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General Working Voltage for Lasers?

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This post is pretty simple: do lasers have a general working voltage just based on their power output (mW) or some other statistic?

I ask because I have seen several lasers now that have different "working voltages" based on what site I'm looking at so I'd like to just be able to look at one statistic and know what voltage the laser needs to perform at its peak. As you may know their are MANY lasers that say they require 2 X 16340s or 2 X 18350s, but whenever I see this I think, "can I just use a single 18650 instead and get 3500mAh instead of the horrible 1200mAh that dual 16340s/18350s hold?" I know dual 16340s/18350s will give 8.4V (7.4V nominal) so this is why I ask if there is any way to tell a laser's working voltage based on mW or some other statistic. Thanks!
 





DTR

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Laser diodes are current source not voltage source so they have a working current not a working voltage. They require constant current control and is the reason a laser driver is needed. If you are looking at modules that are a full units with a laser driver installed that can have a working voltage range. The diode driver combination will determine if you can use a single Li-ion or if two in series is needed. Also keep in mind a lot of units that require two cells use a bucking driver which will draw much less current than they give to the diode. For most blue and green diodes or even blueray diodes if they are in a configuration where you can use a singe cell it is most likely using a boost driver which can draw significantly more current than it is giving to the diode the extra current being used to boost the voltage. In the end with a lot of these scenarios even though you may have 1/3 the capacity in the two cell configuration you might be drawing 3X as much to go to a single cell with a boost and in the end you will still have a similar about of running time before the cell(s) need to be recharged. Boost drivers can in some configurations generate a lot more heat which may cause more work to set up or may have such high current demands requiing higher quality parts in the host to handle the current both making them a less attractive option in some cases. It all depends on the specific diode you are looking at then you can get an idea of your options.
 

diachi

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This post is pretty simple: do lasers have a general working voltage just based on their power output (mW) or some other statistic?

I ask because I have seen several lasers now that have different "working voltages" based on what site I'm looking at so I'd like to just be able to look at one statistic and know what voltage the laser needs to perform at its peak. As you may know their are MANY lasers that say they require 2 X 16340s or 2 X 18350s, but whenever I see this I think, "can I just use a single 18650 instead and get 3500mAh instead of the horrible 1200mAh that dual 16340s/18350s hold?" I know dual 16340s/18350s will give 8.4V (7.4V nominal) so this is why I ask if there is any way to tell a laser's working voltage based on mW or some other statistic. Thanks!


You can't tell what voltage the laser needs just by output power. It depends on the diode/driver combination in the case of diode or DPSS lasers. You could drive a diode that needs 7V with a single 18650 using a boost driver. Or you could drive a 7V diode with 8.4V using a low dropout buck driver. Just depends.
 
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Diachi, So once you find out what diode the laser is using how do you determine whether you'll need 1 battery cell or 2 battery cells? Or do I have to find out what driver its using to determine that?
 
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In response to your post DTR, I didn't know that a laser diodes that require 7V could use a single 18650...that was just me not knowing how batteries work. So do all lasers either have either a buck or a boost driver?
 
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diachi

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Diachi, So once you find out what diode the laser is using how do you determine whether you'll need 1 battery cell or 2 battery cells? Or do I have to find out what driver its using to determine that?

In response to your post DTR, I didn't know that a laser diodes that require 7V could use a single 18650...that was just me not knowing how batteries work. So do all lasers either have either a buck or a boost driver?


Yes, you need to know what driver it's using too.


And yes ... mostly, although some drivers are buck AND boost (Although, not both at the same time ... that wouldn't be possible). Don't know that I've seen any of those recently mind you.

My last green build had a PL515 diode, which runs at around 7V. It was driven by two regular 1.5V AAs, for 3V total, so less than a single 18650. There's limits to how far you can go of course. If it's outputing 7V at 100mA, it must consume at least 200mA at 3.5V (Actually more, nothing is 100% efficient) as power is always equal. Power out can never be greater than power in.
 
