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The Kenometer at play...

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Well, I got my Kenometer today as well and I've just spent the night evaluating my various lasers with quite a few surprises, some of which validate the collective wisdom of this forum. :)

As for test methodology, I just measured the voltage of the batteries going in and shone it at the sensor from cold (20°C) for 2 minutes, noting when the max. mW reading was obtained and other anomalies. I then repeated the test about an hour later. Some I tested 3 times to be sure.

Here's a brief review of the meter: Fantastic! This thing is so sensitive it registers my finger reaching for the button on my pointer models. The zero-out pot is a blessing and the display is nice and bright. It was shipped in huge swaths of foam and arrived in great shape. I couldn't be happier with it. Thanks Ken!

Now for the ugly truths... I'll try to be concise:

Laserglow Vega-5 / Duracell C-Cells @ 1.48v - 35 sec. to a maximum 5mW, then fluctuates between 4 and 5 for the remainder of 2 min. This jives perfectly with Justin's readings of 4.7mW average on this unit. Once it warms up it's nice and stable.

WL Core 5mW / Alkaline AAAs @ 1.54v - Warmed up in 10 seconds and kept a consistent 5mW for the rest of the test period. Very stable apparently. (I'm surprised.)

DX 30mW / Alkaline AAAs @ 1.52v - 105 seconds to a max. of 33mW then stable around 30 mark. This laser seems to take a long time to warm up but once it gets there, it goes and goes. Just out of curiosity I ran it for 5 minutes and it was still above 25mW at that time. I did the same 2 min. test with an IR filter and still saw a max. of 28mW, so it looks like it's a pretty honest green.

RPL-Blue-30mW / rLIon 18650 @ 4.26v - This one takes a while to get going. Starts at about 15mW, climbs to a peak of 75mW :eek: then warms up and fluctuates between 28mW and 55mW. The power on this one is not very stable, but it kicks those beautiful blue photons out in waves. The power level seems to rise and fall within a 15 second amplitude, as if the crystals are trying to catch up or something. I'm not using this for lab work so stability isn't a big deal to me... 75mW max of beautiful blue is a big deal to me. Thanks Jack!

KD-50mW / rCR2 @ 3.43v - WOW. I always thought this was a good laser, now I know it. With fresh rechargeable LIon rCR2s it takes 25 seconds to reach a maximum of 77mW! Then it gradually drops down to between 45 and 50mW for the remainder of the 2 min. This laser is very sensitive to being held near the diode I found. The copper case is a great heat sink, but not so much if your fingers are heating it from the outside I guess). When I did the second test, I held it near the front and the readings were much lower. The third test later was a bit shy of the first due to the battery being used, but holding it near the tail cap made a big difference. That's good to know.

WL Pulsar 125mW / Alkaline AAAs @ 1.54v - 11 seconds to a maximum of (honestly) 125mW (!) then dropping down to 121mW at the 1 minute mark and down to 105mW at 2 minutes. Well, I for one was surprised that it could actually hit it's rated power, even if only briefly. This thing does suck the batteries though. The second test was lower, peaking at 115mW and the third test peaked at 105mW. After just 6 minutes of use the batteries were down to 1.49v, so I'd say for max. power, new batteries are a must. I have to admit that the beam was very stable with little fluctuation in power. It would just drop slowly at a linear pace as the batteries drained.
EDIT New Test: See YouTube video here http://www.youtube.com/watch?v=axQDsfdodXA for test results.

DX200mW - This one I did a few more variables with because so many people have asked me about this one lately.

