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imyxh

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Hi, I'm Ian, I decided to make an account here after reading for a few days.
I got into laser pointers after getting 532 nm and and 405 nm Ebay lasers, both of which are now dead (surprise).

Um, what do I say about myself? I'm fluent in English and Mandarin, and I like making stuff. I lived for the first half of my life in Singapore and Malaysia.

I'm considering buying either a SanWu 304 or assembling a BDR-209 405 nm with a Survival host—though I hear that a class four laser like that is too dangerous for a beginner build.... I really want a 405 nm that I can use for astronomy and/or messing around with fluorescent materials with :). I know it's barely visible, I just love the color. Maybe an RB:M laser would be safer. :thinking:

I was wondering how voltage plays into the power of the laser ... because of W = V · A at a constant current more voltage should increase the power, right? So could I install a, say, ~500 mA driver and just use a weak battery to keep that BDR-209 at fairly low power? I would expect a guide on driver voltage and current to be stickied, but I couldn't find one in the search.


Oh, and what OD of eyewear do I need for either laser? The online tool by Laser Institute of America says OD 3 for 1 W and OD 2 for 100 mW 405 nm lasers ... is that accurate?

Thanks!
 
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paul1598419

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I don't think you realize how dim a 405nm laser looks. My 700 mW one is barely visible, but will burn your skin instantly. It will do worse to your retinas. You should think of getting a green laser as it is at the peak of human visual acuity. A 150 mW green would be more visible than a 1 watt 405nm one. Your choices in green are 505nm, 510nm, 515nm, 520nm and 532nm.
 
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imyxh

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paul1598419:
Yeah, I know they're really dim. I don't need the beam visible by day though, just being able to barely make it out at night would be great.
I might just get a 532 or 650 nm pointer for show and build a 405 nm as well.
I could also probably hack together a violet laser with a red and blue laser and some dichroic mirrors....​
 

Gazen

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paul1598419:
Yeah, I know they're really dim. I don't need the beam visible by day though, just being able to barely make it out at night would be great.
I might just get a 532 or 650 nm pointer for show and build a 405 nm as well.
I could also probably hack together a violet laser with a red and blue laser and some dichroic mirrors....​
How well one perceives 405nm light depends on the person. Personally my 200mW 405nm has a visible beam at night and inside, and the dot is very bright. Outside during day, the dot is hard to see past a couple meters.

You can buy one online for under $10, much cheaper than combining beams would be unless you already have the equipment.
 

Gazen

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Hi, I'm Ian, I decided to make an account here after reading for a few days.
I got into laser pointers after getting 532 nm and and 405 nm Ebay lasers, both of which are now dead (surprise).

Um, what do I say about myself? I'm fluent in English and Mandarin, and I like making stuff. I lived for the first half of my life in Singapore and Malaysia.

I'm considering buying either a SanWu 304 or assembling a BDR-209 405 nm with a Survival host—though I hear that a class four laser like that is too dangerous for a beginner build.... I really want a 405 nm that I can use for astronomy and/or messing around with fluorescent materials with :). I know it's barely visible, I just love the color. Maybe an RB:M laser would be safer. :thinking:

I was wondering how voltage plays into the power of the laser ... because of W = V · A at a constant current more voltage should increase the power, right? So could I install a, say, ~500 mA driver and just use a weak battery to keep that BDR-209 at fairly low power? I would expect a guide on driver voltage and current to be stickied, but I couldn't find one in the search.


Oh, and what OD of eyewear do I need for either laser? The online tool by Laser Institute of America says OD 3 for 1 W and OD 2 for 100 mW 405 nm lasers ... is that accurate?

Thanks!
Welcome Ian!

Sanwu is a reputable company, they make quality products. It’s generally advisable to start off with a lower power laser to learn with, but a class 4 laser is safe as long as you have the proper protection and understand its dangers.

As for OD, read this:
Laser Standards - NoIR LaserShields


It’s the logarithmic reciprocal of transmission. For example, and OD 1 pair of glasses will allow 10% of light of the rated wavelength to pass through, OD 2 1% and so on. For the ratings you provided the glasses would allow 1 mW of the laser to pass through, which should be safe.

If you power a diode with a power supply other than the one rated, it may change the wavelength of the output.
 
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imyxh

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If you power a diode with a power supply other than the one rated, it may change the wavelength of the output.
Whoa, that's odd. But how would I correctly match the voltage with batteries? With lithium batteries I can really only choose between 3.7 and 7.4 volts. Do I just look at DTR's photos of different currents being provided to the module with corresponding voltage, and select a driver current that matches an available battery voltage? I was hoping I could just select a single driver current and add more batteries when I wanted a more powerful laser ... how dramatic is the wavelength change?

Edit: oh, the photos DTR provided were of him changing the power anyway, not changing mA and V to keep a constant power. I was confused. But it shows him using 3.7 V for only 6 mW, and he stops before 7.4 V. I have no idea what battery voltage and driver current to use in a hand-held build now....
Say I want around 300 mW out of that laser. Would I just take 0.3 W / 3.7 V = 80 mW? That doesn't sound right. Maybe the voltage out of the driver is not the same as battery voltage.


