# Green Lasers- Question about watts,amps,volts



## Uisgdlyast (Aug 14, 2004)

This really doesnt have to be about green lasers only but i was wondering if someone could explain the differences between amps, watts, and volts and how they work in a laser(or any other device). Its been awhile since i took electronics and even then i barely understood the differences, they always used some analogy like a pipe and the water was electricity, the water pressure was volts, etc. 
I know that by increasing the current you will also increase the watts, right? But then how do you increase the watts just by diode alignment? 


Also how can i meausure the amps of my grean laser? i know i have a good DMM around somewhere but i dont knwo how to make it work for a laser and if i end up modding mine i dont want to blow it.

Thanks


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## TTaz (Aug 14, 2004)

[ QUOTE ]
*Uisgdlyast said:*
Also how can i meausure the amps of my grean laser? i know i have a good DMM around somewhere but i dont knwo how to make it work for a laser and if i end up modding mine i dont want to blow it.

[/ QUOTE ]

-If you talk about measuring the optical power output, I can't help you since you must have a receptor associated with the DMM... and the formula to convert µA/mA of the receptor into optical mW

-If you talk about measuring the current consumption of a device, you have to 'cut' the original circuit to insert the DMM.

for example, the cap of the batteries removed :
[-] side of the device ---> [A/mA/red] side of the DMM
[-] side of the set of batteries ---> [COM/black] side of the DMM

The DMM set to Amps, and keep in mind that the fact of inserting the DMM in the circuit will modify a little the current consuption of the device ('cause the DMM is seen like a resistor by the rest of the circuit)
I mean that the current the DMM will give you (for example 310 mA) will not be exactly the current without it (say...315 MA for example)

[ QUOTE ]
*Uisgdlyast said:*
if someone could explain the differences between amps, watts, and volts and how they work

[/ QUOTE ]

Volts are 'fixed' by the batteries (3V), Amps are determined by the device you power (say 300mA for a laser), Watts represent the power consumption of the device : 3V * 300mA == 900mW 
so, say 900mW at 3V for a laser (5mW / 900mW leads to a 0.5% efficiency)
but this consumption can vary with the voltage applied by the batteries, for example if the laser is seen by the batteries like a resistor, you can have :
- 1.024W @ 3.2V
- 625mW @ 2.5 V


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## Uisgdlyast (Aug 14, 2004)

[ QUOTE ]
*TTaz said:*


-If you talk about measuring the current consumption of a device, you have to 'cut' the original circuit to insert the DMM.

for example, the cap of the batteries removed :
[-] side of the device ---> [A/mA/red] side of the DMM
[-] side of the set of batteries ---> [COM/black] side of the DMM

The DMM set to Amps, and keep in mind that the fact of inserting the DMM in the circuit will modify a little the current consuption of the device ('cause the DMM is seen like a resistor by the rest of the circuit)
I mean that the current the DMM will give you (for example 310 mA) will not be exactly the current without it (say...315 MA for example)

[/ QUOTE ]

Ok, I know I need to "cut" the circuit but I'm not exactly sure where to put the ends to measure and if i have to open it up, which i dont want to open it just yet. And if i do open it how would i go about connecting a power supply(my batteries) to it?


[ QUOTE ]
*TTaz said:*
Volts are 'fixed' by the batteries (3V), Amps are determined by the device you power (say 300mA for a laser), Watts represent the power consumption of the device : 3V * 300mA == 900mW 
so, say 900mW at 3V for a laser (5mW / 900mW leads to a 0.5% efficiency)
but this consumption can vary with the voltage applied by the batteries, for example if the laser is seen by the batteries like a resistor, you can have :
- 1.024W @ 3.2V
- 625mW @ 2.5 V 

[/ QUOTE ]

