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I recently took apart 2 DVD readers? Might have been burners too, but my question is why can't I see the lasers? I tried using both 2 and 4 AA batteries hooked up according to this diagram http://d13z1xw8270sfc.cloudfront.net/origin/58770/diode_wiring_diagram.jpg . I can feel the diode heating up after about 5 seconds, but I can't see the actual laser. Thanks for the help.

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  • \$\begingroup\$ connecting the diode with 2 or 4 AA battery without resistor would very likely destroy the diode \$\endgroup\$ – Oka Aug 26 '15 at 1:11
  • \$\begingroup\$ Oh crap, what's the correct voltage to use then? All the youtube videos I saw had them use 2 AA batteries \$\endgroup\$ – nadjatee1996 Aug 26 '15 at 1:25
  • \$\begingroup\$ Not sure, maybe vary, from this danyk.cz/laser3_en.html tutorial it stated: "The voltage drop of infrared laser diode is 2.15 V and the voltage drop of red one is 2.5 V". If you are using higher voltage, you should use current limiting resistor or current regulator \$\endgroup\$ – Oka Aug 26 '15 at 1:37
  • \$\begingroup\$ If you did happen to light the laser diode and shined it into your eye you may have damaged your eye to the point of not being able to see it!! \$\endgroup\$ – Michael Karas Aug 26 '15 at 3:22
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    \$\begingroup\$ Which is why, in some circles, a tshirt is often referred to which says, "Do not look into laser beam with remaining good eye." \$\endgroup\$ – WhatRoughBeast Aug 26 '15 at 3:57
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I don't have the rep to comment, but it sounds like the answer to your question is that the diode may be working and you can't see the light because infrared is outside of the visible spectrum.

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  • \$\begingroup\$ why would you need a rep to comment? If you think you know the answer \$\endgroup\$ – Bruce Aug 26 '15 at 20:27
  • \$\begingroup\$ CD-only readers used IR lasers. DVD readers need a shorter wavelength--visible red, I think. BluRay should be self-explanatory. \$\endgroup\$ – Solomon Slow Aug 26 '15 at 20:47
  • \$\begingroup\$ Ah, that explains a lot. Last question is it normal for those IR lasers emit a lot of heat? \$\endgroup\$ – nadjatee1996 Aug 26 '15 at 21:59
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There are lasers with all kinds of wavelengths. Only a small part of the EM (electromagnetic) spectrum is visible light. So it's possible it is in the infra red range. You can often see IR light with a digital camera. Also never look directly into the laser also invisible light can burn or harm your eyes. visible light spectrum

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