Ways to know how powerful a laser really is.
Will, Mon Sept 07 2009, 01:21PMFirst, it should be stated that I know there is such a thing as a laser power meter, but it is out of my price range at this time.
I purchased one of these “450mW†laser modules on eBay: Here.
I liked the layout of it and its heat-sink-ability and obviously the stated power output would’ve been awesome.
Now, in the past I’ve bought a 200mW laser pointer, which cost me 1/3 as much. Upon testing both units side-by-side I find that my laser pointer is as bright, or even BRIGHTER then this new module. With focusing, I also find that the 200mW burns things more readily as well. The seller was quick to say that the difference in wavelength would make a difference in burning things, but given that the pointer is 650nm and this module is stated to be 658nm I find such a claim preposterous.
So obviously this is very suspicious. I can’t help but think that I’ve just bought a $140 DVD burner diode in a slick package.
It should also be noted that this module has an acrylic lens, the laser pointer has a true glass lens. Now I’m no laser expert, but can an acrylic lens even *handle* 450mW??
The other questions thusly are:
What methods could be used to test the relitive power output of the laser?
Have you, or anyone you know of, purchased one of these and found it to be bogus?
Do you know of any similar modules avalible(looking for shear brightness here ['laser show' project] not so much burning things and such like that)?
Any help would be much appreciated.
-Will
Re: Ways to know how powerful a laser really is.
Steve Conner, Mon Sept 07 2009, 02:43PM
If you have a small solar cell, you could hook it up to a current meter, shine the lasers on it one at a time and compare the currents generated.
Looks like a DVD burner diode stuffed inside the case of a Dale wirewound resistor.
Steve Conner, Mon Sept 07 2009, 02:43PM
If you have a small solar cell, you could hook it up to a current meter, shine the lasers on it one at a time and compare the currents generated.
Looks like a DVD burner diode stuffed inside the case of a Dale wirewound resistor.
Re: Ways to know how powerful a laser really is.
Proud Mary, Mon Sept 07 2009, 02:49PM
Google: "bolometer"
Proud Mary, Mon Sept 07 2009, 02:49PM
Google: "bolometer"
Re: Ways to know how powerful a laser really is.
..., Mon Sept 07 2009, 06:10PM
Those modules are definitely a diode that was destined for a dvd-r drive (and there is about a 50% chance that it was salvaged from a drive) that has been stuffed inside a resistor case, and a cheep lens added.
As to measuring power, there are a few techniques that are available. The most accurate would be to send it to someone that has a real power meter for testing (I can do such things), but that involves mailing your laser.
The next best method would be to build this
which should give you a ballpark figure (is it 100mw or 400mw), but I wouldn't trust it to +/- 50% absolute or +/-10% relative (ie comparing your pointer to the module)
The final, least useful, method would be to use a silicon solar cell (or photodetector if no cells handy), and an attenuator (smoked plexiglass or other dark plastic would work well for this) to prevent from saturating the decector. Hook it up to an ammeter and see the current generated from each laser, you won't get an absolute value but you can get a relative value for the two lasers.
..., Mon Sept 07 2009, 06:10PM
Those modules are definitely a diode that was destined for a dvd-r drive (and there is about a 50% chance that it was salvaged from a drive) that has been stuffed inside a resistor case, and a cheep lens added.
As to measuring power, there are a few techniques that are available. The most accurate would be to send it to someone that has a real power meter for testing (I can do such things), but that involves mailing your laser.
The next best method would be to build this
which should give you a ballpark figure (is it 100mw or 400mw), but I wouldn't trust it to +/- 50% absolute or +/-10% relative (ie comparing your pointer to the module)The final, least useful, method would be to use a silicon solar cell (or photodetector if no cells handy), and an attenuator (smoked plexiglass or other dark plastic would work well for this) to prevent from saturating the decector. Hook it up to an ammeter and see the current generated from each laser, you won't get an absolute value but you can get a relative value for the two lasers.
Re: Ways to know how powerful a laser really is.
plazmatron, Mon Sept 07 2009, 06:47PM
There is no way I would consider using an acrylic lens in anything over 15mW.
8nm would make no noticeable difference, in a lasers ability to burn things.
I you haven`t got photocells or solar cells, you can always spray paint the bulb of a thermometer black. Record the temp, aim your (know output) laser pointer at it for say 30 sec, record the temp again. Allow the thermometer to cool back to ambient, and try the same with this diode module..
