Oshpark Projects

Looking back at the pics that Comfy posted, with a mouse-over showing where the traces are…that “star 2” position grounds the PWM leg. Why?

Where do I find information on what the “Star 2, 3, 4” are for?

The Star 2 is supposed to go to leg 5 of the MCU, not 6. Leg 6 controls PWM.


Borrowed this from Comfy earlier in the thread.

Might be so low that it “looks” dead but really isn’t

I have a cheapy XM-L that I flashed STAR V1.1 on a true 105C…in moon mode, it lights the LED, but just enough to make some light…you can look at the emitter and NOT hurt your eyes…any other setting and it glare blind yourself

Since the PWM of moon mode is like 3-5 of 255 the FET might not be able to open fast enough…thus no current flow

Correct, there's a mistake in the solder mask. Just scrape off another little spot above pin 5, there's a big ground plane above both pins.

Also, the old 105C 'napkin diagram' pic has the stars numbered from right to left, instead of left to right. I always count the dummy that goes nowhere as #1.

Hmmm, 28 posts since I last got on here.

Can someone summarize what I need/should/could change if possible? And on what boards?

- Matt


EDIT: I see now. Add provisions for two resistors on the FET gates on ALL FET based boards. If they fit....if they don't fit then what (thinking the Tiny15 just won't be possible)? I'll also fix of the P1/2 pads on the SRK FET driver. If anyone has been financially put out by some of these minor oversights please PM me and I'll replace your boards with new ones for free.

I'd like to see an in-line resistor pad (0805 SMD) for the FET gate, possible a pad for a pulldown resistor for the FET as well. Maybe two versions? I know that some would like the simplicity of using without any extra resistors or jumpers, but they seem to offer some benefit for some situations.

0805 resistor between GATE & GND (easy), 0805 resistor between PB1 & GATE (erm, not so easy, at least on the 17mm). I guess all of them using the TO-252 FET need those, the 46, 20, & 17mm.

17DD has the ground pad for pin 5/star 2 over pin 6 instead, just needs a tweak of the solder mask (might already have been done on the rev.2 boards, I haven't looked yet).

SRK FET board could really use a change to the switch input pads, something like this

I don't think the tiny little FET on the 15DD board needs the resistors, same as 7135s don't need them. I haven't pulled up the datasheet on that FET though.

Pfffft, stop that. We're participants, not customers. lol.

No, the FET will open at lower PWM values than when using 7135s. They usually don't work at 4 or less, the FET works all the way down to 1.

Matt, got any ideas as to why the SRK & Nanjg PCBs work without the gate/pulldown resistors, but not the 17DD? There's got to be some logical explanation. I think the only trace I didn't test with a bypass wire is the one from PB1 to the gate, but it's probably not that since the SRK one is the same width but about 4-5 times longer.

Mattaus, no worries man! We are all grateful (at least I am) for all of your hard work. You don't owe us anything at all.

I'll review the 70N05 boards tonight and see if anything sticks out as to why the 17DD is being such a PITA. I'm guessing no one has tried the 20DD yet?

I'll also make the others changes Comfy mentioned.

WarHawk, I had 2 star engaged to the PWM leg, grounding out the PWM. Once that jumper was fully removed it worked again.

BUT, I soldered leg 5 to ground and had the same 4 modes, moon wasn’t engaged by doing that. So I don’t know what’s going on there. Took that off and it’s still working fine in 4 modes.

Here’s some numbers for the crunchers out there. This test emitter is, I believe, an XM-L2 T6 3C on a 16mm Noctigon glued to a 1/2” thick copper insert in the HD2010 Aluminum pill. Wired directly to the star and run with my DMM using it’s 6” long 12ga leads with gold plated banana plugs…

Lo to High with rested cells

Samsung 25R @ 4.13V 2500mAh
.02, .43, 2.37, 5.26A

Sony C4 @ 4.16V 2600mAh
.03, .46, 2.45, 5.44A

Efest 35A @ 4.20V 2600mAh?
.03, .46, 2.49, 5.60A

Samsung 20R @ 4.20V 2000mAh
.03, .48, 2.60, 5.70A

Sony C5 @ 4.15V 2600mAh
.03, .46, 2.50, 5.44A

Test cell @ 4.20V 1500mAh
.03, .48, 2.55, 5.69A

So it’s consistent pretty much across the board, with the top performing cells showing their customary margin of lead. I’m charging those cells that were not fully charged, but I expect they’ll be consistent with the others. I don’t know why this FET driver is showing lesser numbers than I’ve gotten previously unless it’s the T6 itself.

Previous tests were also with a single XML2 on copper?

Looking at the FET 15 if the Attiny were shifted to the left then C1 R1, R2, and two extra FET gate R’s could be lined up(rotate C1 90 degrees and put the 3R’s parallel to it below) one below the other. This would also allow LED+ to be nudged left and be diametrically opposite LED-. This would put pins 2&3 closer to the ground ring for star connection.

EDIT - Just a suggestion but you might hold off on reworking the 15 until we find out what the limit is on that FET. The K4212 looks very robust and has an extremely low Rds of ~ 3mOhms at 4.5V and is 3.4mm x 3.4mm if we need to change that and might work for the 17mm board.

Digikey page a bunch of options.

That was with the same emitter set-up but no driver, straight direct drive. In that instance I was seeing High at 6.85-7.18A.

With the Qlite modded FET driver I was seeing 5.87-6.30A from these same cells. So it looks as though the BLF FET board might be running a bit lower than the Qlite FET board.

Edit: Just found notes where my C8 with the big copper pill from Buck and a modified Qlite FET driver pulled 6.66A from a 20R in a built light. Same light with an Efest 35A makes 6.61A and 1673 OTF at start-up, 1497 OTF at 30 seconds. This with an XM-L2 U2 1A.

You have the two new resistors on this one, right? Try jumping from B+ (or LED+, same thing) to the gate on the FET, see if it goes up when you do that. Also try jumping across just the resistor inline with the gate.

If it shows a big jump with the resistor bypassed it means the gate isn't opening fully when going through the resistor, we may need to look for a different FET that doesn't need the stupid resistors. I have a few of the 2SK4212s I can try, they have a lower gate charge spec.

Running the 18500 for ease of handling, I was seeing just over 4A on high with zero change both visibly and on the meter when I crossed the positive to the gate. Showing 2.7A on Med/Hi it did indeed jump in brightness and to 4A on the DMM.

Not sure about crossing or bridging the resistor, didn’t see any change there either.

Edit: Trying again to jump the resistor I touched the wrong things and it popped and smoked. I think it’s staying dead this time. I gave it a standing 10 count and they carried it off on a stretcher. It doesn’t look good.

No, wrong K4212. It's from NEC/Renesas, 2SK4212A. About double the Rds(on), but much lower gate charge. TO-252/DPAK package. The one that comes on the red 'JB-2013-11' driver. That exact part is discontinued/EOL, and the replacement sucks balls, specs nowhere near compatible for this low-voltage-overhead setup. The replacement would probably work fine in a different circuit. The old 2SK4212s are available in bulk still, but only as surplus NOS and only from possibly questionable vendors on aliexpress.

This one looks kinda interesting as a possible substitute: http://www.digikey.com/product-detail/en/AOD510/785-1481-1-ND/3603497

A little bit lower Rds(on), and Qg is much lower and closer to the 2SK4212 that started this whole mess in the first place.

Hey man, you know what they say: you can't make a driver without breaking a few omelettes... er, no wait...