445nm Laser is bright at first then dims.

supadots · Mar 14, 2013

I have a
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Diode + Lens: 445nm M140 Diode In Copper Module With Leads
& 405-G-2 Glass Lens (bought from DTR's shop)

Driver: 1.8A X-Drive V6 (bought from lazeerer)

and a Large Heatsink (milled by a great man that i cant recall the name of)
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when i hook up the laser to my power supply at 6.2 volts, it draws ~1.8 amps.

the laser appears bright at first then dims greatly.

what gives? i've had this project on the side for a long time now, but i want to finish and fix it. did i receive a bad diode or driver?:cryyy:

DTR · Mar 14, 2013

Diodes pretty much are good or bad. They normally don't die then come back. What is the driver supposed to be set to? Have you checked it on a test load? My first thought is it may be putting out a lot more than what you think it is.

Does it look kind of like what happens to this diode after it passes 2.2A.
Trying to kill a 445 diode with 2.1A of current.

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ryansoh3 · Mar 14, 2013

Can you measure the current going into the diode?

See if it's a constant 1.8A.

DTR · Mar 14, 2013

That is why I suggest a test load. I will never suggest putting a DMM in series with the diode unless you solder the wires to your DMM leads. See this.
http://laserpointerforums.com/f65/trying-adjust-output-help-80908.html#post1162498

ryansoh3 · Mar 14, 2013

Very good point, DTR.

Watch out for connection breaks that can charge up the cap and blow the LD.

supadots · Mar 14, 2013

I have not ran a test load yet. The driver I bought from lazeerer was set at 1.8 amps and draws a stable 1.8 amps from the power supply. The laser is bright for 0.5 sec then dims greatly. Yes like what happened in the video. Happens each time I power the laser. Bright for .5 sec then dim until I let go. Am I not understanding something here? The power supply I use to power the laser has a built in dmm. I am not using batteries, though, the same dimming happens when I do use batteries.

DTR · Mar 14, 2013

Can you take a picture of the driver. I want to see if any points are bridged.

supadots · Mar 14, 2013

DTR said:
Can you take a picture of the driver. I want to see if any points are bridged.

here you go. what do you mean by "bridged"?

Photo Album - Imgur <----the pictures.

supadots · Mar 14, 2013

DTR said:
Can you take a picture of the driver. I want to see if any points are bridged.

here you go. what do you mean by "bridged"?

Photo Album - Imgur <----the pictures.

EDIT: i am supplying 7.2v with my batteries (two 18350's) and when i supply the driver with 6v this dimming DOES NOT OCCUR. not sure why i was told that two 18350's would run this driver. anyways... what is going on? any alternative batteries to fit in my MXDL host? (now i feel foolish! this is what i get for not messing with this laser for a couple of months.)

DTR · Mar 14, 2013

Ok so take a look at this and make sure the two points circled here are not touching if so then the drivers regulation is being bypassed. @ 6V is it drawing the same 1.8A?

Cube777 · Mar 14, 2013

Just remember that buck drivers draws less current than they are supplying to the diode, so if it was set for 1.8A and it draws 1.8A from the power supply there is a good chance that the current that the driver outputs is likely much higher, thus causing the dimming that DTR explains occurs when the LD is getting to much current.

TheDukeAnumber1 · Mar 14, 2013

The last time I had the issue your describing I found out that I had a short somewhere in the host and there was actually a huge amount of current going through the diode. I had to trouble shoot the connections with my DMM and that solved the problem, diode has been fine ever since. Goodluck!

grainde · Mar 14, 2013

I once had a dodgy diode that did exactly the same thing. It would power up brightly for a fraction of a second and then go dim and this every time I turned it on. The diode was being run at 1.8 A and would get hot very quickly. I spoke at length to DTR about it, but we never found out why it was behaving that way. In the end I had to buy a new diode.

I can post a vid if you like for comparative purposes?:beer:

Edit: There were no shorts on the driver and at least two drivers at different currents were tried. Do you have a different driver to test?

supadots · Mar 14, 2013

now that i know what you are specifically looking at, here is a clearer picture. the two points do not appear to be touching.

http://i.imgur.com/WGtQWeL.jpg <------------

now here is a video of a a test of different voltage inputs. i tried to be clear as possible as to what was happening with the laser.

MOV08256 - YouTube

Blord · Mar 14, 2013

Is that a bench PSU in your video ? If you can set the current you can direct drive the diode for testing purposes. Just eliminate the factors that cause the problem.

A normal M140 diode can handle the 1.8A current without problem. They are dimming when the current is push much higher.
Sometimes the diode is a dude. They reach the maximum current at much lower level like 1A and when you push the current there is no gain.
At 1.8A it could be dimming.
I think you have a dude diode.

Lazeerer always checked the drivers he sells. So a faulty driver is very rare.

Cube777 · Mar 14, 2013

Does DTR check his diodes for "dudes" before he ships them out? I think I have received one of them

LED'd for no reason and now starts dimming after 1.5A....

445nm Laser is bright at first then dims.

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