Thanks, I really just needed to know that watts are the consumption. If anyone wants to add more info to this feel free. Actually add as much as you like, I understand the basics of how they work. I'll try to read about it on my own though. Mostly how they relate together, I'm a little confused on how you can have a 3v source but change the amount of current(I'm actually good with this stuff too, i shoudl of paid more attention to the theory in electronics class)

thanks


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## TTaz (Aug 14, 2004)

you don't have to open the device, just remove the cap for the batteries (don't -yet- have a pointer, but I imagine that the case makes the [-] path for current)

[ QUOTE ]
*Uisgdlyast said:*
I'm a little confused on how you can have a 3v source but change the amount of current

[/ QUOTE ]

take this smiley : /ubbthreads/images/graemlins/smoker5.gif there is a level difference between the reservoir and the ground (this is the 3V), you can adjust different diameters of tubing, there always will be the same 'potential difference' (the same hight), but the 'current' will be more important if the tubing is larger /ubbthreads/images/graemlins/wink.gif


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## Uisgdlyast (Aug 14, 2004)

ok, great. I actually love electronics but i'm a little behind on the theory.

Actually the casing provides the positive current? does it not?

Anyways i think i understand better how to do it now and i'm going to go try once i find my DMM in the mess i have


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## TTaz (Aug 14, 2004)

[ QUOTE ]
*Uisgdlyast said:*
Actually the casing provides the positive current? does it not?

[/ QUOTE ]

In fact, I don't know how the batteries are to be placed.... [-] or [+] side at bottom...

Anyway... I'm in electronics since I have 8 years old (and I'm 25 now), so feel free to ask if you have any question on this vast subject /ubbthreads/images/graemlins/wink2.gif


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## The_LED_Museum (Aug 14, 2004)

If you wish to find the power output of your green laser, connect a single solar cell (the matte black type) to the meter, set it on low amps (the 1 amp or 2 amp scale), shine the laser at the solar cell, and use the following formula:

*(current in amps as shown on the meter)*1239.7/532/0.97*

If I remember correctly, the resulting value will be your laser pointer's power in watts. A final value of 0.04967 would equate to a laser power of just a tick under 50mW.

*IMPORTANT:* This mathematical formula will not work properly if you remove the IR filter from your green laser pointer. You will not get a correct measurement for the 532nm green laser line, and the formula is not correct for the 808nm and 1064nm laser lines that will be emitted by the laser with the IR filter removed either.


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## Uisgdlyast (Aug 15, 2004)

where can i get these solar cells?
I still would like to get a reading in mA but i cant figure out how to connect it together without opening it


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## Crosman451 (Aug 15, 2004)

Pictures worth a thousand.....


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## lasercrazy (Aug 15, 2004)

What kind of mw output are you getting off that 205 ma pointer?


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## Crosman451 (Aug 15, 2004)

On this particular pointer 23.3mW which is very good. This one cranked up in current would probably do somewhere in the 30mW to 40mW range from past experience.


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## The_LED_Museum (Aug 15, 2004)

[ QUOTE ]
*Uisgdlyast said:*
where can i get these solar cells?

[/ QUOTE ]
I'm really not sure where you would be able to get one of these solar cells. I broke mine a couple of years ago, and do not yet have a replacement for it. /ubbthreads/images/graemlins/jpshakehead.gif


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## Uisgdlyast (Aug 15, 2004)

[ QUOTE ]
*Crosman451 said:*
Pictures worth a thousand.....







[/ QUOTE ]

Thanks, i'm off to find my DMM now.

Also how much is a laser reading reading device like you have cost? it looks pretty small


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## Crosman451 (Aug 15, 2004)

Go to this link http://www.coherentinc.com/Products/index.cfm?fuseaction=Interfaces.Product&PCID=4&PLID=94&PDID=250

The Coherent LaserCheck power meter is one of the easiest to use meters out there. It is small like a oversized pen and can measure from 1mW to 1000mW. Ranges from 400nm to 1064nm. One of the most useful tools I've ever purchased.


