Kaidomain 50mW CR2 - inital review

I picked up my laser today, apparently it arrived at the Post Office on the 14th, but the lazy mailmen never left an invoice, I checked at USPS.com (It worked!) and it said it was delivered the 14th. If it wasn't for that, I wouldn't have known that the laser had arrived.

I love this little thing, it heats up evenly thanks to the copper housing, I've left it on for 2+ minutes without dimming, it's very nice and compact, I doubt I'll be leaving home without this laser again.
Does anyone know how to focus it, it has good divergence, but I' just wondering out of curiosity?

EDIT: 5+ Minutes of continuous usage, it heats up evenly, then just stays luke warm. This thing probably has a 95%-99% duty cycle. It stayed at a perfect TEM00 the whole time.

I may have just gotten a weaker laser (Or an overpowered DX 30), but it's about as bright as my DX 30, but I like my KD much more. I might buy a few to sell to some responsible friends for about $50 (A package of the laser, rCR2's, and charger+spacers).

IgorT said:

My second DX200 arrived today (the one which Rain at DX tested for me and said it was good), and of course it is mode hopping. What else. It's slightly better, than the first one, but not by much. It is obvious tho, that if this one had better heatsinking, it would work. Here the beams only split, when it gets very warm. (Probably scorching hot inside, since there is no contact between the module and the body, where it heats up the most!)

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The stupidity in laser pointer design is amazing sometimes. It would be so easy to make proper thermal contact between the diode and the body in these things, especially since they are electrically equal. But for some reason i fail to grasp the contect is always weak, often no more that just touching or via a tube and thread an inch or more away.

The KD has the same problem really, the diode is mounted in a tube, that is connect to the housing at the business end only. The circuit board is glued into a ring that screws into the main body. If they only made it such that the inner tube would screw into the ring, contact would be perfect.

But in the KD it at least does its job to some degree in the end, and the whole unit warms up evenly with little dimming. I've kept this thing on for 15 minutes a a time - the output goes down a bit as it heats up, but nothing compared to some of the (bad) DX lasers that turn into 1 mWs after a minute or two.

Benm said:

The stupidity in laser pointer design is amazing sometimes. It would be so easy to make proper thermal contact between the diode and the body in these things, especially since they are electrically equal. But for some reason i fail to grasp the contect is always weak, often no more that just touching or via a tube and thread an inch or more away.

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Yeah, a little more metal could solve many problems. It's exactly the same as with the drivers - everything required is there, only not connected..

The KD has the same problem really, the diode is mounted in a tube, that is connect to the housing at the business end only. The circuit board is glued into a ring that screws into the main body. If they only made it such that the inner tube would screw into the ring, contact would be perfect.

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The threaded ring could have a better contact with the massive body.. I mean, the KD50 body is so massive, it is ridiculous not to use it.. The ring at the top does good contact, but unfortunatelly, where it is not needed.

Oh, on mine, the ring is not glued onto the module. It is removable. And without the glue it still pushes against the module, so it does have some thermal contact..  But it could be a lot better.

But in the KD it at least does its job to some degree in the end, and the whole unit warms up evenly with little dimming. I've kept this thing on for 15 minutes a a time - the output goes down a bit as it heats up, but nothing compared to some of the (bad) DX lasers that turn into 1 mWs after a minute or two.

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I agree, the KD50 does a good job.. 15 minutes? What did you power it with? My output would drop a lot in 15 minutes, but mainly because of the battery voltage dropping - which is why i can't wait to get the AMCs..




Oh. i just got the second two KD50s today. It turns out, my firs one was average, which is why i liked it. One of the two i got today is slightly brighter at the same current. But the other is dim in comparison. Very dim actually. And it would seem it is getting worse.

Didn't have enough time to confirm the getting worse part yet, but it does not look good.

I measured the current, and when the good ones were pulling 280mA out of the battery, this one took 310mA from the same battery. So it is dimmer at a higher current.

It also gets quite warm. Something i didn't notice before, but mainly because i never took it appart immediatelly after using it. So the KD50 could also benefit from better contact with the body.


But i think i should return this one. It really sucks side by side with the other two. If this was the first one i got, i would probably be happy with it, and pleasantly surprised with the other two.. But this way it looks lame. Unfortunatelly i still don't have the thermopile, to check the actual power.

I noticed slight differences in the way it is screwed together, so it could be a thermal issue..

Nope... Looks like there is nothing i can do.. For some reason the third one has a slightly shorter spring, and the battery went in deeper, which i thought it is a bad contact somewhere..