Les
plazmatron, Mon Sept 07 2009, 06:47PM
There is no way I would consider using an acrylic lens in anything over 15mW.
8nm would make no noticeable difference, in a lasers ability to burn things.
I you haven`t got photocells or solar cells, you can always spray paint the bulb of a thermometer black. Record the temp, aim your (know output) laser pointer at it for say 30 sec, record the temp again. Allow the thermometer to cool back to ambient, and try the same with this diode module..
Les
Re: Ways to know how powerful a laser really is.
lpfthings, Tue Sept 08 2009, 06:13AM
Wow, that description is unbelievably misleading! I am about 99% sure the diode used in that module was salvaged from some kind of DVD burner, but there is no way you could get 450mW from one for any amount of time. Even if it was 450mW, it'd still have a very, very hard time cutting wood!
I have built numerous laser modules with DVD diodes, and pushed them to the limits and none even came close to 450mW, maybe 300mW absolute max (Even with TEC cooling!) For that price I would recommend you try and get your money back, you can build a laser like that for less than $40 in parts!
For brightness, 635nm diodes would be the best, as the human eye is much more sensitive to it, than 650-660nm (This module). 635nm is pretty good for lasershow use, I've used it, and you can get 1-2W cmount 635nm diodes pretty cheap these days!
lpfthings, Tue Sept 08 2009, 06:13AM
Wow, that description is unbelievably misleading! I am about 99% sure the diode used in that module was salvaged from some kind of DVD burner, but there is no way you could get 450mW from one for any amount of time. Even if it was 450mW, it'd still have a very, very hard time cutting wood!
I have built numerous laser modules with DVD diodes, and pushed them to the limits and none even came close to 450mW, maybe 300mW absolute max (Even with TEC cooling!) For that price I would recommend you try and get your money back, you can build a laser like that for less than $40 in parts!
For brightness, 635nm diodes would be the best, as the human eye is much more sensitive to it, than 650-660nm (This module). 635nm is pretty good for lasershow use, I've used it, and you can get 1-2W cmount 635nm diodes pretty cheap these days!
Re: Ways to know how powerful a laser really is.
Will, Tue Sept 08 2009, 12:29PM
Hey thanks a lot for the help guys. I'll keep all these methodologies in mind in the future of my laser endeavors. The seller of this item has offered a full refund, possibly a good indication that this product isn’t near the advertised output. I’ll be sending it back, and looking into some 635nm diodes instead.
Thanks again.
Will, Tue Sept 08 2009, 12:29PM
Hey thanks a lot for the help guys. I'll keep all these methodologies in mind in the future of my laser endeavors. The seller of this item has offered a full refund, possibly a good indication that this product isn’t near the advertised output. I’ll be sending it back, and looking into some 635nm diodes instead.
Thanks again.
Re: Ways to know how powerful a laser really is.
Will, Thu Sept 10 2009, 03:58PM
Update: I had this module tested at a metrology lab through my connections at Cubic and the results came back unsurprising. This module puts out 150mW maximum, 650nm.
Don't buy these, don't even think about it.
I haven't seen such blatant fraud since I was sold an 'adiaas' jacket in San Francisco. At least those scammers never told me that it was authentic.
Will, Thu Sept 10 2009, 03:58PM
Update: I had this module tested at a metrology lab through my connections at Cubic and the results came back unsurprising. This module puts out 150mW maximum, 650nm.
Don't buy these, don't even think about it.
I haven't seen such blatant fraud since I was sold an 'adiaas' jacket in San Francisco. At least those scammers never told me that it was authentic.
Re: Ways to know how powerful a laser really is.
c4r0, Mon Sept 21 2009, 05:38PM
This is a laser module I made some time ago. It's a diode from 20x DVD-RW @ 600mA with acrylic lens collimator. As you can see it's 230mW.
c4r0, Mon Sept 21 2009, 05:38PM
This is a laser module I made some time ago. It's a diode from 20x DVD-RW @ 600mA with acrylic lens collimator. As you can see it's 230mW.
Re: Ways to know how powerful a laser really is.
EEYORE, Mon Oct 12 2009, 04:17PM
I really do hope that you leave a negative (not a neutral) feedback for the seller. This has become a new trend on ebay with lasers. People just claim whatever they feel like claiming. Its very annoying. Do not let them continue screwing people over with their junk lasers stuffed into a resistor heatsink.