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## The_LED_Museum (Aug 15, 2004)

You can also get them at Edmund Scientific.
http://www.edmundoptics.com/onlinecatalog/DisplayProduct.cfm?productid=1403
Expect to pay $310.00 for it.
I think you can measure 0.5µW (0.5 microwatts) to 1,000mW, at wavelengths of 400nm to 1,064nm.


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## Crosman451 (Aug 16, 2004)

Here is some of the equipment that I use for testing power and energy of lasers. Several detector heads are required for the different types of lasers and power outputs. The LM-1 head is very accurate for measuring up to 1000mW. The large round one is good for 100W! The Coherent Field Master GS has served me well for the last couple of years for various larger lasers. But for the money the small pen LaserCheck is so convienent it's hard to beat for the smaller lasers, especially pointers.


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## Uisgdlyast (Aug 17, 2004)

wow, crosman, i gotta ask what do you do for a living? or are lasers just a hobby?


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## Crosman451 (Aug 17, 2004)

At this point, just an "Expensive Hobby" /ubbthreads/images/graemlins/mecry.gif /ubbthreads/images/graemlins/mecry.gif /ubbthreads/images/graemlins/mecry.gif

It started with a lust for knowing just "what is the power output" of this laser. The LaserCheck is OK, but records a sampling of the lasers output. It checks for 2 seconds and locks in a reading. I wanted to read "real time", so the Field Master GS was the next logical step along with the different detector heads. This equipment was "necessary" for my mods. Ah, the thirst accurate knowledge, my weakness.
/ubbthreads/images/graemlins/help.gif /ubbthreads/images/graemlins/help.gif

/ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/banghead.gif


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## Uisgdlyast (Aug 17, 2004)

crap.. sounds like what would happen to me if i had more money.

Mind if i ask what kind of lasers(and how many) you own? I mean if you can measure 100W you gotta have something cool.

Also any tips on getting the greenies end cap off? must of spent an hour on it with a razor blade and all i got off was the paint /ubbthreads/images/graemlins/frown.gif


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## Crosman451 (Aug 17, 2004)

Several HeNe lasers of various powers, a few argons from 60 to over 200mW plus. Larger argons up to 3W and a white light system over 4W. Not to mention the green DPSS stuff, 20mW to 300mW. Red diodes of all sorts and a very unique violet 409nm pointer. All I'am admitting to, for now./ubbthreads/images/graemlins/sssh.gif

What kind of pointer do you have anyway? Leadlight or Changchun.


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## Uisgdlyast (Aug 17, 2004)

It's a leadlight, i was able to tweak the pot a little but can't get the front off.

That sounds like a nice collection, is there really any use for lasers besides the "theyre just cool" factor?

Also is your 300mW green DPSS a pointer or a module? I'd love to see one of those in action(actually i'd like to see those argons)


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## Crosman451 (Aug 17, 2004)

Uisgdlyast- Go to, 

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=548258&page=9&view=collapsed&sb=5&o=365&fpart=1

for some pics on the custom 300mW hand held.

Why do you want to take the front cap off of your Leadlight? If you have been able to tweak the pot, thats as far as I would go for a simple power increase.

I'll try to post more pic's on the thread asking about posting green laser pictures later tonight.


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## Uisgdlyast (Aug 17, 2004)

yeah but i heard that you can get a lot more with a diode adjustment and i would like to give that a shot


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## moshen (Aug 17, 2004)

LED Museum, try the green LED measure method. By using the photoelectric effect and a linear response..you can extrapolate the power...
http://www.greenlaserforum.rauch.co.uk/phpBB2/viewtopic.php?t=10

Let me know your results.


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## The_LED_Museum (Aug 17, 2004)

What kind of green LED do I need to use?
The older GaP / GaAlP yellow-green, or the newer InGaN emerald-green?


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## moshen (Aug 18, 2004)

I think the InGaN one is one people have been using. I got mine from radioshack. 5mm green LED.


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## The_LED_Museum (Aug 18, 2004)

I'll try with an InGaN green LED tomorrow, midmorning (around 9:00am PDT), and report back here with my findings.
Fair enough?