But while measuring, i got a higher current, than with the other two. So that's not it. I also removed some of the glue, so the ring would make a better contact with the laser module, but it didn't help.

The funny thing is, that this one looks different from the other two, which have almost the same brightness. It has a glossy paint, while the other two have a matte finish. The difference is small, but i noticed it, while putting the switch of the good one onto the bad one. The glossy one is also more scratched up.


When i turn it on, it comes on close to the brightness of the first one but immediatelly starts losing power, untill it's hardly worth mentioning.


The funny thing is, they all work badly on the included 3V CR2 battery and the power is constantly dropping, as the battery discharges. I am using 3V rechargables, not 3.6V and they work much better with them. I usually recharge them when they are still above 3V, since the brightness quickly starts dropping at that point.


I could try raising the current with the bad one, but it already has a higher current, than the good ones. It would probably only get worse, or kill it completelly.

I guess i'll be sending two lasers back to china next week.

Any ideas on how to make a cheap lens cap for this laser?

IgorT said:

Nope... Looks like there is nothing i can do.. For some reason the third one has a slightly shorter spring, and the battery went in deeper, which i thought it is a bad contact somewhere..

But while measuring, i got a higher current, than with the other two. So that's not it. I also removed some of the glue, so the ring would make a better contact with the laser module, but it didn't help.

The funny thing is, that this one looks different from the other two, which have almost the same brightness. It has a glossy paint, while the other two have a matte finish. The difference is small, but i noticed it, while putting the switch of the good one onto the bad one. The glossy one is also more scratched up.


When i turn it on, it comes on close to the brightness of the first one but immediatelly starts losing power, untill it's hardly worth mentioning.


The funny thing is, they all work badly on the included 3V CR2 battery and the power is constantly dropping, as the battery discharges. I am using 3V rechargables, not 3.6V and they work much better with them. I usually recharge them when they are still above 3V, since the brightness quickly starts dropping at that point.


I could try raising the current with the bad one, but it already has a higher current, than the good ones. It would probably only get worse, or kill it completelly.

I guess i'll be sending two lasers back to china next week.

Click to expand...

Why don't you try soldering the click switch connections? Have you already tried that?

Doesnt sound good Igor.. i wonder if they switched to a differnt supplier or something (as the paint is different as well). I just ordered another one yesterday, and i'll make sure to have a good look at it when it gets here.

Btw, i can run it for 15 mins (and a fair bit longer) from a fully charged battery - but it does dim over that time. Dropping battery voltage does matter though, as you described the included CR2 primary cell does a lousy job. But then again most included batteries are pretty crappy (no matter the product, it seems), so i wont judge it on that.

bob1122 said:

Why don't you try soldering the click switch connections? Have you already tried that?

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The switch was the first thing i thought of, but i measured the current without the switch, and it was actually higher, than with the two good lasers.

I just noticed, that this laser doesn't only have a different colour, but is also a few milimeters longer.. The spring is shorter, than in the first one.. Looks like they cut it off. The funny thing is, that in the best one, the spring is the shortest, but the switch doesn't go as deep into the tail cap.

Looks like they just cut the springs off, if they think it's too long, for each laser, as they assemble them. But sometimes, they cut off too much, which causes the blinking at power on/off or even complete loss of contact, like in this one, before i adjusted it.


But of course, it just wouldn't be a cheap chinese laser, if it didn't start working all of a sudden.


I removed some of the glue under the threaded ring, that keeps the laser module in place. I removed very little. Just enough, so that the ring wouldn't be obstructed by it, and would only rest on the metal.

The end result is a laser, which is just as bright as the other two. But not only that. It suddenly started drawing less current! The current is now exactly the same as the one in the other two lasers..



I think it really was a thermal problem. The glue prevented a good contact with the ring. The laser module heated up, and the pump diode lost some resistance, which resulted in increased current draw, but lower output power at the same time.

Now, that the heat can flow to the body through the ring, it behaves much more similiar to the other two. It still loses some power as it heats up, but the difference, compared to the other two is much smaller.

It's not perfect yet, but at least i know it's not a bad one. I think, if i improove the heatsinking a bit more, it might get even better.



Now i need to remove some of the glue in the other two. The ring should only be touching the bare metal, and not be obstructed by the glue in any way. The ring should also be screwed in with the correct side touching the module. The side that is supposed to push as the module, has a 45° angled edge, which touches the 45° angled edge on the module. This provides the best possible thermal contact, other than adding a tube of course..

Benm said:

Doesnt sound good Igor.. i wonder if they switched to a differnt supplier or something (as the paint is different as well). I just ordered another one yesterday, and i'll make sure to have a good look at it when it gets here.