1st test / Alkaline AAAs (NEW) @ 1.64v / 20°C - 10 seconds to a maximum of 170mW, then dropping to 153mW at 1 minute and 110mW at 2 min.
2nd test / Alkaline AAAs (USED) @ 1.54v / 20°C - 11 sec. to maximum of 110mW then 90mW at a minute and 87mW at 2 min.
3rd test / NiMh rAAAs (FRESH) @ 1.33v - 9 sec. to a maximum of 95mW, then 85mW at 1 minute and 82mW at 2 min.
The laser was getting quite warm, so I put it on my window sill with a thermometer and cooled it to 12°C to see if it would help. It did.
4th test / Alkaline AAAs (USED 2 Min.) @ 1.59v - 15 sec. to a maximum of 210mW, then dropping to 170mW at 1 minute and 145mW at 2 min.
The lesson I learned here is that this laser needs to stay cool to work effectively. It can produce >200mW but it overheats quickly and drops power fast. This echoes my experience with it, where it pops the first balloon instantly, then takes a while to pop a second. You're really only getting max. power for a few seconds and once it's warm you're lucky to get 100mW. It's best when it's cold, right out of the box with fresh batteries. I'm going to try heat-sinking this one to improve it's performance.
EDIT / New Test:
5th test. Alkaline AAAs (Energizer Titaniums) @ 1.6v / 10-15°C - See YouTube video of this test http://www.youtube.com/watch?v=0aWEnjYW7Lw achieved 240mW max. with "Chill-cell" cooling.

So, finally I know what I've got here and I feel pretty lucky that everything at least maxes out to it's rated power, if only briefly. This meter will add a whole new dimension to this hobby for me and really help me balance colours when my dichros finally arrive, so it's worth every penny. Get one if you can. Hope some others can benefit from these findings.

Cheers, CC
 

Kenom

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Or you can go right directly to my google checkout page and purchase it there.  Glad it works great for you.  I put a lot of time and effort into each one of these and even when they were done I was looking for ways to make them better!!! When I read ugly truths I thought the meter hadn't performed so I was kinda freakin out!! Good to see you actually have lasers that are within specs. that's getting to be a rare thing!
You might be interested in the graphing upgrade for your meter. it's not to costly. basically it's just a DMM with rs232 capabilities. I've got one's for $45


Link is right down there l
 l
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 l
 

IgorT

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Curiously_Coherent said:
As for test methodology, I just measured the voltage of the batteries going in and shone it at the sensor from cold (20°C) for 2 minutes, noting when the max. mW reading was obtained and other anomalies. I then repeated the test about an hour later. Some I tested 3 times to be sure.
It's great to see some measurements! Thank you for doing this..


I was wondering.. Did you perhaps measure the current of your DX 200?
I'm having some weird results with mine..


With fresh Duracell alkalines it takes 550mA at first, and splits into two beams immediatelly.. The current is constantly dropping, and when it falls under 500mA the beams join back into one..

With fully charged Varta 1000mAh Ni-MHs it takes 440mA at first, and again splits immediatelly. But in this case, the current is actually climbing! (due to internal resistance dropping from heat, and the batteries supplying a more constant voltage) When it climbs above 450mA the beams join into one..


With the last few tries with the Ni-MHs it stopped mode hopping completelly.. It's TEM00 from the start. But unfortunatelly i wasn't measuring the current. I'll do that next, to see if there is an optimal current..



Also, thanks for mentioning, that it helps to cool it down. I was asking about this for a while now, but never got an answer.. I think i'll mod mine to current regulation and better cooling, maybe even active TEC cooling, set to the optimal temperature..



From the beginning i was very unhappy with it, but the more i use it, the better it seems to get.. Is this possible somehow?

EDIT: I think i know what happened.. In the morning, when i got it, i was cold, so i turned the heating on.. That was when the laser worked the worst..
Now i just took it out of a cooler, and it works perfectly.. So i guess active cooling might really help.
 
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Kenom said:
Or you can go right directly to my google checkout page and purchase it there. Glad it works great for you. I put a lot of time and effort into each one of these and even when they were done I was looking for ways to make them better!!! When I read ugly truths I thought the meter hadn't performed so I was kinda freakin out!! Good to see you actually have lasers that are within specs. that's getting to be a rare thing!
You might be interested in the graphing upgrade for your meter. it's not to costly. basically it's just a DMM with rs232 capabilities. I've got one's for $45


Link is right down there l
Y'know Ken... The only PC I have at home is an old (very used) Dell laptop that I bought because some of my gadgets only came with PC software. (the bastards!) :D Other than that I'm all Mac at home and work, so I'd have no software or way to printout the data. (That laptop has never even seen the Internet since I wiped it.) Right now I'm using my digicam as a "visual logger". I just record the test then time and analyze it afterwards. It works for now and I can post a video if someone disputes a claim I make. Gotta have evidence, y'know...