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I just read alot about Buck, boost, and buck boost drivers so I have a much better understanding of them now. If a laser had a boost driver and you used 2 3.7V cells could there be damage to the laser from over voltage?
 
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94Z28

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I just read alot about Buck, boost, and buck boost drivers so I have a much better understanding of them now. If a laser had a boost driver and you used 2 3.7V cells could there be damage to the laser from over voltage?

You can certainly kill a driver and diode by using 8.4v(7.4 nominal) in a boost driver..

Good example of this is a Single or Dual AAA led flashlight; some of them boost voltage to increase LED output. If you put two 4.2v lithium ion (3.7v nom) 10440 in it, you will overcurrent the LED and/or pop the driver.

Bottom line: You must know what diode to determine driver requirements. You must know what driver to determine cell requirements. You must know required draw of driver and diode to ensure a quality battery meets requirements.
 
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in a boost or buck driver? I've seen lots of lasers, including the Spiker from SanWu, that used a boost driver but takes 2 batteries (8/4V)...
 
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diachi

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You can certainly kill a driver and diode by using 8.4v(7.4 nominal) in a boost driver..

Good example of this is a Single or Dual AAA led flashlight; some of them boost voltage to increase LED output. If you put two 4.2v lithium ion (3.7v nom) 10440 in it, you will overcurrent the LED and/or pop the driver.

Bottom line: You must know what diode to determine driver requirements. You must know what driver to determine cell requirements. You must know required draw of driver and diode to ensure a quality battery meets requirements.

LED drivers are a little different seeing as they are mostly all voltage regulators. Good laser drivers are all current regulators, so in theory a driver designed only to boost that's receiving a higher input voltage than what it's supposed to be outputting at it's set current should just not work ... Of course, a cheaper/minimal/smaller driver may get cooked and may take the diode with it, or it may just cook the diode. Basically, your bottom line is correct - you must know what driver/diode/cell combination to use.

in a boost or buck driver? I've seen lots of lasers, including the Spiker from SanWu, that used a boost driver but takes 2 batteries (8/4V)...


If the output voltage is lower than the input voltage it is by definition not a boost driver. That may be a mistake on their site.
 
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Ok so I'm guessing a laser like the PL-E Pro is also uses a Buck driver?

Also, one thing I'm not getting is why laser manufacturers recommend not using protected batteries and instead get unprotected high drain batteries....
why not use a protected battery and why does the battery need to be high drain if a 4W laser only draws about 3.5amps?
 
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Encap

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in a boost or buck driver? I've seen lots of lasers, including the Spiker from SanWu, that used a boost driver but takes 2 batteries (8/4V)...

Saying boost or buck driver is like saying table or house---there a hundrads of different designs and possible driver designs with differining input and output parameters and different implementaion protocalls based on many factors. There are way to many for anyone to recite on LPF. Use google --study the subject.

See for basics : Laser Diode Driver Basics

See here for more information: https://www.ichaus.de/upload/pdf/WP4en_DesignTestFastLaserDriver_08082012.pdf

See also Sam's : Sam's Laser FAQ - Diode Laser Power Supplies

Are you plannng to design and build your own driver for a specific laser diode and build your own complete hand held laser?
 
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The ple pro is the host type. Depends on the diode and driver you get it with. The 532nm takes 1 cell. The 465nm takes 2 cells. Its stated on the site.
 
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dden4012, I would be getting the 3.5W 465nm version and I know it takes 2 cells but I was asking if its a buck or boost

Encap, I know there are hundreds of diffident individual drivers, but that's not my question. I was asking about the different TYPES of drivers and that would be Buck, Boost and Buck/Boost so I'm good now.
Thank you for all the links, and no I'm not planing on making my own setup. However, I still want to learn about the main components of a laser so I know what everything in a lasers description means and how it correlates to the batteries and the laser's performance

Bottom line: I'm satisfied with my understanding of drivers now, but still would like to know why manufacturers recommend unprotected high drain batteries
 
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