Minty Green 20mw 515nm Laserbtb Pointer

[AMooMooCow]

I had been geeking out about these laser diodes since they were first introduced on the market. When I got the item today, I was a little disappointed that it wasn't much noticeably different from my 532nm pointer. But that was in broad daylight. There's something about this wavelength that makes it look incredibly mint-green during dim lighting conditions. Probably something to do with over-saturation of the cones during the day in conjunction with the activation of rhodopsin during low light.
Worth it? So much.

you may fire when ready

This is the most accurate description of the color I can show since RGB monitors can't reproduce it. But it's still completely off from what it really is.

I like to run it on 1.2v rechargeable AAAs since it's easier to look at at a lower power. ---Edit: false assumption.
Construction is nice. The button doesn't jiggle around.
The problem where the diode runs at very low amperage when the laser is armed Thread is still there, but on 1.2v batteries the driver seems to be completely off. Never look into a laser diode, kids, I did it with my phone camera.

Edit: I've installed 1.2v NiMH batteries and left the laser armed for weeks and it has not seemed to have drained the batteries. Then I reinstalled 1.5v batteries and found it to not exhibit the behavior. I cannot confirm it's running at 0.000Amps though as I have no measurement device for that.

 

[Cyparagon]

I like to run it on 1.2v rechargeable AAs since it's easier to look at at a lower power.

Does it use a constant current driver, or doesn't it? Have you measured the power with different cells, or is that a guess?

 

[AMooMooCow]

Does it use a constant current driver, or doesn't it? Have you measured the power with different cells, or is that a guess?

I was just assuming it's a boost driver since Vf is like 6v, where the current supplied by a boost driver is highly dependent on the input voltage

 

[mortuus]

there is a difference on the 515 and 520 compared to 532, to me when i have both 520 and 532 the 532 to me looks more lime green and the other pure green also called forest green.

 

[AMooMooCow]

Does it use a constant current driver, or doesn't it? Have you measured the power with different cells, or is that a guess?

Update: measured the current pulled from the 1.5v batteries as voltage over a 1 ohm resistor. Results are inconclusive. The driver seemed to start pulling more and more current to compensate for the resistor. It started at 340mA and climbed to 420mA where it started making a whining sound and dropped the current back to 340mA where it started to fall.

Is that what a constant current driver does? I've never had a driver smart enough to do that.

 

[Cyparagon]

Yep, that's a constant current driver. The battery voltage drops as it drains, so the driver pulls more current to compensate and keep output current constant. There's a lower voltage limit, or course, which depends on the design specifics. I doubt using NiMH has any effect on power compared with alkaline cells.

 

[AMooMooCow]

Nice. All the chinese drivers I ever used had serious differences in output amperage from a difference of input voltage of only 0.4v. This laser is turning out much nicer than I could have made myself. Very pleased.

 

[Pman]

I'll take 515/520 over 532nm everytime. Like most of us have found, you don't realize the difference until you see them side by side like the 445/450 compared to 462nm (which according to DTR testing is 464nm for the M462. The 520 and 462 are more "pure" when you say you have a green and blue laser. Congrats

 

[AMooMooCow]

I just got an LPM a couple days ago. Yes, I was completely wrong about the 1.2v batteries.

I went to 4:30ish minutes, but it was getting pretty warm so I stopped. 38.1mW max. Seems to exhibit a form of thermal runaway. You can tell that it wants to be 25mw, but as its temperature increases it puts out more power. Since laser diodes tend to put out less power when they get hot, it's due to the driver.

Here's the long version of reading this power graph (with audio):

 

[FiveTwentyThreeHundredmW]

Minty as in: slightly, SLIGHTLY more towards blue, it's a cooler (temperature-wise) color. Cooler, fresher, sublime. I heard a member here call 532 an "acidic"/hot green...I think that's a great way to say it. 532 is so green it almost feels unnatural and even irritating sometimes. I still like 532 but don't like the IR and temperature sensitivity. I'm planning to buy a 520nm soon. Maybe the Sci Fi 200-300mW... :drool:

It's awesome to see this in a pen pointer. Very unique. I didn't know they had 515nm, I thought only 520nm. Never seen either but I'm sure the camera doesn't do it justice. I've heard they peak eye sensitivity daytime is ~555nm, darkness it's ~505nm...hmmm.

340mA seems high? Is 515/520 a less efficient diode, or simply requires more power in general? I've had an AAA 30mW 650nm which only took about 150mA. Roughly same for my 16340 100mW 445nm.

 

[AMooMooCow]

340mA seems high? Is 515/520 a less efficient diode, or simply requires more power in general? I've had an AAA 30mW 650nm which only took about 150mA. Roughly same for my 16340 100mW 445nm.

Actually, the Osram PL-series diodes are only 4.6% efficient at 100mA (28mW [DTR]), but I measured 340mA from an ammeter connecting the batteries to the body. That usually works when measuring laser pointer current pull, but this one acts funky, like it works on some sort of logic circuit that wants to even out the power loss from the 1-ohm ammeter, so it applies more and more current and I couldn't get a discrete reading. The applied current is also influenced by temperature in this laser as observed when I made the power graph.