Cheers, CC
 
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Alas Igor, no current measurements and I will check for TEM01 with goggles tonight. Your plan for TEC cooling sounds cool. (oh, that's corny... :D)

Keep us informed what you find with your testing about optimal temperature and current. Quite a few folks here would really like to know how to maximize and stabilize the power from this laser, as would I, now that I know what it's doing.

As for homemade reds, I have none. I just don't have the time to learn all that I need to in order to do it without racking up piles of fried diodes, and it's been so long since I soldered it's embarrassing. I'm sure those here who do make and sell home-made lasers are happy to have someone willing to pay for their mad skillz though... I'll leave the fabs and mods to those with the tools and expertise to do it right. (A big shout-out to Ken, Milos, Max & Bridge! Y'all rawk!)

Cheers, CC
 

IgorT

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Curiously_Coherent said:
Keep us informed what you find with your testing about optimal temperature and current. Quite a few folks here would really like to know how to maximize and stabilize the power from this laser, as would I, now that I know what it's doing.
I will post the results. I will be getting a power meter soon as well, so i will be able to see what mine is really putting out.

But i'm not trying to push it.. I only want to make it stable. I have verified, that it works perfectly when cool, and only splits when warm, and even then not always...

It's not as bad as it was in the morning, but i suspect that is because it's colder in here right now.
Makes me wonder, what will happen to all the happy new DX200 owners in the summer... (How long do you have yours?)


The least this laser would need is a more massive body. Quality lasers of similiar or lower power all have massive heads.. Since i'm building a tiny portable Peltier cooling system, i might try it for this as well.


I haven't taken it appart yet, but i found some pics on DX, where the circuitry is visible, and it would seem this laser has two ICs on the board.. I really wonder, what they do, and if a constant current source powering the internal circuit would help at all... It looks as if the power of the IR LD inside is regulated through a photodiode.. But in that case, i don't understand, why the current is dropping from Alkalines and climbing from Ni-MHs..

On the other hand, i don't know, how PD regulated circuits work exactly, or rather how this would show up on the current draw from the batteries...



BTW: Can yours light matches? At what distance?
 

chimo

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IgorT said:
On the other hand, i don't know, how PD regulated circuits work exactly, or rather how this would show up on the current draw from the batteries...
Most of the circuits I have seen on these use linear-type regulation. The current from the battery should be more-or-less what the LD sees. The magnitude of the current from the PD is used to provide regulation feedback. (The current from the PD is converted to a voltage and compared to a reference voltage - if it's too high, the comparitor reduces the drive to the LD's drive transistors.)
 

IgorT

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Curiously_Coherent said:
KD-50mW / rCR2 @ 3.43v - WOW. I always thought this was a good laser, now I know it.  With fresh rechargeable LIon rCR2s it takes 25 seconds to reach a maximum of 77mW!
How bright would you say the KD50 looks compared to the DX200, visually?


My DX is annoying me.. It's not stable enough, for me to be completelly happy, nor broken enough for me to return it.. They would probably say, there is nothing wrong with it..

Right now for example, it's at ambient temperature (around 20°C), and it won't mode hop on fully charged Ni-MHs.. It has a very nice beam actually. If it would remain this way, i would be very happy with it.. But it is still occasionally begging for a mod.


Oh, while you're at it, could you also give me an approximation of the spot size at a certain distance, so i can compare? Mine doesn't have a thinnest part of the beam. It starts out very thin and slowly spreads out. So i don't think it'll ever burn anything...


Thanks!
 

IgorT

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chimo said:
Most of the circuits I have seen on these use linear-type regulation.  The current from the battery should be more-or-less what the LD sees.  The magnitude of the current from the PD is used to provide regulation feedback.   (The current from the PD is converted to a voltage and compared to a reference voltage - if it's too high, the comparitor reduces the drive to the LD's drive transistors.)
Thanks Chimo!

I read about how the PD regulation works before, but i wasn't sure how this would appear on the current draw from the battery..

I mean, i assumed the current through the LD would be the same as the current draw from the battery, like you just confirmed. But what confused me was that the current was 550mA and dropping from alkalines and 440mA and climbing from Ni-MHs..


