Old 04-16-2010, 06:44 PM #1
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Default Assessing some unknown lasers

I am a total laser noob so please be kind! I will be reading a bunch more on this site to improve my knowledge, but I thought I would throw a question up to hopefully get some advice. I was recently in China and picked up three green lasers, two marked as 200mw and one marked as 300mw. They are total knockoff/noname/whatever units and I bought all three for about $70 USD but I was hoping to find out more about their true specs and if they are hackable, since I have some electrical/electronics background and generally like to tinker.

The 300mw unit has a much larger diode assembly (and a much larger battery, not sure what type but it's about the size of two CR123's stacked), so I think it's stronger but the beam doesn't look much brighter than the 200mw units (that use CR123 batts). Also, the sticker on the 300mw unit is in red, and the other two stickers are in green so I think it may have been mis-labeled. Of the 200mw units, one looks a bit brighter than the other but it appears that it is just scattering more light; when I shine it at a wall it makes a faint green cloud around the point for a good 15 or 20 degrees away from center. So, they are probably pretty close aside from this difference.

Is there any good way to benchmark their power without a genuine measuring tool? Maybe making a test stand with a target of thin black plastic, and seeing how long it takes for each to burn a hole clear through it? Also, is it OK if I put up a few pics of the pointers and the diode assemblies for advice from the crew? Finally, there any other noob-grade observations you guys can share? I am open to all information. Thanks!


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Old 04-16-2010, 06:53 PM #2
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Default Re: Assessing some unknown lasers

A Laser Power Meter is the only way to tell. Many of the veterans here will measure your lasers for you for the cost of shipping

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dave
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Old 04-16-2010, 07:00 PM #3
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Default Re: Assessing some unknown lasers

Thanks for the suggestion, I may consider it but I dunno if these lasers are worth the bother since they are so cheap. The initial $70 was hard enough to explain to my wife! Also, half the fun of tinkering (for me at least) is designing an experiment and following it through to a measured result. I bought these just for the fun of it, after all.
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Old 04-16-2010, 07:02 PM #4
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Default Re: Assessing some unknown lasers

Quote:
Originally Posted by joebob2000 View Post
Thanks for the suggestion, I may consider it but I dunno if these lasers are worth the bother since they are so cheap. The initial $70 was hard enough to explain to my wife! Also, half the fun of tinkering (for me at least) is designing an experiment and following it through to a measured result. I bought these just for the fun of it, after all.
Cool! If you do not worry about how many mW they are putting out, you can enjoy them just for the light they give. No meter needed for that

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Old 04-16-2010, 07:09 PM #5
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Default Re: Assessing some unknown lasers

Is there any benefit to measuring how much power they draw to operate, like is there a rule of thumb about efficiency I could use to guesstimate the light output? I have a few multimeters and some other DC test equipment, I may try benchmarking that. Is there a way to know the optimal voltage these lasers operate at or should I just match the output of the battery they are equipped with? Each laser has a small PCB with a trim pot, an IC and some other components so I don't know if this is a buck/boost regulator that would be accepting of a variety of voltages, or just part of the normal powertrain of a laser that needs a specific voltage for the best operation.
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Old 04-16-2010, 07:27 PM #6
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Default Re: Assessing some unknown lasers

Quote:
Originally Posted by joebob2000 View Post
Is there any benefit to measuring how much power they draw to operate, like is there a rule of thumb about efficiency I could use to guesstimate the light output? I have a few multimeters and some other DC test equipment, I may try benchmarking that. Is there a way to know the optimal voltage these lasers operate at or should I just match the output of the battery they are equipped with? Each laser has a small PCB with a trim pot, an IC and some other components so I don't know if this is a buck/boost regulator that would be accepting of a variety of voltages, or just part of the normal powertrain of a laser that needs a specific voltage for the best operation.
Sorry. No. With DPSS modules, such as that in the green lasers you have, the crystal alignment and quality have too much influence on the output to be able to estimate output based on current. You can get a rough estimate of the output of the pump (IR) diode, but not the green output.

In a diode laser **IF** you know which diode it is, AND you know the lens, AND the diode has been graphed several time, THEN you can get a ROUGH estimate of output.

With a DPSS module, all bets are off

Most of the drivers in those lasers are linear. The IR pump diode only takes >3V. All drivers have parameters, but you would have to figure that out from the components

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dave
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Last edited by daguin; 04-16-2010 at 07:30 PM.
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Old 04-16-2010, 08:03 PM #7
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Default Re: Assessing some unknown lasers

Does the ceiling bounce test (the "eyeball" meter for flashlights) work the same with lasers? You could try that. in a dark room, shine it at a wall behind you or the ceiling if it is smooth, and see how bright the room gets. It's easier to see differences if you point the flashlights (or lasers) in the same place, out of your vision (i.e. behind you, above you, something like that)

Don't know how much of a difference you could see, but it's free
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Old 04-16-2010, 08:07 PM #8
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Default Re: Assessing some unknown lasers

Quote:
Originally Posted by BShanahan14rulz View Post
Does the ceiling bounce test (the "eyeball" meter for flashlights) work the same with lasers? You could try that. in a dark room, shine it at a wall behind you or the ceiling if it is smooth, and see how bright the room gets. It's easier to see differences if you point the flashlights (or lasers) in the same place, out of your vision (i.e. behind you, above you, something like that)

Don't know how much of a difference you could see, but it's free
I think he was hoping for more than "this one is brighter than that one."

