BLF SRK FET Board discussion thread

Oh, and on all these drivers that keep the Nanjg's voltage divider layout (the 4.7K/19.1K resistors), the 4.7K is the one that has one end connected to ground. It's useful to be able to identify which goes where in case the silkscreen labels are missing/unreadable/incorrect.

Didn’t that issue get corrected in the V1 releases?
But yeah…the R2 is the one on the resistor bridge tied to ground

Good call sir

The silkscreen is fragile on the Oshpark boards, it's not uncommon to find they're partially scraped off in shipping since they just throw all the boards into a padded envelope. It's best to know where things go without having to rely on the potentially missing labels.

(also, if you can do it without needing the labels that's a pretty good sign you understand how the board works, and that's always a good thing) :)

Absolutely :slight_smile:

Doesn’t turn on, tried P2 & P3.
Any ideas?

Measure ohms between LED- and ground.

5.5 ohms

Well there's a tiny bit of difference between 'doesn't turn off' and 'doesn't turn on'.

Have you tried grounding the MCU pins 2 or 3 directly, not out at the SW pads?

If you temporarily jumper between LED- and ground, do the LEDs turn on?

Can you post both the source code you used, and the exact .hex file you flashed?

Do you have battery voltage (or close to battery voltage) on MCU pin 8? Ground on pin 1? If so, do the LEDs turn on when you jumper between MCU pin 8 & pin 6?

Double check diode (D1), might be in backwards

This was the problem, thanks.
Unfortunatelly, now it doesn’t turn off :weary:

The components were purchased from Richard, I didn’t flash anything.

If I recall correctly, I also sent you some other 15mm & 17mm driver kits. Is there any way the MCUs got mixed up between them? You can try to cycle modes by quickly cutting power like you normally would with a clicky switch to check.

Everything looks right in your picture, except for the backwards diode which you've already figured out.

I’m thinking of upgrading my SRK with this FET driver from RMM and am wondering what sort of max amperage I could expect out of 4x NCRB cells?

If I should expect 3A draw from each cell than this will be well worth the upgrade. However if I need to order 4 new high drain batteries to get anything over 8 amps than I won’t bother.

It will do more than 8 amps into 3x LEDs from just a single high drain cell.

Is that implying that I need to buy at least one high drain cell to get over 8 amps? :stuck_out_tongue:

Although 4 high drain cells are better than 1 (obviously).

The point is that I already have heaps of button top NCRB cells and would rather
not have to buy new cells to get at least over 8A.

Four non-high-drain cells in parallel will have less sag/higher current than any one single high-drain cell.

I want to put this driver in a sky ray king with 4 LEDs. I don’t have much experience with the tecnical side if drivers. What would some recommendations be for installing this driver In? I would also want it to be just a matter of trimming tabs connecting ± to led and switch wires then bam 7 well spaced mined with a nice moonlight and high high. :slight_smile:


I will mod my SkyRay King 8x Cree XM-L T6 flashlight with a new driver board.

Is the “BFL SRK FET Board” a constant current board? Or decrease the LED current then the accu voltage decrease?

Best regards from Germany.

This is the case: “decrease the LED current then the accu voltage decrease?”

EDIT: Please see this post by lagman or my elaboration on that post (#55) for more information.

Ah ok very interested post. Thank you very much. I think the 32x AMC7135 linear driver is better for me.