Oshpark Projects

Here's a mouseover of the 17DD showing what's underneath

The diode could be rotated about 30* CCW to free up a bunch of space for fatter traces in & out. Also looks possible to pop in a via near the RST pin and add a resistor on the spring side of the board, if it turns out that's needed.

That's actually a very good point. Every FET based circuit I've ever worked on prior to this (so um...one lol) has had a 100ohm resistor between the MCU and FET gate. I think the reason I skipped it here was because the original SRK board never used one either, and I was lead to believe it work fine? That being said I know what it's there for so I should have included one regardless.

10k pull up on the reset pin to VCC will now be included on all my boards by default.

When I get the time to update some of these boards (and some sort of testing prior would be good) I will update the OSHPark projects.

Anyone who has ordered any of my boards and is experiencing problems, can you please PM me?

- Matt

The JB driver with the single 2SK4212 FET didn't use a resistor to the gate, and worked fine with any of the right firmware versions and before any mods using the stock unknown MCU and also after the piggyback 105C was added... it still works without the resistor on the new 46mm version, the only issue with that one is the noise from certain versions of firmware. Lack of a resistor shouldn't affect the smaller board if it doesn't also affect the larger one, I would guess.

17DD shows no change with RST jumpered to Vcc, still erratic mode switching with the luxdrv code.

Is there a pull-down resistor on the FET gate? Without one the FET could come on between the time the processor is powered up and it initializes the state of the output pins. Try something around 1K to 10K from the FET gate to ground.

None of the other boards have needed a pulldown on the gate using the same components.

I've tried jumpering various stuff at random: from B+ to the diode, and from the diode to MCU's Vdd, neither made any difference. But I then moved the jumper to go straight from Vdd pin to B+, bypassing the diode, and it now changes mode like it should, doesn't do that weird random strobe/morse code crap, doesn't change 2 modes when it should only do 1, etc. The diode isn't on backwards, could it just be a bad diode? I doubt it, since the battmon mode in luxdrv gives the correct number of blinks that matches the input voltage.

Try the pull-down…

Maybe not a bad diode, but it is a different diode, right? (than the one you use on the 105C)

Supposed to be the same diode, or at least functionally interchangeable. http://www.digikey.com/product-detail/en/ZLLS410TA/ZLLS410CT-ND/1767188

OK, progress, of a sort: the old standby version of luxdrv works properly with the diode removed & replaced with a jumper.

edit: Of course, the voltage monitoring is off without the drop from the diode, it gives 13 blinks for a cell with only 4.1v. But at least this is getting somewhere.

So all it does is remove the reverse polarity protection otherwise

I wonder if a switching diode would be better

http://www.ebay.com/itm/like/121300037210?lpid=82

See my edit above about the voltage detection. Also, it can't be programmed while the jumper is in place. The LEDs turn on when the clip is attached & plugged in. So obviously this isn't a solution, just a good clue as to what's wrong.

Does anyone know what the exact diode is on the Nanjg 105C? I have though I had finally figured it out about 6 times by now, still no closer than when I started, looks like.

If my memory is correct, I have seen the diode with S4 marking on it. That is 1N5819.

I tried a couple of different SMD resistors between the MCU and GATE, 100 ohm and 200 ohm, they both work and function fine. Did some searching and reading (still over my head) but from what I could gather this should ease the load significantly on the MCU. Definitely worth a shot for those of you who are having trouble.

For testing purposes I just bent up the leg and soldered the 0805 SMD resistor between the pad and FET leg. In future boards pads could easily be placed for a gate resistor.

I was testing this on the BLF17DD board BTW.

Are you using the same diodes as me, and did you have issues like mine that went away with the resistor?

e: In other words, is this a workaround to let it work with the wrong diode? If so it'd obviously be better to just switch to the correct diode.

I think it's the same one, which is the one from Digikey marked "41". It worked fine for me without any tweaks at all (without the gate resistor) using STAR 1.1 set to 0x21 (phase correct).

I wanted to test this out because DBCstm has had a few of these FET drivers die, including one that I built for him. Smoked the traces and on another one where he bypassed the traces the MCU may have died. Was thinking that our extra capacitors were just a bandaid for the true problem, which was excessive inrush current load when the gate is being charged. This is just a SWAG, I haven't taken any measurements with my fancy HF DMM or anything like that.

Don't mind the solder blobs, I've had stuff on and off a few times on this board. I went "tombstone" style.

Adding the resistor didn't break it, but that's different than confirming it fixes something.

I can't find that 1N5819 in the right size, the one on the Nanjg is definitely the same size as the SOD-323s I have here, is there yet another cryptic package size that's the same as SOD-323 but using a different name?

What I'm saying is that it may or may not fix your problem Chris, but it's worth a try; either way I feel like it will probably increase long-term reliability of the driver. Several have died of unknown causes that shouldn't have died and we have ruled out a few things that we thought were killing them, this is the next step in my mind.

The fact that jumpering over the diode fixes something tends to tell me that there is a power issue and maybe that we're asking too much of the MCU. Adding the resistor will decrease the peak load on the MCU. Try it and see what it does, it can't hurt. I think that we might have been right on the edge of working without the resistor but that doesn't mean it's a good thing.

1N5819 has different sizes of packing. SS14 is the size of SMA. I have this data sheet on hand.

I haven't heard anything about MCUs dying, who's had that happen? I don't think even a short to ground on PB1 will kill them, will it? I know I've done that before and they always worked again after it was fixed. I can't recall ever killing a tiny13. I've physically broken them, damaged pins and stuff, but never fried one.