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Old 04-17-2010, 04:16 PM #9
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Default Re: Assessing some unknown lasers

Here are pictures of the lasers, if anyone is interested! I am curious about the actual laser assemblies; all of the PCBs appear to have the same components on them, but on one of them (one of the two '200mw' units' that usually appears a bit dimmer) has a different design to the brass housing of the diode (its on the right of the last pic.) It adjusts just the lens with a tiny notch right around the lens, whereas the other two adjust by turning the entire foreword part of the assembly (as seen on the left of the last attached pic.)

I have noticed that as I take them apart and re-assemble them they sometimes don't work quite right (they are dim or won't light). I think it has to do with the case fitting together to provide the positive current path, as unscrewing and fiddling with the fittings seems to make it start working again. Is this a common problem with handheld lasers like this, and is there some good way to get them to go together consistently? Dielectric grease in the threads, maybe?
Attached Thumbnails
Assessing some unknown lasers-img_9425_sm.jpg   Assessing some unknown lasers-img_9434_sm.jpg   Assessing some unknown lasers-img_9435_sm.jpg   Assessing some unknown lasers-img_9442_closeup.jpg  
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Old 04-17-2010, 04:34 PM #10
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Default Re: Assessing some unknown lasers

MANY of them use the same IR pump diode so the driver is the same. The differences in output are the result of the aforementioned crystal alignment and quality issues. One of the major ways that modules are classified as to output is simply by final measurement. ALL of the modules are manufactured in exactly the same way using the same components. Then their output is meaured and they are "binned", priced, and sold based on that output measurement.

Sometimes they are turned down to allow for import into places like the UK and OZ

The crystals are VERY sensitive to alignment. If disassembly and re-assembly affects that alignment, the output may change.

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Old 04-17-2010, 05:03 PM #11
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Default Re: Assessing some unknown lasers

I didn't take apart the crystal assembly (one was loose so I turned it til it made a nice point and then glued it in place.) By reassembly I mean the aluminium shell that goes around the laser assembly, and the entire enclosure. I think the fittings just dont conduct well. I noticed on some of the handheld projects on this site a set screw is used, is this the only way to get a good electrical connection?
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Old 04-18-2010, 01:27 AM #12
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Default Re: Assessing some unknown lasers

Quote:
Originally Posted by BShanahan14rulz View Post
Does the ceiling bounce test (the "eyeball" meter for flashlights) work the same with lasers? You could try that. in a dark room, shine it at a wall behind you or the ceiling if it is smooth, and see how bright the room gets. It's easier to see differences if you point the flashlights (or lasers) in the same place, out of your vision (i.e. behind you, above you, something like that)

Don't know how much of a difference you could see, but it's free
After a bunch of screwing around, making sure the fittings were all tight and the laser lens was securely glued in place, each of the three is almost indistinguishable to the naked eye in terms of the visible beam path and the dot. However, in a very un-scientific test in a 100% dark room to see how much of the room gets lit up, I did confirm that the 'bigger' laser (stickered at '300mw') was a fair amount brighter than the other two, which were pretty equal compared to each other. So, still no clue what they actually shine at but at least there is a pecking order!
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Old 04-18-2010, 02:03 AM #13
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Default Re: Assessing some unknown lasers

Quote:
Originally Posted by joebob2000 View Post
I didn't take apart the crystal assembly (one was loose so I turned it til it made a nice point and then glued it in place.) By reassembly I mean the aluminium shell that goes around the laser assembly, and the entire enclosure. I think the fittings just dont conduct well. I noticed on some of the handheld projects on this site a set screw is used, is this the only way to get a good electrical connection?
Quote:
Originally Posted by joebob2000 View Post
After a bunch of screwing around, making sure the fittings were all tight and the laser lens was securely glued in place, each of the three is almost indistinguishable to the naked eye in terms of the visible beam path and the dot. However, in a very un-scientific test in a 100% dark room to see how much of the room gets lit up, I did confirm that the 'bigger' laser (stickered at '300mw') was a fair amount brighter than the other two, which were pretty equal compared to each other. So, still no clue what they actually shine at but at least there is a pecking order!
Yeah. You do not have to "move" the crystal set. Just pushing stuff around and/or tightening things up can sometimes affect the output.

Peace,
dave
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