Another Pulsing MicroBoost ?

[daguin]

I finished building a 445nm in a Cree C3 host. It uses a 14500 battery. The driver was set at a fairly conservative 850mA. I was having trouble getting it focused. It ended up being that there was something on the window. Anyway, as I was messing with the focus, the laser's output started to "pulse."

I thought, "The battery must be low." This is possible because my test batteries sometimes sit in the drawer for a long time between uses. I popped it into the charger and sat down to checkout the forum.

Fifteen minutes later, the light went green :wtf:

I thought maybe the battery or the charger had failed. However, when I tested the battery, it was fine. I popped it back into the laser and the laser began to pulse again after just a few seconds. I tested the battery draw and it was within normal limits.

I then thought, "Well I finally got a problem driver." I looked at it and could see no problems with the driver or the solder joints. I decided to look a bit closer to see if I could determine which component was causing the problem. I pulled out a 10X loop to look at the driver closely.

Everything looked good. Just as I was about to give up and grab another driver, the light reflected off of something. I looked VERY closely at the source of that reflection. I found a hairlike solder bridge between the negative solder pad and the component circled in red below.

This solder bridge was so small I could not see it with just my glasses or with my magnification visor. It required the use of a 10X loop and the light being right. I will admit that my 56 year old eyes are NOT as good as they once were, but that "stringer" of solder was minute!

I just grabbed a knife and cut the solder bridge. The driver worked (and continues to work) just fine after that. I think that if I had let the laser pulse for awhile and let the driver heat up, it would have probably just melted.

The moral of the story is that you should not trust or just "believe" that everything is soldered cleanly. If the driver isn't acting right, look VERY, VERY closely at it.

It saved me $25 :san:

Peace,
dave

 

[Morgan]

Definitely one to look out for. Thank Dave, that'll likely save some binned drivers and calls to the manufacturer!

Any ideas why this would make it pulse? I guess it'd take a few to be identified with this problem to say this is a definitive cure.

M

 

[00Giorge]

I had something similar to that happen at work, I am service tech and a particular piece of equipment kept doing things it was not supposed to do. I spent hours going thru everything, I checked all of the wiring connections, inverter and circuit boards and when I was about to give up I rebooted and saw a little blue spark I looked closer one little stand of wire that was soldered was touching a resistor. Removed it everything was working great! Thanks to Department of Energy I cannot say where I was or what I was working on.

My eyes are not that great either now that I am 50.

 

[Kevlar]

Good find Dave!!! And paying attention to detail :beer:

I always wonder when I read on here how so many people have problems with their builds or diodes that don't take their time.

I've always wondered how many people order drivers pre-set and just hook them up without checking that the solder blobs are done correctly or that they are in fact set to the current they want.

 

[BShanahan14rulz]

many simple DMMs come with a diode test feature. I like to use this feature to test for continuity too, since it makes an audible beep. It can be helpful for finding soldering errors, of which I make many. It can be hard to keep solder from going where you don't want it on something this small.

I really want to get a set of those "helping hands" with the magnifying glass someday... even if just for the magnifying glass!

 

[daguin]

Definitely one to look out for. Thank Dave, that'll likely save some binned drivers and calls to the manufacturer!

Any ideas why this would make it pulse? I guess it'd take a few to be identified with this problem to say this is a definitive cure.

M

The solder bridge was mine. It looked like the kind of thing you get when using "hot glue." Apparently, the solder just kind of "strung out" as I lifted the iron and made the contact as it "fell" back.

I have no idea why this would make it pulse. I am a professor of communication, NOT an engineer I am a fairly skilled "assembler" NOT an electronics guy. Maybe someone with a different education can help out with that question

many simple DMMs come with a diode test feature. I like to use this feature to test for continuity too, since it makes an audible beep. It can be helpful for finding soldering errors, of which I make many. It can be hard to keep solder from going where you don't want it on something this small.

I really want to get a set of those "helping hands" with the magnifying glass someday... even if just for the magnifying glass!

I test my builds at EACH step along the way. However, at the interim steps, I only briefly power the laser to make sure that it is still lasing. It took a few seconds to begin pulsing. I would not have observed this with my interim tests.

Helping hands are ESSENTIAL in this type of work. Get a set before you do ANYTHING else with lasers. Also, a magnifying "visor" is MUCH easier to work with than the magnifying glass attached to the helping hands

Peace,
dave

 

[Morgan]

The solder bridge was mine. It looked like the kind of thing you get when using "hot glue." Apparently, the solder just kind of "strung out" as I lifted the iron and made the contact as it "fell" back.

I have no idea why this would make it pulse. I am a professor of communication, NOT an engineer I am a fairly skilled "assembler" NOT an electronics guy. Maybe someone with a different education can help out with that question

- Ahh, I see, I was hoping it may have been a clue as to why others seem to behave this way. I suppose it still is but this was not a manufacturing fault and that's important to know.

- Yeah, but you're a professor! That means you should know everything! I guess I'll have to wait for an engineer to come along then.

Thanks Dave.

M

 

[Canuke]

I have no idea why this would make it pulse. I am a professor of communication, NOT an engineer I am a fairly skilled "assembler" NOT an electronics guy. Maybe someone with a different education can help out with that question

I do have "that" education, albeit about twenty years old and little used anymore

That solder bridge, being so tiny and thin, would act more like a new resistor in the circuit, rather than a dead short, and so would could subtly alter the characteristics of the circuit instead of simply derailing it completely. It's probably bridging into a part of the circuit that determines biasing or somesuch, which would explain why it didn't melt (biasing is usually voltage-based, and so that part of the circuit uses very little power by design).