IR Diode from DVD

[Hemlock Mike]

I am trying an IR diode from a DVD in a holder. It works but how do you check the focus ?? I'm using a digital camera and it doesn't focus on the spot very well. I can see it smoke the paper but I can't tell when it is sharp.
Also what wavelength are these diodes??
Has anyone tried these ?? How much mA do they take ??

Mike

 

[Hemlock Mike]

Wellllll ---

I'm up to 300 mA and can burn black paper at 3' and pop balloons.

It's damn hard to adjust focus wearing OD6 goggles, hold digital camera and turn focus ring !!

It appears that IR is more critical on focus with a shorter depth of field for heat. It's just hard to get it to a point.

Anyone know the nM and max mA ??

Mike

 

[PhotonWrangler]

CD drives use 780nm NIR diodes; DVD optical pickups use visible red.

 

[Hemlock Mike]

Thank you--


I now have a small piece of the puzzle. I can see a very dim Very dark red spot if I take a glance at the spot. It's running good at 300 mA.

I haven't taken a power reading yet.

Mike

 

[dr_lava]

Is this from a DVD/CD writer combo drive? At that current, I'd guess about 200mW.

 

[Hemlock Mike]

Dr -

I'm guessing that too -- Now I have to calibrate my beam splitter with something known !! I'm guessing it will go higher because the beam seems stable and little heating. Junction voltage is 2.55. Cuts black paper and rips balloons if focused.
I sure don't like the goggles but so be it.....

Mike

 

[PhotonWrangler]

Thank you--

I now have a small piece of the puzzle. I can see a very dim Very dark red spot if I take a glance at the spot. It's running good at 300 mA.
Mike

Bingo. A 780nm diode produces a very dim, deep cherry red spot, just like you described. My guess is that it's one of Sharp's LT022 series.

 

[kdam36]

never ever look directly into the diode when its powered up as you cant see the energy it emits and you WILL DAMAGE YOUR EYES !!!!....

 

[532nm]

In response to the original posted question- if you have a night vision scope or NV goggles maybe that would work; or use any cheap 'board' camera; B&W works best or remove the IR filter from a color camera. There are some available for as little as $9 (+you'd need to plug it into a TV)

 

[dr_lava]

Another idea is to pulse the laser for 10 sec. or so at different focus settings (if your lens setup is screw focus?) and look at the burn dot size.

 

[David_Web]

Hope it's on topic.
How strong would a CD-RW ir-laser be? Or do I need to have a dvd-rw to get useable power.
btw I am thinking if a CNC type of thing for plastic/paper or other stuff

how about a laser from a printer.

200mW sounds like a LOT when properly focused down to 0.01mm

*edit* maybe I should make my own topic

 

[Hemlock Mike]

I NEVER look nown the bore of any gun !!! I have laser defence goggles OD6 to protect against scattering. I also built a flash pumped NdYAG laser about 20 years ago and still have my eyes

I was burning pin holes in black paper last night so it must be focused - at least at 4'. Move the paper to get a really fine cut.

Mike

 

[PhotonWrangler]

Hope it's on topic.
How strong would a CD-RW ir-laser be?

30 to 60 milliwatts

how about a laser from a printer.

5mw. Those Sharp LT022 780nm 5mw diodes are popular in laser printers. They don't need to heat anything; they just have to discharge a photosensitive surface on the drum.

 

[Hemlock Mike]

WWwweeellllll -- The ground clip popped off tonight and when I reconnected it, the current shot to 340mA :-( No more laser............

Dr_Lava's use of a capacitor may be a good idea here !!! I sure can't explain it because it was running at 290 mA cool.

Mike

 

[PhotonWrangler]

It takes just a sub-millisecond spike to shatter something in the laser cavity. I've accidentally blown several laser diodes from glitching them while they were operating. In one case the case ground became slightly intermittent and then poof! It suddenly went from laser to low-powered LED.

 

[Hemlock Mike]

From now on, I'm putting a small tantalum capacitor across the diode to soak up crap !!

Mike

 

[Hemlock Mike]

I found some small 1 mfd tantalum caps in my junk box.

Dr_Lava ,,,,, How big is the capacitor you are using? I figure a 1 mfd will lower the impediance enough to prevent damage.

Mike

 

[dr_lava]

I did some modeling and decided to go with a 100uF 6.3V cap to go with the 2.7 Ohm resistor. This is probably 100x more than needed, but who knows *what* people will try to do with these things and I wanted to be the safest possible. A 1 uF would have had a time constant of 2.7us, still well above the 50-100ns switching speed of the diodes.