Odd driver problem

[matt09]

The Aixiz modules are pretty good although there is still a fair bit of light lost. I understand what your saying about the matches yeah, I finally managed to get one to light from about 5cm away after colouring it black, it took along time though. Can you explain the focussing with the smoke, what did you use to make the smoke in the first place, the laser?

I think I'll happily stick to 280ma with this one as I don't have anymore spares!
The lens is pretty much perfect with no fingermarks etc apart from the odd speck of dust
Tried it at night out the window for the first time and WOW, quite spectacular.

 

[IgorT]

That is quite spectacular.. Actually i think your laser is better than mine. I don't think i could make such a nice beam with it..

One question.. When you try burning stuff what distance do you focus the beam to? You can't burn stuff with the laser focused at infinity, like in your pic..

You have to turn the focusing nut so that the lense moves a little bit away from the LD. This should be easyer to do with an aixiz module, than with mine, cos with mine everything barely holds together..

Anyway, i then use smoke from a cigarette to see where the beam is at it's narrowest. Usually at about 30cm.

Then i put a match there and it lights up immediately. No waiting at all..

I can see, how it would be hard to find the narrowest point without any smoke, since no matter how small you make the dot, it appears much larger when you point it at something...

 

[Gazoo]

It's easier to focus on a piece of paper. Of course, doing anything that close one should be wearing goggles.

 

[matt09]

I focus the beam to the shortest range possible with the lens fully unscrewed when burning.
I will try something like that with the smoke as I don't have any goggles yet, I have been very careful so far though.

 

[IgorT]

I focus the beam to the shortest range possible with the lens fully unscrewed when burning.
I will try something like that with the smoke as I don't have any goggles yet, I have been very careful so far though.

Once you start burning something, you will notice A LOT of reflections coming even from a black surface.

A black painted piece of paper creates quite a light show while you're burning a hole through and a floppy disk reflects a surprising amount of light.

If you don't use goggles and look at something bright afterwards, you'll notice a blue afterglow. That means A LOT of the laser beam was reflected into your eyes.. Not something i would recommend..

 

[IgorT]

I focus the beam to the shortest range possible with the lens fully unscrewed when burning.

I haven't thought of this before, but on my laser, the difference between focused on infinity and focused at 20 - 30cm is very small.

I don't know how much you have to unscrew the focusing nut on an aixiz module, since i don't have it yet, but i think you might have unscrewed it too much..

The difference in the distance between the LD and the lense is minimal in these two cases. Less than a mm.

After you figure it out, i'd suggest, you mark the spots where it's focused on infinity and where it's focused at 30cm, so less guesswork is involved. I can't do this yet, since my optics are different, but when i get the modules, i will definatelly mark the spots.

 

[Gazoo]

IgorT,
Thanks for the warning concerning the reflections...I notice them all the time when burning, very silvery and very bright. I often wondered if it is the reflection off the mirrors in the diode we are seeing. Anyway, I would not attempt burning anything up close with no goggles either. The risk is too great.

 

[IgorT]

IgorT,
Thanks for the warning concerning the reflections...I notice them all the time when burning, very silvery and very bright. I often wondered if it is the reflection off the mirrors in the diode we are seeing.

Which reflections do you mean here? I meant the reflections coming from the spot you are burning.. No matter how black or how matte it looks usually, when you burn it, a lot get's reflected..

For example a floppy disk, that has a very textured surface and normally looks very matte, completely changes as it starts melting. The hole made by the laser is smooth and glossy, so it reflects a lot of light. (Specular reflections?)


But i have a different problem with my current laser - i hope it's just the optics - where, even when focused on infinity, a lot of light get's spread out, away from the beam..

If i go along the beam, and puff some smoke at it, i see the thin beam in the middle and also some weaker beams, that are spreading out more and more, the further away from the laser i get.

This forms a star like pattern on the wall and means, a lot of light is getting lost. I'm guessing you saw it in a pic i posted..


I'm hoping with better optics, i only get the dot on the wall.. Or am i wrong? Are such spread patterns usual?

