Convoy's 17mm / 22mm driver for SST-40 sense resistor mod feedback :-/

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Barkuti
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Convoy's 17mm / 22mm driver for SST-40 sense resistor mod feedback :-/

This driver: https://www.aliexpress.com/item/17mm-22mm-driver-for-luminus-sst40-LED/32989372464.html

Made a bet with them and bought some. Since theoretically they can deliver up to 8A to the emitter without brakes, I modified one ∅17mm unit by swapping its R005 sense resistor with a stack of 2x R020s. An unmodified ∅22mm driver I have installed in a C8S does just a smidgen above 7.6A, while the modded unit measures ≈3.875A max (DC power supply amperimeter readings). So it works, but something is not there. The unmodified driver blinks 36 times when ramping, the modded one also does 36 but only the later 30 can be seen, there's a brief pause in the darkness when it starts from minimum. Also, the special “3rd” mode selection blinks remain Sick unseen and the 1% mode doesn't works (unseen too).

I do not have a good explanation as to why this happens, it shouldn't happen as V = I × R and hence the sense voltage remains Question constant. The special mode selection blinks are faint, they may be using the 5/36 or 6/36 ramping brightness level and this tells me if I stack more sense resistors they will eventually become viewable. But what about the 1% brightness level? Facepalm

Explanations?

 

Cheers Smile 

Edited by: Barkuti on 06/12/2019 - 10:07
BlueSwordM
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Wait, why didn’t you use a pure linear driver then?

https://www.aliexpress.com/store/product/17mm-Driver-for-SST40-4-modes-0...

That would make modifications much easier.

My very own high current Beryllium Copper springs Gen 3:
http://budgetlightforum.com/node/67401
Liitokala Aliexpress Stores Battery Fraud: http://budgetlightforum.com/node/60547

Barkuti
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That other SST-40 5A max driver with sequential mode change is just another story. Did someone try sense resistor adjustments with that one? The lowest mode could also stop working with it, even if just a little reduction shouldn't be a problem.

Anyway, what matters here is why in @#$% does this happen with this 8A weird firmware units. Sure there is a reason somewhere. I have another ∅17mm weird firmware unit waiting to be tested with less than 10mΩ of sense resistor, so we'll see. 

 

Smile 

id30209
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Just found this thread, how did it go? Was thinking to put 17mm linear and bump with resistor to 12.5A then place 90.2 in C8+...

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Barkuti
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id30209 wrote:

Just found this thread, how did it go? Was thinking to put 17mm linear and bump with resistor to 12.5A then place 90.2 in C8+...

The second ∅17mm 2x selectable modes current with ramping plus special mode driver I modified worked as expected. I swapped its R005 with a R010 + R050 + R200 stack, and it ended up delivering 4.75+A; used it to power a Convoy M1 with Osram 1mm² White Flat.

A 90.2? SBT90 gen2? Setting sense for 12.5A means very hefty increase in power dissipation at the MOSFET (roughly +50%), good luck with that. Try to increase MOSFET cooling somehow, thermal glue can help. Stars-922 here and there, Tian Mu grey (this one starts pretty liquid) or just find or use the one which you like best. 

id30209
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Thx Barkuti!

already got bunch of the thermal pads, silicone and adheaives. 

Most likely this one won’t last long but for fun it will serve the purpose.

Got inspired with my 4sevens S12 (SST-90), such a small flashlight and delivers nice beam but hard to open. Sad

 

Is resistor size 2010?

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Barkuti
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id30209 wrote:
… 

Is resistor size 2010?

1206 imperial.

EasyB
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Barkuti wrote:

That other SST-40 5A max driver with sequential mode change is just another story. Did someone try sense resistor adjustments with that one? The lowest mode could also stop working with it, even if just a little reduction shouldn’t be a problem.

Just bought a few of these to try to mod to 7A or so. Will report my findings.