# Ebay Laser Purchase by Newbie



## SeamusORiley (Jan 5, 2013)

I purchased a laser from ebay for under $30 in which it claimed to be able to light a match (from photo)...not so. 
Is this a regular claim among sellers from China/Hong Kong, but aren't strong enough to pop a balloon or light a match?

It is still a fascinating pointer laser and my daughter and I will use it for her science experiment (through water, through ice, through smoke, etc) but I am wondering about why it is sold with a "child safety lock" (key) when it is not strong enough to light a match, for example. I have read up on the general safety issues (goggles, no eyes, no planes, etc). 

Is there a limit to what strength can be sold via ebay?

thanks...


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## eebowler (Jan 5, 2013)

"I am wondering about why it is sold with a "child safety lock" (key) when it is not strong enough to light a match, for example" Because it can't light a match doesn't mean it wouldn't kill the cells in your retina.


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## PhotonWrangler (Jan 5, 2013)

Chances are that some lasers in that batch can light matches and others can't. I've seen quite a bit of variation in laser pointers, especially green ones. The MCA in green lasers is sensitive to vibration and can shift.


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## mhemling33 (Jan 6, 2013)

please read this it might help answer all your questions.

http://laserpointerforums.com/f45/guide-buying-your-first-green-laser-30608.html


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## VegasF6 (Jan 8, 2013)

*Hazardous materials policy – laser pointers*
From 1st November we'll be extending our Hazardous Materials policy to include laser pointers. 
Listings of hand-held lasers with an output of more than 1mW are generally not permitted on eBay. The only exceptions to this policy are club/disco/'rave' type lasers, which may generally be listed, even if their output is greater than 1mW. For further information on laser safety, please visit the HPA website. 
http://www2.ebay.com/aw/uk/200810210948412.html

Despite this fact I know of people who have bought small AAA laser pointers that I tested on LPM of over 50mW for 45 second test. I expected the output to drop in that time frame, but surprisingly they seemed pretty steady.


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## SeamusORiley (Jan 13, 2013)

no it is 18650 battery. 

I didn't respond to the child lock and retina reply. I was asking about the power, not about allowing a child to play with it. Retina damage can come from the 3.99 lasers sold at the checkout counter at Walmart. I was specifically asking about the child-lock added to the laser pointer from ebay. 

I am curious as to the power, but even up close, and fine focused to its smallest point, it did not light a match, as advertised. The reflective glow, off the match, is very strong, and even though I wear glasses, it is uncomfortably bright. I am doing some online research to help my daughter in her science fair; laser light through water, ice, etc. I was only seeking information from those experienced in lasers.


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## PhotonWrangler (Jan 13, 2013)

SeamusORiley said:


> no it is 18650 battery.
> 
> I didn't respond to the child lock and retina reply. I was asking about the power, not about allowing a child to play with it. Retina damage can come from the 3.99 lasers sold at the checkout counter at Walmart. I was specifically asking about the child-lock added to the laser pointer from ebay.
> 
> I am curious as to the power, but even up close, and fine focused to its smallest point, it did not light a match, as advertised. The reflective glow, off the match, is very strong, and even though I wear glasses, it is uncomfortably bright. I am doing some online research to help my daughter in her science fair; laser light through water, ice, etc. I was only seeking information from those experienced in lasers.



If you have access to the school's science lab through your daughter, ask if they have a laser power meter. This will eliminate the guesswork. I believe you need to be in the >50mw range to be able to ignite things.

Be safe.


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## VegasF6 (Jan 13, 2013)

SeamusORiley said:


> I purchased a laser from ebay for under $30 in which it claimed to be able to light a match (from photo)...not so.
> Is this a regular claim among sellers from China/Hong Kong, but aren't strong enough to pop a balloon or light a match?
> 
> It is still a fascinating pointer laser and my daughter and I will use it for her science experiment (through water, through ice, through smoke, etc) but I am wondering about why it is sold with a "child safety lock" (key) when it is not strong enough to light a match, for example. I have read up on the general safety issues (goggles, no eyes, no planes, etc).
> ...