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## The_LED_Museum (Aug 18, 2004)

I tried an InGaN green LED, and got a reading peaking at 12µA with a green laser known to output 57.6mW.
The meter was set to the 200µA scale - the lowest it goes.


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## Uisgdlyast (Aug 18, 2004)

sounds like it should be higher than 12... i'd try the other LED.

Also... i still cant get the cap off /ubbthreads/images/graemlins/smile.gif


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## The_LED_Museum (Aug 18, 2004)

I don't have a GaP or GaAlP green LED - not handy anyway - so I cannot re-do the test with that LED on a moment's notice. When I find one, I'll re-do the test and post my results here.


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## The_LED_Museum (Aug 18, 2004)

*1,004µA* using a Kingbright yellow-green LED. I don't know if it's GaP or GaAlP, but it produces that characteristic "yucky" yellow-green of this type of LED when energised; as opposed to the pure whitish green output by a typical InGaN green LED.

Much, much, much higher than the reading I obtained with an InGaN green LED.


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## Uisgdlyast (Aug 18, 2004)

well according to the greenlaser forum thats way too high now... they said 14µA was for 5mW


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## The_LED_Museum (Aug 18, 2004)

I used a 50mW laser that measured 57.6mW.
Let's do the math here...BRB...should have gotten a reading of around 157-160µA. Ouch.
1,004µA *is* too high. Ouch.


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## Uisgdlyast (Aug 18, 2004)

what did you use to measure it at 57.4mW?
What we need is someone with a laser meter and some free time on their hands to come up with a sheap way to measure mW and make sure its accurate.

They would need a constant though, like using the same laser and just modifying the current and then testing other lasers to see if the method actually works


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## moshen (Aug 18, 2004)

I used a 5mm green LED from radioshack. Since it's readily available lets standardize ourselves with that. Besides I seem to be getting readings in range as to what I should be expecting!


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## moshen (Aug 18, 2004)

Crosmman451, if you can it'll be awesome if you got a 5mm green LED from radioshack and crosschecked the ratios for us. It should be a linear response..we just need a verification of the correct ratio for a standardized LED...


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## TTaz (Aug 18, 2004)

Another ways of building a Homemade Laser Power Meter :

http://repairfaq.ece.drexel.edu/sam/laserioi.htm#ioilpm3

EDIT :
------
I'll pick and try one or more of these and I'll try to evaluate and 'calibrate' these at the ESPEO (Ecole Supérieure Des Procédés Electroniques et Optiques == Hi-School of Electronic and Optical Processes)


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## The_LED_Museum (Aug 18, 2004)

[ QUOTE ]
*Uisgdlyast said:*
what did you use to measure it at 57.4mW? 

[/ QUOTE ]
I used a monocrystalline silicon solar cell (the kind that is predominatly matte brown and has no "shattered" appearance), a DMM set to read milliamps, and a mathematical formula that includes a wavelength value that takes into account the light detection curve of the solar cell.

Connect the DMM to the solar cell, set the meter to read milliamps, and fire the laser directly at the solar cell from 12" or more away. Note the meter reading. Wave the laser around a bit to obtain the highest meter reading.

For a 532nm DPSS green laser, this formula was used:*
(current in amps as shown on meter display)*1239.7/532/0.97 
*

For a red diode laser that emits at 640nm, use this formula:*
(current in amps as shown on meter display)*1239.7/640/0.97 
*

For a 488nm single-line argon ion laser, this formula was used:*
(current in amps as shown on meter display)*1239.7/488/0.97 
*

And for a yellow DPSS laser that emits at 593.5nm, use this formula:*
(current in amps as shown on meter display)*1239.7/593.5/0.97 
*
The resultant value is the laser's power in watts. A value of 0.04977 after this mathemetical formula was applied to the meter reading would equal a laser power of just a hair under 50mW.


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## hungryforlasers (Aug 22, 2004)

[ QUOTE ]
*Uisgdlyast said:*
sounds like it should be higher than 12... i'd try the other LED.

