January 10, 2011
about 4 years ago
I just received this part and noticed that it produced a nice bright “spot” at only 15 mA. Much less than the data sheet’s nominal current of 35 mA. I made some measurements of the V-I curve that other’s might find helpful. The measurements can be found at “http://www.nbnis.net/info/wentaiLaserCardVIchart.pdf”.
Based on these measurements it appears that the laser should be operated around 15mA to 20mA, not 35mA. Because the laser has a built in resistance this corresponds to 3-7 Volts applied to the laser. This means the laser can be connected directly to a LiPo battery with out any other components. I’ve tested this and it works as expected. The only issue that still needs addressed is how to keep the laser from discharging the LiPo battery to less than 2.75V. Putting a silicon diode (forward biased) in series with the laser should prevent the battery from discharging below 2.9V (2.3V laser diode + .6V silicon diode). This makes for a very simple circuit (laser+diode+battery) that will reliably operate the laser from battery power. BTW.. the red lead is the positive lead. (Not shown on the part’s drawing.)
If anyone sees a flaw in this approach please point it out.
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