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Well, it's not as bad as i originally thought.. As i said above, the paint is not the only difference, the weak one is actually a bit longer.

But after some cleaning, it is not so bad anymore. Now it actually works pretty good. It's comparable to the first one, but still dim's a bit with heat. It's nowhere near as bad as i originally thought.


I don't think they switched the manufacturers. Maybe it was a leftover of an old stock. Or maybe it was a returned item and they shipped it to me. The previous owner might have thought it was dead due to the bad contact. The box was even slightly ripped up on one side. And it would explain the scratches on the tailcap...

Let us know what you get.

Btw, i can run it for 15 mins (and a fair bit longer) from a fully charged battery - but it does dim over that time. Dropping battery voltage does matter though, as you described the included CR2 primary cell does a lousy job. But then again most included batteries are pretty crappy (no matter the product, it seems), so i wont judge it on that.

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Maybe your 3.6V Li-Pos hold a certain voltage for longer, than the 3V ones i have. Maybe you shouldn't use the blue ones in the new one, as i just measured an identical current in all three, using the green 3V batteries.


BTW: After the clean up, it even works from the primaries decently.. I'm gonna do another comparison with the rechargables.


EDIT: This is funny.. Now the "bad" one is actually the brightest at power on, with the rechargables.. Need to see how the brightness lasts.
EDIT EDIT: OMG, it actually just stinged my skin! It can etch a floppy disk. Not really burn it, but it leaves marks!
EDIT EDIT EDIT: The strongest one actually makes a hole into a floppy!!! The "bad" one can do it as well, but slowly drops to a lower power.

WTF?!?


I'm definatelly not returning anything! Except the DX200 of course.


Ok, at the moment, the "bad" one is actually between the first one and the second one, which is the strongest.. When i power the "bad" one on, it is brighter, than the best one, but with heat, the brightness slowly decreases to slightly above the first one..

I have three good lasers! These are actually constructed pretty well, inside the module IMHO. The only problems seem to be electrical and thermal contacts, which can be fixed. The KD50 continues being my favourite green laser..

You have a floppy disk? Hahaha, I haven't seen one of those for a long long time.

My 50mW does sting skin but I haven't tried burning anything. It can't light a match though.

As for the top section that holds the diode and driver, how did you manage to remove that? I only have 1-2 screw threads sticking out here and I don't think it would be a good idea to rip it out with a wrench/pliers.

bob1122 said:

You have a floppy disk? Hahaha, I haven't seen one of those for a long long time.

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Yeah, i found them in an old box with my belongings, and keep them for testing lasers..

My 50mW does sting skin but I haven't tried burning anything. It can't light a match though.

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My first one couldn't light a match either. Not even through a magnifying glass.. With the second two, i think it might be possible. Maybe even without a magnifying glass. I mean, the best one made a hole in the floppy!

As for the top section that holds the diode and driver, how did you manage to remove that? I only have 1-2 screw threads sticking out here and I don't think it would be a good idea to rip it out with a wrench/pliers.

Click to expand...

As a matter of fact, it was quite easy to remove in all three.

I just grip it with my fingers and turn. It usually turns together with the driver, but it shouldn't. This is because of glue, that should be removed for best possible thermal contact.


Once you get it out, if you're lucky, you will also get the top ring out. You can then adjust the top ring, so that the driver sticks out of the head further, and the spring pushes against the battery firmer. This solved the contact and blinking / dimming problems in all three. If you don't get the top ring out, you can still simply screw the module in a little less deep, and then tighten it with the lower ring.


I wish i would have three extra of those top rings tho, since i could put two on at the same time for better cooling. It would be at the wrong spot, but better, than nothing.

Oh, about the pliars.. In one of mine, there were actually marks in the threads of that ring.. The manufacturer obviously already used pliars on it. The threads in the middle part of the body are wide enough, that they don't mind.

In one case, i adjusted the top ring too high, so that this lower ring stuck out too much, and when unscrewing, it got stuck in the wrong part of the body.. I used pliars to remove it. It doesn't take too much pressure, so it's not that bad. And i did less damage, than the manufacturer..



I can't wait to get the AMCs and the 3.6V CR2s, to replace the drivers in all three. I will also try to find a tube, to make contact between the module and the massive body. With these two mods, this is gonna be the perfect laser! It will be getting a little more current, but with the extra heatsinking, this shouldn't be a problem.

OK so I did remove the top section. It unscrewed with my fingers.

Unfortunately, it seems I removed the IR diode and the ring around it. I can see the 1064nm crystal (green), I think. So now I've lost a lot of power and I don't know how to realign it.

