Strange pattern with 405nm

[cheesemonster]

I'll start with a disclaimer: I am very new to this so I tried searching the archive but I can't come up with a decent description of the phenomenon so I apologize if this is a common problem.

I recently bought a kit for a 405nm 200mw laser and driver from ebay. I soldered the board and connected everything and got a nice, bright beam. After some mucking about with the focusing I managed to burn a thin cut into a piece of paper. After a while the beam suddenly dimmed and showed a pattern where before it had been uniform. Neither the diode or the lens had suffered any physical blow.

I have no idea what I have done so I don't know if I've screwed the diode and/or driver. The impedance over the points specified in the kit for calibration was unaffected.

Any help would be greatly appreciated.

 

[Cyparagon]

You may have melted the lens. A single speck of dust has the capacity to ruin optics at high power because it will absorb the energy and melt/crack the lens. Try removing or replacing the lens.

 

[Livinloud]

Looks like you got a special edition "all seeing eye"

Where can i get one of these? :banghead:

 

[Lethere Belight]

405 is violet and dim. You sure that's what you have?

 

[cheesemonster]

I removed the lens and got a similar pattern with less definition. I was going to post a photo but it has since quit emitting entirely. The board still has the same resistance values. It seems probably that I've buggered up the diode but I'm hoping to find out precisely how before I replace it.

The failure wasn't a sudden one; after dimming and 'fracturing' emission was intermittent.

Is there any measurement I can take to test the diode while separated from the board or would I have to make a new controller to test it?

Thanks for your help.

ps. Lethere Belight: Those were the numbers the supplier gave, I have no idea whether the output is true and my ability to judge the color is pretty poor: Just ask my girlfriend about our experiences in the paint department. :yabbem:

 

[Just4FunReally]

I removed the lens and got a similar pattern with less definition. I was going to post a photo but it has since quit emitting entirely. The board still has the same resistance values. It seems probably that I've buggered up the diode but I'm hoping to find out precisely how before I replace it.

The failure wasn't a sudden one; after dimming and 'fracturing' emission was intermittent.

Is there any measurement I can take to test the diode while separated from the board or would I have to make a new controller to test it?

Thanks for your help.

ps. Lethere Belight: Those were the numbers the supplier gave, I have no idea whether the output is true and my ability to judge the color is pretty poor: Just ask my girlfriend about our experiences in the paint department. :yabbem:

It's probably indeed a 405nm violet, which fluoresces into a bright blue on paper which you seem to be shining it on.

What you're describing seems to be what I experience a lot when I drive a PHR-805T too high, or if I get a specially inefficient diode. The diode goes LED (which we affectionately describe as "zombied") because it becomes damaged due to overwhelmingly high voltage or current (which is caused by one of several things, usually a poor driver or user misuse).

I think that whatever the seller advertised that diode to be was incorrect, and the diode was significantly weaker than they rated it to be. I think you're using a PHR-805T, which is recommended at 100mA or just over, and usually outputs ~100mW. If you could send us a link to the place where you purchased the diode and driver or send us info such as the diode's name/model and the drivers output we might be able to shed more light on the situation (pun unintended.)

Hope we can help you get this laser back on its feet!

 

[cheesemonster]

The diode and driver kit were purchased from
250mW 405nm Blue Violet Laser Diode Module Kit AR Coated Glass Lens | eBay

I don't think I overvolted it but I have to admit that I read a bunch of threads on this site explaining driver circuits and copped out by getting a kit. I adjusted the impedance on R3 to 6.9 Ohms but it did test at 7.1 once. Would this be enough to blow the diode? If so I need a better meter (cheap yellow thing).

I generally learn easier with something in my hands so I planned on cheating for my first attempt then using it as a basis for comparison for making further, improved circuits. The laser is intended for Groover's Pocket laser engraver project. If that works I'll probably cannibalize a printer or two and see what I can come up with for a larger device, maybe borrow and idea or two from the reprap crowd.

Looking at the flashlightesque enclosures many of the lasers on this forum has made me wonder how they are used. I would never have a steady enough hand to use them for cutting and they don't appear to be intended for communications.