can reds, and about 30% more with the blu-rays. (compared with 'cut away' AixiZ acrylic lenses, or Meredith acrylc lenses)

The Meredith glass lens is an single element lens, but the main difference, is it's design. It is a 'short focus' lens. Meaning that it must be mounted very close to the LD, in order to get focus. See this diagram:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1207011306/36#36
Jay