Sorry for troubling everyone with a barrage of newb questions. :)
 
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paul1598419

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Direct diode lasers need a constant current driver to set the current. The voltage will change with temperature and so it is necessary to keep the current constant no matter what the voltage drop across the diode is at any time while it is on. The batteries have little to do with it as long as they can supply enough power to drive the diode. If you power the diode with something besides a CC driver it will either blow the diode up or not power it on. A change in wavelength depends on the type of diode used. There aren't many that will increase their wavelength considerably with increased current.
 
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imyxh

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Ah, so battery voltage doesn't need to be specific? That's easier. I was confused by the voltage/current/power photos on DTR's page for the diode. I assumed that was his input voltage to the left of the output current from the driver, but I think it's something else.

So to clear things up, the driver current I set will change the brightness of the diode, but the battery voltage won't?
When descriptions for hosts like this one say things like "Uses two rechargeable RCR123A or disposable CR123A batteries or an 18650 battery depending on the diode used," how do I know what type I should use? I know that two RCR123A in series should be twice the voltage of the 18650, but not which one I'd choose for different diodes.

Thanks for everyone's help!

Edit: just noticed:
You can buy one online for under $10
Really? I was wary about buying a laser from someplace other than Sanwu or DTR. Can you recommend a 200 mw 405 nm cheaper than Sanwu's pocket laser? I couldn't find much in the reputable sellers thread.
 
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Encap

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Welcome Ian. Enjoy the forum. It is one of the great ones as forums go.
Wow Fluent in English and Mandarin---that should come in handy as well as make you a very valuable business resource/employee in today's business world.
I would guess you also speak Singlish/colloquial Singaporean English having lived in Singapore---no?
 
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imyxh

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Encap:
I've noticed that forums aren't usually anywhere near as toxic as the rest of social media. Hope this one lasts.

I can understand Singlish and Malaysian English.
I misspoke (mistyped?), though. Chinese is my first language and I'm a native speaker, but not quite fluent in it yet. My English is much better.
 

imyxh

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Found the answer to my battery question on another thread:

The diode pulls the voltage it needs from the battery via the driver modulation.
Most drivers aren't engineered for such a variation , thus it is CRUCIAL to ask the manufacturer about the specs before doing so.

For example , while Survival Laser's driver can cope with both 2 RC123A cells or 1 18650 cell.
CNI's lasers are specifically engineered for ONE 18650 cell.
Indeed, the page for the driver says "recommended input voltage of 4.2 to 8.4 volts."
So two RC123A cells, then.
 
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GSS

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Welcome Ian!

Sanwu is a reputable company, they make quality products. It’s generally advisable to start off with a lower power laser to learn with, but a class 4 laser is safe as long as you have the proper protection and understand its dangers.

As for OD, read this:
Laser Standards - NoIR LaserShields


It’s the logarithmic reciprocal of transmission. For example, and OD 1 pair of glasses will allow 10% of light of the rated wavelength to pass through, OD 2 1% and so on. For the ratings you provided the glasses would allow 1 mW of the laser to pass through, which should be safe.

If you power a diode with a power supply other than the one rated, it may change the wavelength of the output.
Gazen, I wouldn't think the OP is ready to push a diode for a few nm of WL changes at this time??
My 700mw 405nm is not what you would call visible at night..

Imyxh, welcome:) Paul mentioned and gave you a few greens WL's that would best fit your astronomy needs..A higher WL blue might satistfy your color liking..
 
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imyxh

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My 700mw 405nm is not what you would call visible at night..
Hmm, really. I had a "<5 mW" (actually said <100 mW on the label) 405 nm that was visible if you looked down the beam—looking at the dot, of course.

There are a few nice green diodes around, though, like this one.
 

GSS

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Hmm, really. I had a "<5 mW" (actually said <100 mW on the label) 405 nm that was visible if you looked down the beam—looking at the dot, of course.

There are a few nice green diodes around, though, like this one.
It was most likely more than 5mw if it was an ebay 405, probably 60 to 80mw..but it won't be a good astronomy pointer..
That Dtr. PL 520 you just linked is yes a very good diode for your needs.
It will stable when its cold out and has very good beam spec's:)
 
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paul1598419

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Hmm, really. I had a "<5 mW" (actually said <100 mW on the label) 405 nm that was visible if you looked down the beam—looking at the dot, of course.

There are a few nice green diodes around, though, like this one.
That would be a good choice, but you will need it pressed into a module and have a driver for it. The bare diode is $25.00, but the pressed and driven one is $65.00 with an acrylic lens. You will still need a single Li-ion battery to power it as it is a boost driver and a host with a heat sink to put it into. You must always consider what else you will need to complete a build as a bare laser diode is only one factor.
 

imyxh

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Yeah I was looking at host kits with drivers installed. Is there any reason I should use the DTR assembled drivers as opposed to just getting the module with leads and using the driver from my kit, set to an appropriate current?

Still not sure how much I care about astronomy and beam visibility to build something other than a 405, though that emerald diode would look pretty too....
I'll end up spending lots of money on this, won't I. :)
 




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