Oshpark Projects

Thinking about it a little more, let’s go for a bonus round. Instead of doing both jumpers, just stick your DMM on the protection diode and confirm that it’s dropping <0.5v. If so you are good to go on jumpering directly from BAT+ over onto the PWM pin / gate pin.

I did see your project but did not realise that the board could be used like this :-) Sooo, if you replace the bottom by a big +pad and a fat -ring, the one-sided 17mmDD board would be almost there, but the reverse polarity protection would be lost because there is no space for the diode? But reverse polarity protection is a very useful feature (I do insert batteries the wrong way every now and then), I am not sure I would like the board without it.

(always complaining )

That board has only 7135’s on the bottom. D1 is on top between the mcu and the FET.

Ok, sorry, I switched on my brain and dived a bit into the board, now I see: the protection diode is there. So do I understand correctly that the place where the trace starts that the MCU uses for the voltage measurement for LVP is different from the 105C, namely on the other side of the diode, and this must be compensated either by the firmware or otherwise by using a different R1? Can this also be solved by cutting that trace and make a bridge from the trace to the other side of the diode?

Yes, you understand correctly.

That change in the trace layout was to allow the voltage divider to see the full battery voltage even after a Zener mod so that lvp could be made to work again with just a change in R1. It means that the 19.1k value for R1 isn’t quite right for single cell operation though.

I assume the BLF15DD V3.0 OSHPark listing here: https://oshpark.com/shared_projects/lQUEtZcJ, has the wrong value for the R4 resistor? Says 100 ohm, should be 130 ohm? Can Mattaus correct that?

So the "Revision 2" has no limiting resistor while the V3.0 does. This is a little confusing between V3.0 and Rev 2 - different nomenclature - I'm not even sure if the rev # pertains, because one version has an option while the other doesn't. I wish rev #'s could be put on the silk screening somewhere, because I have mutiple board rev's all over the place... Are there any recomendations for R3 values if we want to limit current? Is anyone doing that? There's no BLF15DD discussion thread, so no source of info on this board.

The limiting resistor is just a resistor that goes between the FET and ground. Knocks the current down a little or a lot, depending on... everything. The idea was stolen from the generic little drivers like these:

R300 is the limiting resistor, 0.3ohm. Most of the time you'll just replace it with a jumper anyway. It's still direct drive, meaning the output is determined by the input voltage and the LED's Vf, the resistor just reduces current across the board. You could do the same by using a PWM value of less than 100% (and scaling the other modes down to match).

The value for the gate resistor at R4 should be the minimum value that lets the mode changing happen like it's supposed to, whatever that number turns out to be (that goes for all these drivers, no matter which size or version). 130 is just a conservative starting point mostly guaranteed to work. If it works with a smaller value, you should use a smaller value. If it works with none at all, you should replace it with a jumper. Using a higher value than the minimum required makes the FET's life much harder (slows down the switching speed, and generates unnecessary heat while the FET is in that not-on-but-also-not-off inbetween region).

Thanx comfy - planning on using a couple of these on those AA size cheap zoomies (https://budgetlightforum.com/t/-/21936), so don't want too crazy of amps.

1,000

Tom just an FYI, if you don’t want to use a limit resistor on that version of 15dd you must use a jumper otherwise the FET’s source pin has no connection to ground.

Personally I find the newer 15’s to be much better overall, I “limit” them by setting lower PWM levels, never liked the idea of the limit (sense) resistor.

Well, PWM's have their issues - so I'd rather keep 100% usable. I'm having a really tough time programming this board. The resistors to the right of the MCU are too close. Finally got one programmed by filing down the sides of the clip, but the other just won't program no matter what I do, and even the clip looks perfectly seated. Boy these are a PIA... I think I read others struggling with programming because of clearances - not sure if it was the BLF15DD or not. I'll have to remove the resistors and see if it will work then. Might as well try something because the board will be useless with no firmware anyway...

PWM only limits the average current, not the peak current that occurs with each PWM pulse. If the pulse currents are too high, you could fry an LED.

Hi Tom, you might want to pick up a Nanjg programming board and preflash the driver before you solder it in. The smaller drivers were too crammed for space to allow for clip clearance. The board will save wear and tear on your clip making it last longer for the drivers it will fit.

Thanx Scott! Actually I got the BLF15DD boards working! I did end up removing the 2 resistors, then I could program it. The other board I build up and could program. Think for me, I'd be ok with doing the parts reflow in 2 steps - seems to work ok for me. Actually I think I got those OSHPark boards - but didn't get a setup to use them.

My $3.xx "slim" mini CREE AA zoomie is sure zoom'n with a BLF15DD and a XP-L V6 on a 16mm Noctigon (sanded down)! Smile

I have a separate thread with oscilloscope images of the gate signal on the FET drivers, here: https://budgetlightforum.com/t/-/27485

With 130ohm gate resistor (PWM = 12) :

Gate resistor bypassed:

I'm a complete 'scope n00b, so any tips/suggestions are welcome, including hardware combos to test and what to measure.

CC, I checked out your thread. Good stuff and hopefully we can all learn more about these drivers. Would you like me to put a link in the FET board header? You might want it linked in the various FET discussion threads as well. Be nice to verify that the signal bounce is the cause of the erratic behavior and not something intrinsic to each different FET.

I am only able to guess right now about the weird bounce being the cause of erratic behavior, still have lots more configurations to look at before the fog will begin to clear. Specifically, what does the waveform look like on the SRK-DD boards, which have never had issues running correctly without the extra resistors. The overall trace length on the V2-up 17/20DD is longer than the SRK even when the 17/20's resistor is replaced with a jumper. I also have some of the first version 17DDs with the super-short trace and without the resistor pads, that would be an interesting comparison too. And then there's all the hardware variations and how they work with different firmware versions... like does the waveform look the same for fast-PWM luxdrv and fast-PWM STAR clicky and fast-PWM STAR momentary?

Your nanjg “east 92” should also be on that list.

Isn’t that what the BLF 17DD is, a re-do of the Nanjg “manual” build?

A purpose build nanjg east92