This is what i would expect from a completelly non regulated LD (direct drive with a resistor), not from a PD regulated one..


Shouldn't the PD regulation make sure, that the current (well, output power) stays the same, even with different battery voltages? In that case i would expect to see the same starting current and the same changes. Or am i thinking the wrong way?


I guess i'll have to put it on my PSU, to make sure what is going on, if the input voltage doesn't change.. But i better build a filter first, just in case..
 

chimo

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IgorT said:
[quote author=chimo link=1204695371/0#9 date=1204735461]Most of the circuits I have seen on these use linear-type regulation.  The current from the battery should be more-or-less what the LD sees.  The magnitude of the current from the PD is used to provide regulation feedback.   (The current from the PD is converted to a voltage and compared to a reference voltage - if it's too high, the comparitor reduces the drive to the LD's drive transistors.)
Thanks Chimo!

I read about how the PD regulation works before, but i wasn't sure how this would appear on the current draw from the battery..

I mean, i assumed the current through the LD would be the same as the current draw from the battery, like you just confirmed. But what confused me was that the current was 550mA and dropping from alkalines and 440mA and climbing from Ni-MHs..


This is what i would expect from a completelly non regulated LD (direct drive with a resistor), not from a PD regulated one..


Shouldn't the PD regulation make sure, that the current (well, output power) stays the same, even with different battery voltages? In that case i would expect to see the same starting current and the same changes. Or am i thinking the wrong way?


I guess i'll have to put it on my PSU, to make sure what is going on, if the input voltage doesn't change.. But i better build a filter first, just in case..[/quote]

The regulation scheme is definitely not perfect. Two NiMH is barely enough to run the LD so it doesn't really stay in regulation long (or never gets there to begin with). Here's some fun reading for you:

http://www.laserpointerforums.com/forums/YaBB.pl?num=1188440672
 
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IgorT said:
[quote author=Curiously_Coherent link=1204695371/0#0 date=1204695370]KD-50mW / rCR2 @ 3.43v - WOW. I always thought this was a good laser, now I know it. With fresh rechargeable LIon rCR2s it takes 25 seconds to reach a maximum of 77mW!
How bright would you say the KD50 looks compared to the DX200, visually?[/quote]

I'd have to say it's nice and bright in the dark, but at full power the DX200 beam can be seen in a lit room. I'll pick up some fresh Duracells and make a balloon popping, match lightin' video with the DX200 for you soon.

And thanks Chimo for chiming in with that great regulation explanation. (It's a bit over my head... :-[) Me, I'm going to go low-tech and create a passive cooling setup with the chill-cells from my wine cooler. ;D

Cheers, CC
 

IgorT

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chimo said:
The regulation scheme is definitely not perfect.  Two NiMH is barely enough to run the LD so it doesn't really stay in regulation long (or never gets there to begin with).  Here's some fun reading for you:
Thanks for the link. I'll go through it..


This would definatelly explain the results i measured and read about. If the laser was getting enough voltage, to actually regulate the power from the PD feedback, the current draw would have to stay the same, even at a higher voltage, right?


Since others measured up to 700mA from Lithiums, and i only got 550 (alkalines) and 450 (Ni-MH), this probably means, the laser is set to an even higher power. But even at these powers it has problems with overheating...


Maybe the best thing to do, would be to change the resistor, that determines, how the power is regulated from the PD feedback, and make the power lower.. Then the laser would be slightly less bright, but would at least give constant results over a broader battery voltage range..

EDIT: Or maybe the PD is not even connected, just like in the DX30 you analyzed...



I could also just replace the driver with a current regulated one and set it to a stable current, or simply power this driver from a current regulated driver. The output would be less constant, but still much more stable over the entire battery voltage range. I could simply use two 10440 Li-Pos in this case, and keep the same host.



Anyway, looks like someone, who is not as obsessed with perfection wants to buy mine, so it's possible i'll order another one, and hope for the best...

But i have to admitt, if the focus was adjustable, like in the KD50, i wouldn't care too much about the little beam splitting issue i have. If only the beam was parallel... Oh well, i can dream. :)
 




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