LD-2 : 6Amps pwm-less linear driver - info and FAQ thread

Just read your test of post 121 with interest, it looks like a thorough job and gives a good insight in the possibilities of this FET/friver ! :-)

Hi

Do I understand correctly, that both of these resistors (marked with red arrows in picture) should be 750kOhm for 2S operation?

I plan to order some soon & i wonder if anyone have any information on how hard we can run them in the X6? I want to use it for my triple instead of the DD FET driver, with as much amp the driver can take i guess it is the 12A option right? Or is there a 10-11A option, i donā€™t know if the X6 XP-L triple even gets to as much as 12A but maybe the 12A really mean in that case, direct drive but with regulated modes?

If i would stuff the driver compartment with as much silicon cubes as would fit would that be enough? I donā€™t want to use the termistor on the mcpcb because i want it to run as hot as it can, and leave the drivers internal temp protection be enough to save the driver from overheating but not more.

Yes, two resistors of the same value but different values for each voltage level.

I think 12A with triple xp-l and DD driver was reported by some members,and since LD-2 has similar parasitic resistance, 12A sounds fine if you really want max. lumen.

Nice :slight_smile: Thanks

I have the driver set up for 6V with moon parts installed and activated in a heavily modified 502B (extra length for 2x 18650 and 10 copper fins). The driver and ntc are fully potted and ground is bridged to the host pill(also copper)with copper wire and solder. All 4 modes work(moon is just a lower low since I didnā€™t change the moon R) but switching is a bit inconsistent, sometimes more than one half press and has to be brief. After the light heats up in high mode half press no longer changes modes. It stays in high until I turn it off and let it cool, then it functions as before. It does not go into overheat shut down or even ntc step down and this occurs before the fins get uncomfortably warm. Itā€™s not a floating P60 design anymore, the new copper pill screws into threads cut into the copper fins. Is this an issue with an off-time capacitor that has been stressed?

That sounds like ntc isn't connected the right way(are you sure you connected it to correct pads?) and/or even more possible is that there is a short between ntc +pad and off-time capacitor, which is right next to the ntc +pad.That probably happened during ntc +wire soldering. If this is the case,then off-time cap has ~200kOhm parasitic resistance when cold,which would explain why tap must be pretty fast to change mode;when flashlight gets hot that parasitic resistance drops to ~115kOhm,and explains why you cannot change modes anymore - parasitic resistance causes off-time capacitor to discharge much faster than usual, so driver sees that as turn off.

But since driver and ntc are potted,I'm not sure if it's possible to fix that problem.

It is a good idea to check if everything works OK before permanent seal.

I soldered both ntc and led wires from the spring side so bridging should not have occurred but nothingā€™s certain when I solder. The potting is somewhat removable and not bonded to the pill only the driver so Iā€™ll check that. I presume the cap is between the mcu and gnd at the top of the board in your picture(trace running straight up to board edge right of led-). Thanks for giving me some things to check.

Heat and a fancy UI do not like each other, so it appears again.

Well,maybe some solder leaked through the pad hole and cause a short,I'm pretty much 100% sure that there is a short between that pad and off-time cap. Capacitor you're describing is the off-time cap.

I assume you're talking about off-time memory issues on various blf DD/7135 drivers when they got hot,but this doesn't happen with LD-2,and LD-2 runs much hotter than DDs in some cases,becasue it's linear driver.After all,you did a real torture test on LD-2 prototype, in which driver shtuted down due driver overtemp. several times (which means whole driver was hotter than 100C,much hotter and any DD driver could be),and I din't remember you report any off-time memory issues.

Yes, I was referring to the BLF-A6 driver, and was a bit quick to extend it here, I admit. I now read it might be a soldering problem.

I did have some erratic behaviour on the LD2 prototype (as reported) but that was not UI related, looked like something with the FET, it was not repeated inside a flashlight.

If I remember correctly, extreme power dissipation (6-7W I think) without cooling was the cause.

Anyway,I'm sure Rufusbduck's problem is ntc-offtime cap short,because symptoms match theory perfectly.

You nailed it. Not a solder short but a single strand of the ntc didnā€™t go in the hole. You can see it here sticking up from the base of the black wire like the boner that it is. Couldnā€™t see it with a naked eye. Fixed that and then toasted the op amp trying to test it with a 6V battery and test leads. Iā€™ve got a new op amp on it now and it seems to be behaving but I canā€™t run it full power for long without the led in the light and that means re potting, re installing, and re crossing my fingers.

Nice find and fix RBD. Fingers crossed.

All 9 of ā€™em. :wink: Iā€™m lovin/hatin this light more each day. Like bad hair, it grows on you.

@led4power - Bravo! Those are some excellent deductive reasoning skills. You certainly know your product well.

Any idea why the light flashes approx 5 secs after switching on high? It flashes 4 or 5 times then steps down to low.
Xhp70, 6 amps. The other driver worked fine but for the fact I messed up the soldering and it only had one mode so I changed it.

I had a similar problem Here

Possibly a short with the NTC
But got it working fine after cleaning each solder joint up