Old 01-08-2016, 05:51 PM #1
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Default cheap, so called 5mW Chinese green pointers

Hello to all, new to the forum. I had seen a thread similar to this, but the search feature won't work for me. Maybe it's my browser , I dunno. So I'm sorry for creating a new thread.

I have bought, so far, 2 cheap green pointers on eBay. I want a 5mW pointer! Which is why I purchased THESE. Upon powering either one up, which were from two different shops, they are obviously way beyond 5mW. Mmaybe 10's of milliwatts.

I know the dangers of lasers, I do have a cheapo pair of safety goggles effective for filtering green. The problem is ,they filter nearly ALL of it. These pointers are the new lm358 based drivers without an adjustable potentiometer. Does anyone know anything about these drivers and which resistor controls diode current? If I destroy it, I really don't care. It cost nothing and ,being a ham radio operator who builds his own equipment, I have plenty of parts to spare.

I thought about trying an lm317 based regulator because I have like 50 of them. I'm just not sure that is appropriate for this type of laser. I just thought I would ask the laser guys before I began tinkering myself.

Like I said, I want an eye safe 5mW and I already put an IR filter in that I removed from an old camera. High powered greenies are beautiful, but I'm just too clumsy; and I'm very nervous wielding that much power! Thanks to anyone who is kind enough to provide any suggestions.


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Old 01-08-2016, 05:58 PM #2
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Default Re: cheap, so called 5mW Chinese green pointers

That's the problem with those cheap greens from China unfortunately, my "5mW" pointer hits 93mW on the meter. Sounds like your glasses are working as intended though, so that's good - if you could see any more than a faint glow that wouldn't be a good sign.

As for a replacement driver, yes, you could drive one of these with an LM317 - however, it may take some trial and error - the crystals may not want to lase reliably at such a low power. The other problem is finding the right current, so as not to blow the diode. I'd start at maybe no more than 200-300mA and work my way down. You'll need to use an LM317 set up for constant current, which can be made adjustable with a pot. Look up the DDL circuit - should be some "schematics" on Google images, or you can use the white search bar at the bottom of the page here to search the forum with Google.

It sounds like you're using the forums built in search (near the top of the page), which is for all intents and purposes, useless. Try the one at the bottom!

Also, 73's de VE8AEG

Edit: Also - I should add, sometimes these pointers are impossible to disassemble without completely destroying them. Just FYI
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Last edited by diachi; 01-08-2016 at 06:11 PM.
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Old 01-08-2016, 06:13 PM #3
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Originally Posted by diachi View Post
That's the problem with those cheap greens from China unfortunately, my "5mW" pointer hits 93mW on the meter. Sounds like your glasses are working as intended though, so that's good - if you could see any more than a faint glow that wouldn't be a good sign.

As for a replacement driver, yes, you could drive one of these with an LM317 - however, it may take some trial and error - the crystals may not want to lase reliably at such a low power. The other problem is finding the right current, so as not to blow the diode. I'd start at maybe no more than 200-300mA and work my way down. You'll need to use an LM317 set up for constant current, which can be made adjustable with a pot. Look up the DDL circuit - should be some "schematics" on Google images, or you can use the white search bar at the bottom of the page here to search the forum with Google.

It sounds like you're using the forums built in search (near the top of the page), which is for all intents and purposes, useless. Try the one at the bottom!

Also, 73's de VE8AEG
Thanks for the reply. Wow 93mW advertised as 5mW! ? That's insane! And very dangerous to unsuspecting consumers. Seems like these people have another agenda besides making money!

As for the lm317 route, I think I'll start there then. I just didn't know if these were pulsed at high frequency or continuously on. And yeah, the goggles, on eBay, filter virtually everything except a pin sized, dimly lit dot. I was weary of them since they were so cheap. Thanks again,

And 73 de kj4ovu
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Old 01-08-2016, 06:25 PM #4
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Default Re: cheap, so called 5mW Chinese green pointers

Quote:
Originally Posted by mojojojo View Post
Thanks for the reply. Wow 93mW advertised as 5mW! ? That's insane! And very dangerous to unsuspecting consumers. Seems like these people have another agenda besides making money!

As for the lm317 route, I think I'll start there then. I just didn't know if these were pulsed at high frequency or continuously on. And yeah, the goggles, on eBay, filter virtually everything except a pin sized, dimly lit dot. I was weary of them since they were so cheap. Thanks again,

And 73 de kj4ovu
I don't think they have an agenda, just no form of quality control to confirm power output - the power from the pens I have can vary wildly from pen to pen. But yes, you are correct, not good for customers that are expecting something safe!

Yes, the LM317 is constant output - although they can be modulated at a remarkably high frequency. There's a schematic out there for a laser driver built around an LM317 (OR the LM338 If memory serves me correctly!) that can be modulated up to 1MHz - In fact, I recall reading somewhere that a ham built an 80m transmitter around the LM317, so it's capable of more than 1MHz if that story is accurate.

Edit: http://www.qsl.net/qrp/tx/317-tx.htm - I was wrong, it was on 160m, still impressive! I'd build it if I knew CW and had my advanced ...

As for glasses, really it is best to spend the $50 or so dollars on a good set that are properly tested, but for the kind of powers you are using I think you'll be just fine - the only thing to worry about is stray IR, but you seem to have that covered.
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450nm | LaserPointerStore - Thor H2 | 1.6W Metered | Review Unit | >>Review<<
473nm | B&W Tek BWB-10-OEM |
488nm | Spectra Physics 163 Argon | ~30mW Metered |
495nm | Laser66 Pen Build | WIP
515nm | PL515 Pen Build | 50mW | >>Build Thread<<
520nm | Laserlands 520 5mW | 3mW Metered | Review Unit | >>Review<<
532nm | Gearbest 303 Pointer | 50mW Metered
532nm | Gearbest JD-850 Pointer | 30mW Metered |
633nm | HeNe | 6mW
633nm | Spectra Physics 155 HeNe | <1mW >>Thread<<
650nm | Sanwu Laser Pocket Series | 200mW Metered
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Last edited by diachi; 01-08-2016 at 06:30 PM.
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Old 01-08-2016, 07:11 PM #5
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Default Re: cheap, so called 5mW Chinese green pointers

Do you have the funds to buy from a good company such as "optotronics" their 5mw green is garrenteed to be 4.99mw or a fraction less with an IR filter. It will also last for years.
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Old 01-08-2016, 08:38 PM #6
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Do you have the funds to buy from a good company such as "optotronics" their 5mw green is garrenteed to be 4.99mw or a fraction less with an IR filter. It will also last for years.
Yeah, I've began to wonder where the legitimate retailers have gone. I just got laid off last week so I'm trying to be a bit careful. So if I have to pay a ridiculous amount for a safe pointer, I might just stick to the cheap ones at Wal-Mart :/

Of course if I could find one <$20-30 bucks I might consider. I've already been had that amount with the con artist who sell on eBay! I'll check out the site you recommended.
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