Also... i still cant get the cap off /ubbthreads/images/graemlins/smile.gif 

[/ QUOTE ]

Try opening up the back and shoving a pencil in it, the "guts" should just slide out. This worked for me. Look at the image below...


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## Crosman451 (Aug 22, 2004)

Just finished another one. With "holy grail" optimized crystal set, this pointer is kicking a**!!! /ubbthreads/images/graemlins/naughty.gif
















Only one in a hundred or so prove to have these exceptional crystals with all things aligned just right. /ubbthreads/images/graemlins/grin.gif


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## cybersoga (Aug 22, 2004)

104mw @ 614ma? I wonder how long it'll last!?


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## Crosman451 (Aug 22, 2004)

I had one pointer that I purchased from Dimitry in Canada a year or two ago. This one would always measure in the 100mW to 117mW range and even recorded a 127mW reading with it once. It lasted for several months, maybe less than 10 hours total use. Today it only outputs 24mW average but is still a good pointer.

Some never make it that long, but OH what fun!! /ubbthreads/images/graemlins/clap.gif /ubbthreads/images/graemlins/happy14.gif 

Here it is again...












First readings with new batteries were at 101mW, then 111mW, third reading 117mW, next 122mW pictured and then two separate readings after that of 130mW each!! /ubbthreads/images/graemlins/thumbsup.gif


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## Uisgdlyast (Aug 22, 2004)

wow.. how many greenies do you own, to get one that does 130mW must be luck(or like you said, one in a hundred /ubbthreads/images/graemlins/smile.gif )

Can you get a regular leadlight to go up to 600mA? I thought 500 was the max, and even then you'd burn the diode out. 
Also Cosman if you got time can you test to see if the green LED method of measure is accurate, there seem to be too many variables to make it really reliable


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## Crosman451 (Aug 22, 2004)

The green LED method... is it accurate or not. Who's to say. Like you said "have the time" which I really do not. Please don't take this wrong. I really have no desire to reinvent the wheel so to speak. With all the design and accuracy built into the commercial laser power meters it was a no brainer for me. In Coherent's own words:

"Our laboratory in the United States is unique in its ability to offer NIST traceable calibrations at 20 different laser wavelengths. All Coherent's calibration services are performed in an ISO9002 environment, and set the industry standard for quality and rapid turn-around".

NIST traceable calibrations...thats gotta be worth something..uh

The LaserCheck for $310-$320 is a bargin for what it does. "Just do it" take the plunge and you'll have a Laser Power Meter for years to come. /ubbthreads/images/graemlins/poke2.gif And you will KNOW, with out a doubt, what your pointer or other laser device is outputing.


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## The_LED_Museum (Aug 22, 2004)

Boy, I wish I had that kind of money. I'd buy one of those laser power meters in a heartbeat.

Let's see here... I have a number of red diode laser pointers (635-650nm), at least four green DPSS laser pointers (532nm), a green HeNe laser head (543.5nm at approximately 10µW), several red/orange HeNe laser heads and laser tubes (632.8nm), a complete HeNe laser (tube and PSU) that operates from 12VDC, an argon ion laser (488nm), and a yellow DPSS laser pointer (593.5nm) on the way.

None output more than 57.6mW (my SCE green has this output), but having actual power output values for my website would be nice. /ubbthreads/images/graemlins/crazy.gif


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## Uisgdlyast (Sep 6, 2004)

Well I gave up the look for my DMM and bought a VERY cheap one(<10$) to satisfy me.

In the DCA part i set it to 20m and get a reading of about .32(sometimes as high as .36 but i think its because the thing is cheap, or i accidently short something). So i'm guessing that its 320 mA, sort of confused me but them i figured to jsut move the decimal.

Anyways to my question, if i use a green LED and i put it on 2000uA will i need to move the decimal point at all to get a correct reading? I've never used a dmm for current before(maybe in school i did) and i think the one's i did use were like crosmans and jsut gave you a reading in the units you wanted


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