I don't know much about the inner workings. Which of the crystals is it supposed to be a bitch to line up? I presume the section between the doubler and this exposed green one which thankfully is undisturbed. What happened is that I removed the hot glue, and now I have the whole module out. The IR diode attached to the laser is exposed. The slip ring around this diode (the smaller one) unscrewed but I put it back in. Result being, that there might be a variation in the angle now.

Either way, I can put it back together. Does not seem like much happened, but I'll be getting another one of these which I'll leave undisturbed from my clumsy fingers.

Edit: Put it all back together after cleaning the lens. This is one of the strangest assemblies I have seen, a threaded ring screws into another threaded ring which screws into... another threaded ring! The driver is a bit shaky which I guess the hot glue accounts for. Looks like I'll have to reseal it.

Oh, and for the heatsinking, surely there is a better way? There is an air gap between the diode and the outer casing which a little Arctic Silver should solve quite nicely. I'm not sure about the larger air gap, perhaps solder or something (of course taking care not to fry the diode).


By the way, I would advise against screwing the ring out in that manner (to strengthen the spring contact). It will put stress on the diode and driver, which is the least we want. What I did was stretch out the spring. Note that too much will cause your click switch to stop clicking until it's loosened, and more importantly, make a round recess into the battery's negative terminal as if you hit it with a ball peen hammer. Again that would stress the diode a little too much, I think. I had no idea how badly designed this was, it definitely is a fine piece of equipment from the outside though.

I removed everything (the first time, just the exposed diode came out).

Yes, I did actually have the diode held on the driver and the lens assembly with crystals on the other hand.

Does it matter if the diode and the 1064nm crystal are not aligned correctly? I think I have a marked drop in output power now.

Edit: Yay! Full power now.

So what I did was place everything back in, and used the tip of a potato peeler to turn the diode screw ring tight (reasonably). Then I resoldered one of the diode pins because it was cold (the actual leg came off the join for this reason and caused the drop in power). Finally I stuffed some tissue in there to keep the driver nice and snug until I get some hot glue.

The glue is essential to this laser's operation, there is no doubt about that.

If the diode doesn't have a fast axis lense or a collimator, it matters a lot.. The fast axis should probably be aligned with one of the crystals diagonals, if it is uncollimated.


But i just accidentaly unscrewed the diode/crystal/expander assembly out of the brass module, so that only the collimator was left in it.


The crystals are glued directly on the diode holder, and the expander lens is glued directly onto the crystal holder.

I did not remove the glue, but i can't imagine, how the diode would become loose, if i did. I don't wanna try of course, but this is one assembly i really don't understand. How the hell do they adjust it?!?


If you remove the glue, the diode falls out?!? Is it not press fit into the holder, on which the crystals are glued?

If removing the glue poses a risk of the module falling appart, this is very bad news for the AMC conversion.. It means i'm gonna have to drive the "driver" through the AMC. And it will stop working at a much higher voltage, than it would, if i could drive the LD directly, effectivelly shortening the battery life..

Is it possible to remove the PCB from the LD without the LD falling out of alignment with the crystals?

If you had a bad solder joint, then that was the main reason for the drop in the power.. It probably just got worse, when you were unmounting it..

So youre saying, the only thing holding the diode in is the hot glue? Or is there something, that tightens it into the module with the crystals and the expander?


Congratulations on getting the full power out again! Since the diode and the crystals were in tho separate pieces, it's an amazing feat actually. After taking the DX200 appart, i can make it stop modehopping but getting it back to full brightness will require alignment in front of a power meter..



BTW... I think that my "bad" KD50, that has a glossy finish, didn't really have a glossy finish from the beginning. I believe the only difference is the length. The matte paint becomes glossy from handling. I think it was used a lot by the previous owner, before it was returned.. And then they sent it to me.

It does get very bright, but unfortunatelly still drops in power substantially, when hot.

What's even weirder is, that i discovered, the best one doesn't have ANY contact with the body, at the diode. It was all glue, and after removing the glue at the edges, the lower ring doesn't hold anything anymore..

There are substantial differences in how much the PCB sticks out of the head. This is the reason they cut the spring away. And maybe the reason there are different lengths. It could have something to do with the diode/crystalls alignment.

This is a very weird construction, and it's actually a wonder, that it works this well, without any mode hopping and all.

Nice to hear the bad KD also got to life, though i still find it amazing that many of these things need to be user modified in order to work properly

As for thermal improvment: i considered soldering the big ring to the inner tube, but that would likely damage at least the crystal set when left in place. I have no experience removing and re-aligning those, though it seemed to have worked out well for Bob.