Matt
EEYORE, Mon Oct 12 2009, 04:17PM
I really do hope that you leave a negative (not a neutral) feedback for the seller. This has become a new trend on ebay with lasers. People just claim whatever they feel like claiming. Its very annoying. Do not let them continue screwing people over with their junk lasers stuffed into a resistor heatsink.
Matt
Re: Ways to know how powerful a laser really is.
Meatball, Mon Oct 12 2009, 06:07PM
Ebay thugs like to use ignorance as a tool for sales. They think they can throw a diode in a module and get away with calling it a laser.
635nm 5.6mm diodes come in a 250mw at maximum. Most can be pushed further, but not for long.
If you must ebay your lasers, only buy from large companies.
Meatball, Mon Oct 12 2009, 06:07PM
Ebay thugs like to use ignorance as a tool for sales. They think they can throw a diode in a module and get away with calling it a laser.
635nm 5.6mm diodes come in a 250mw at maximum. Most can be pushed further, but not for long.
If you must ebay your lasers, only buy from large companies.
Re: Ways to know how powerful a laser really is.
LutzH, Sat Oct 17 2009, 08:16AM
Three Words: "Leave Appropriate Feedback" Most laser sellers on ebay are good, but nasty feedback helps throw out the bad apples. With China you have to watch it though, HK sellers are great, but mainland China sucks, they close after bad feeedback, and then re-open under a new name.
LutzH, Sat Oct 17 2009, 08:16AM
Three Words: "Leave Appropriate Feedback" Most laser sellers on ebay are good, but nasty feedback helps throw out the bad apples. With China you have to watch it though, HK sellers are great, but mainland China sucks, they close after bad feeedback, and then re-open under a new name.
Re: Ways to know how powerful a laser really is.
Will, Sun Oct 18 2009, 05:16AM
Here’s the thing about leaving this seller negative feedback: he refunded me, and didn’t even require me to return it the item. He was never rude and offered a full refund upon first asking if it was indeed the advertised output value. He did profess the stated output to be accurate, and that they test the laser's output with a meter prior to shipping, so that was a rather nasty lie.
Believe me I do wish to leave the appropriate feedback so that others don’t get caught in this fraud. In my case the seller made good, in every way within his power, on my purchase, therefore I don‘t feel a negative feedback would be justified.
Will, Sun Oct 18 2009, 05:16AM
Here’s the thing about leaving this seller negative feedback: he refunded me, and didn’t even require me to return it the item. He was never rude and offered a full refund upon first asking if it was indeed the advertised output value. He did profess the stated output to be accurate, and that they test the laser's output with a meter prior to shipping, so that was a rather nasty lie.
Believe me I do wish to leave the appropriate feedback so that others don’t get caught in this fraud. In my case the seller made good, in every way within his power, on my purchase, therefore I don‘t feel a negative feedback would be justified.
Re: Ways to know how powerful a laser really is.
Bored Chemist, Wed Oct 21 2009, 05:04PM
Long ago before ultrasound scans and such there was a doctor who ripped people off.
He offered a service to pregnant women where he would predict the sex of the child.
He asked for a urine sample then went to his "lab" to do the "test". In fact, once out of sight he just tossed a coin. Heads for a boy tails for a girl.
He charged a small fee for this service and, being fair minded, he gave back the money if he got the answer wrong.
Half the time he made a profit (by luck) half the time he didn't- but he made no loss.
Was his behaviour acceptable? If you found out about him would you have reported him?
Is it acceptable to provide a duff service and only pay back the money to the ones who complain?
I understand that it feels "wrong" to leave negative feedback in this case but how else do you stop the seller committing fraud?
Bored Chemist, Wed Oct 21 2009, 05:04PM
Long ago before ultrasound scans and such there was a doctor who ripped people off.
He offered a service to pregnant women where he would predict the sex of the child.
He asked for a urine sample then went to his "lab" to do the "test". In fact, once out of sight he just tossed a coin. Heads for a boy tails for a girl.
He charged a small fee for this service and, being fair minded, he gave back the money if he got the answer wrong.
Half the time he made a profit (by luck) half the time he didn't- but he made no loss.
Was his behaviour acceptable? If you found out about him would you have reported him?
Is it acceptable to provide a duff service and only pay back the money to the ones who complain?
I understand that it feels "wrong" to leave negative feedback in this case but how else do you stop the seller committing fraud?
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