A: Yes, it is a common claim for unethical sellers regardless of country. They claim so because it has become a common benchmark for the newly initiated and I imagine it's a question many sellers are asked.

B: It is sold with a safety lock, most probably, because in some countries, for instance in the US, the govering body (USFDA) require a key switch to be installed on class IIIB and higher laser. By including this key lock on this lower power laser, they infer that perhaps THEIR laser is actually high power, without actually saying so. They let the buyer "draw their own conclusions."
http://www.fda.gov/Radiation-Emitti...ent/LaserProductsandInstruments/ucm116373.htm

C: Yes, there is a limit, it is 1mW as I posted above, in MOST circumstances.

*edit* I just realized the hazardous materials policy I listed which states 1mW is for the UK.


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## n2stuff (Jan 13, 2013)

OP. Do you have the link to the laser? Also Feebay will let you sell a 5mW or less laser. To sell a laser greater than 5mW in the US it needs more than key lock such as a beam stop, delay start, key lock ect. And as you found out people lie about output of lasers and flashlights. If you are going to try and burn stuff please get some safety glasses for you and your kido.


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## SeamusORiley (Jan 25, 2013)

We have been working with various ideas for her science fair; laser through ice, water, and now through a prism. Interestingly enough, I put it through a small magnifying glass to a match, which was colored black by a marker, and it lit. She is looking for demo ideas, just basic stuff. Besides water, ice, magnifying glass and prism, any other ideas?


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## VegasF6 (Jan 25, 2013)

Vaseline glass, uranium doped marbles, phosphorus layer on led and fluorescent bulb. Laser spirograph, = small motor, mirror and springs. Beam splitter. Those different caps that create shapes and designs, whatever the heck they are called 

*edit*
Here is what I meant, gratings. 
http://www.ebay.com/itm/5-Patterns-...406?pt=LH_DefaultDomain_0&hash=item3a7781056e

*edit edit*
Hmm, I just realized I don't think you ever said what color laser you have? I would guess green or red. The things I mentioned for flourescing would only be for UV laser. Sorry.


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## PhotonWrangler (Jan 25, 2013)

SeamusORiley said:


> We have been working with various ideas for her science fair; laser through ice, water, and now through a prism. Interestingly enough, I put it through a small magnifying glass to a match, which was colored black by a marker, and it lit. She is looking for demo ideas, just basic stuff. Besides water, ice, magnifying glass and prism, any other ideas?



Set up a bare loudspeaker connected to an audio source. Bounce the laser off the center of the speaker cone (place a small mirror there if it's not already silver colored) and pick up the reflections from the vibrating speaker with a solar cell connected to an amplifier across the room. You can demonstrate an externally modulated laser beam this way.

Along similar lines, check out this article on how to use a laser to visualize your voice.


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## VegasF6 (Jan 25, 2013)

I like PWs ideas, very cool.
Here is another visual representation of audio signal on you tube.


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## bshanahan14rulz (Jan 28, 2013)

http://en.wikipedia.org/wiki/Double-slit_experiment < probably not for the project, but interesting enough for you to try with or without your daughter.

You could have a setup with some sort of colloidal or homogenized mixture in water, just something so the beam is visible in the water. Then, you can show how you can move the focal point by changing the distance of the collimating lens. 

I would want to replace the tiny aspheric with a much larger one. You lose coupling efficiency, but gain a macro sized view of the beam.


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## PhotonWrangler (Jan 28, 2013)

1) Scan a laser beam in a straight line from left to right on a wall at a fairly slow speed, just barely fast enough to produce a solid line. 
2) While looking at the line on the wall, take a bite out of a carrot or an apple.
3) You will see the waveform of the audio crunching sound in the laser line. This is because your eyeballs jiggle when you crunch something in your mouth.


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