 

[Gazoo]

If you turn your laser and the star like pattern turns with it, then it is your lens. I know you will have much better results with the aixiz module. It is possible the reflection you are seeing is the reflection from the magnetic disk inside the floppy.

Once you get your module, focus the beam on a piece of paper then sharpie the paper. You will definitely see the reflection I am referring to....but it is possible we are seeing the same thing.

I could be wrong, but I always thought it was the mirrors in the laser causing it...the reflection is not red. When you see it, you are at the focal point of the laser.

 

[matt09]

While I've been testing it, I've had the laser at the floor at the side of a desk and made my self 'hidden' round the front side incase of reflections. It's worked very well so far, lol. I can then stand up slowly over it check for reflections.

 

[matt09]

Ack, my 2nd diode just died but I have no idea why. All i can think of is that I ran it at too high power (280ma) for too long, although I had a big 120mm fan resting on top of it which kept it at room temperature the whole time. Is it advisable to lower the current to 250ma when leaving it on for long periods of time?

 

[Greyfox]

These diodes are usually rated for lower output, probably 140mW continuous. That's around 180mA current. Yes, most of them can be pushed harder and still work, but when you get up to the 250-280mA level (180mW optical), they heat up fast, and the risk rises just as quickly. The heat builds up faster inside the can, and it takes time before you can feel the effects on the casing.
A fan alone won't do much unless you have a good thermal connection and a heatsink with a large surface area. Even running your LD at 250mA, you should do so for only a short duration.
The other choice is to build up a TEC or a higher efficiency thermal transfer system for it. This will allow you to push it a bit harder and longer with slightly less risk involved.
My optimal suggestion would be to acquire a small amount of Arctic Silver (or the equivalent) thermal compound. Use this on the large ring of the diode in very small amounts, and do the same on the housing threads between top and bottom sections. If you can, get a small peltier chip (eBay) with a heatsink attached. If I'm going to push my lasers past 250mA for more than 30 seconds, I always have it attached to a TEC.

 

[matt09]

If you assume that nearly all the heat dissipates into the axizs module and they have a good thermal contact, then then temperature of the module isn't going to be much lower than the LD itself although the junction temperature may be higher. Only a very small wattage is being dissipated from the LD so putting a big fan over the module would provide ample cooling, verified by the fact it was at room temperature the whole time? Although the module is small, the large fan would have taken the thermal dissipation down to 5'C per watt or something meaning that with only 0.8 watts which the LD is producing, the temp of the housing would rise by only 4.5'C

 

[IgorT]

If you assume that nearly all the heat dissipates into the axizs module and they have a good thermal contact, then then temperature of the module isn't going to be much lower than the LD itself although the junction temperature may be higher. Only a very small wattage is being dissipated from the LD so putting a big fan over the module would provide ample cooling, verified by the fact it was at room temperature the whole time?

Actually, since the module is round and smooth, the fan on top of it does not do much good..

If you glued some heatsinks on the module (with fins) and then put a fan on top, this would give you MUCH better cooling, since the heat would have more surface area to escape through..


Otherwise it is possible for the temp in the LD to be higher then on the module, since the module is quite massive in comparison, and it takes time, for the heat to spread through it all..


You've seen my LD attached to the heatsinks.. Even tho it's in a plastic enclosure, it takes more than 4 minutes, for the temp to reach 40°C at 280mA.. Before it was reaching 45°C in less than 4 minutes, at 330mA, that's why i lowered the current..

But your diode may be different.. The one i'm using has prooven quite sturdy and durable, but maybe i'm just lucky...

 

[Gazoo]

Let's be clear on the facts. The GB diodes are rated for 130ma's which corresponds to a power output of 80mw's, at a temperature of 25C. We do push them to their limits, however I have not run one with more than 250ma's, and I keep my duty cycles short.

 

[BeamGlowEngineer]

Wow! had I know that you must discharge caps and install the LD before applying power to the circuit...I could have not burned up those first FOUR PHR803ts!

Guess that will learn me...lol

Damn. :-(