FlexDrive Thermal Limiter?

[charliebruce]

HI all,
I was just wondering what the "symptoms" of hitting the FlexDrive V5's thermal limiter are. I built a 445nm earlier, set at 1.3A in a custom host. (Build thread will probably appear at some point...) When the laser's been running for a minute or so, the output will blink at about 2hz, until I get nervous and switch it off. When it's cooled off, it will have another minute of perfect operation. At that point the heatsink/head of the torch (single 18650) is warm but not hot to the touch. I suspect this is the driver's chip limiting itself due to excess heat, rather than anything else.

Is this consistent with what other people have experienced? Would smothering it in ceramic heat-paste be ill-advised (due to any conductivity etc)? I saw the coin sanded and cut to heatsink the driver, but I have more tight size constraints in this build.

Thanks
Charlie

 

[Coherent Light]

Sounds like it. When the flex overheats it will pulse, but also when the batteries can supply enough current it will blink as well. Arctic Silver is what most builders are using on there flex builds.

 

[Hemlock_Mike]

Try this --- A simple heat sink for the chip.

HMike

 

[charliebruce]

I'll try using some heat-paste on the chip's surface - hopefully, it will at least spread the heat better across the entire PCB. If that stays an issue I'll have to use some kind of heat-sinking, maybe a slither of Aluminium or something. Thanks for the quick reply!

Any other advice is also greatly appreciated - especially if anyone's managed to heatsink a flexdrive at 1.3A for "continuous" running (read: more than the 50s I currently get), in a 12mm diameter cavity (same as the Aixiz module). The size constraint in the build is the main problem.

 

[Coherent Light]

DTR has check His tutorials.

 

[Meatball]

Stick a penny or a dime on top on the chips, being careful that none of the metal touches circuitry. Secure with thermal paste and warp it up in electrical tape. Works like a charm.

 

[lazeerer]

I'll try using some heat-paste on the chip's surface - hopefully, it will at least spread the heat better across the entire PCB. If that stays an issue I'll have to use some kind of heat-sinking, maybe a slither of Aluminium or something. Thanks for the quick reply!

Any other advice is also greatly appreciated - especially if anyone's managed to heatsink a flexdrive at 1.3A for "continuous" running (read: more than the 50s I currently get), in a 12mm diameter cavity (same as the Aixiz module). The size constraint in the build is the main problem.

I would not just use thermal/paste/adhesive alone. This might blanket the driver and cause it to overheat more. If the heat is not being transfered to something it Will not do any good and maybe make it worse.

PM me if you want a Piece of aluminum that i can send you to thermal adhesive it to the back of the flexdrive that will fit in your 12mm cavity. On me

 

[Flaminpyro]

Howdy All
Yes you can use artic silver and attach thin coins to your drivers or you can get
some of these THICK solid COPPER heatsinks machined to fit to just the right part with a min amount of artic silver.
They will give you maxium heat transfer for you $ spent
and if you need something different than these something special I can do that for you also.
They are $5.00 each PM me if interested.

 

[charliebruce]

For anyone who is interested, I took the laser into school today, and used their IR camera to measure the chip's temperature. At the point at which blinking started, the chip's surface temperature hit about 135C. Definitely sounds like the thermal limiter to me..

Will post back here once I've sorted this issue. Thanks for all the suggestions and advice.

 

[ChrisNL]

Try this --- A simple heat sink for the chip.

HMike

why u using 2 drivers? to combine power?

 

[charliebruce]

"To combine power"?

Each FlexDrive will supply a fixed amount of current. By combining them in parallel you reduce the amount that each driver is supplying, allowing the diode's current to be higher than one driver can supply alone (a single FlexDrive with cooling could hit 1.5A or so, but beyond that you may run into major issues). Should keep them cooler and keep the current a little more stable too.

Full sentences, capitalisation and correct spelling are nice - if you make the effort to ask a question nicely, you'll find people are more inclined to make an effort with their answer

 

[ChrisNL]

"To combine power"?

Each FlexDrive will supply a fixed amount of current. By combining them in parallel you reduce the amount that each driver is supplying, allowing the diode's current to be higher than one driver can supply alone (a single FlexDrive with cooling could hit 1.5A or so, but beyond that you may run into major issues). Should keep them cooler and keep the current a little more stable too.

Full sentences, capitalisation and correct spelling are nice - if you make the effort to ask a question nicely, you'll find people are more inclined to make an effort with their answer

Yes i know, sorry for my bad language, i'll do my best next time (from outside u.s.)

And the parallel driver connection is nice i must say :yh: