I agree, the pin spacing is very tight. Fortunately only one pin actually needs to be separated from it’s neighbors. Still, if a person is a beginner at reflow soldering I’d say that this is not the place to start their journey. The same thing applies doubly to hand soldering.
PSMN2R4-30MLD vs AO3400? Single LED performance is what matters for this driver I think, and that should restrict us to looking at higher Vgs numbers vs triples & etc. At 3v Vgs it seems like we’d have around a >20milliohm difference in favor of the PSMN2R4-30MLD, which translates to maybe a 0.08v difference in voltage dropped over the FET. To me that looks like approximately half an amp. As you know, all this napkin math doesn’t get us very far. We’ll have to wait for them to be built and tested. (of course it should beat the 2502 by a wider margin)
You’re trying to make me rebuild the Texas Poker yet again, aren’t you?
I would order a stencil if I were to do this one, I’ve been finding the re-flow is so much neater with a stencil and Kester E256 paste.
Edit: I don’t have many (if any) 15mm driver lights. The TP is 10mm and I’m pretty happy with the way it’s performing. That said, I do have a little stainless steel light on the way that I believe uses a 15mm driver…
With stencils I’ve found it very helpful to have a piece of cardboard or something the same thickness as the board or mcpcb with a hole to drop the board into. This lets the stencil lay in place flat and is easier to keep aligned.
Anyone built these yet? I think I have 3 blanks in, but didn't build one yet.
Gunga - Sorry so late to reply, but I could I suppose, but not sure bout Canada shipping - if it's too costly. Haven't built one my self yet, but want to for a SolarStorm SC02 mod. With the LFPAK33, I would think I'd get more power (lower resistance) than the old style BLF 15 DD that uses that tiny IRLML2502 FET. Not sure if I have LFPAK33's though - have to order, and have to find out what would be the best.
Any ideas on the FET? Is the PSMN2R4-30MLD the best around? Crap - just saw RMM has them (MtnE LFPAK33). Added them to my cart.
Got the LFPAK33's in from RMM, so building one and trimming it down to fit nice in a SolarStorm SC02. Think it's a good match-up for this light. The SC02 here from fasttech is a nice quality small 18650 light, of course with an e-switch. The SC02 is a step-up from my normal e-switch EDC: the ZY-T11 clone from banggood. The ZY-T11 has the advantage of a taking a 26mm DTP MCPCB, and can fit a full size 17mm driver piggyback'ed in, but the overall quality of the SC02 is much better.
I know that wight is not around for quite around already…
But there’s one thing I don’t understand above. Maybe someone can help?
“I’d stick to 20-30v rated stuff”
Looking at the websites of various manufacturers I see FETs for 1S li-ion use that are rated at mere 12V. Wight would prefer a larger safety margin. Should we really avoid 12V FETs when manufaturers recommend them for use like ours?
wight was a real BLF innovator here, but has drifted on. Came back for a short visit a year ago or so, but that was it.
I think the 12V FET's would have to be looked at carefully regarding the other specs. Then of course, if you have 12V FET's, you just have to carefully stick with 1S setups. I don't think any of these FET's were explicitly designed for Li-ion use - we simply take advantage of what's out there.
For example recently I stumbled upon this MOSFET. Very small, with reasonable resistance. I’m not designing anything with it but I was suprised to see a “Power MOSFET for 1-Cell Lithium-ion Battery Protection” that didn’t meet wight’s guidelines.
Interesting. 18 amps is low for what we are using today. I guess the "protection" feature can help - think that's for reversing the cell. I know we use the diode to protect the MCU, but didn't think the FET needed it, or they typically have that protection? Not sure...
Yeah, I just can’t seem to get back into it. You never know though, it was a fun hobby and things could change. I’d like to pickup custom flashlights again some day in one form or another!
I suspect that I specified 20-30v FETs due to high voltage spikes. If you look around at older threads on BLF you can probably find someone (maybe comfychair, maybe someone else) posting scope images showing how high they can get. With long wires (inductance) and high currents the spikes are worse than otherwise. Better electrical designs can help mitigate the voltage spikes… it’s definitely possible to control a ~4v LED w/ a 12v MOSFET. I’d ask around and see if someone can link you to a thread showing scope images of voltage spikes on a DD driver. (I’d also ask around and see if there’s a better board to use than this very old one.)
I haven’t really vetted your FET selection at all, but note that the application listed on the product page is an “on/off” switch for a smartphone rather than driving an LED. There are many less-demanding FET applications than hotrod LED flashlights. At the moment I just can’t dredge up the right knowledge to tell you whether the gate protection diode is even something beyond standard on these FETs, much less a useful addition. It’s also worth noting that the part you are looking at is actually two FETs in one package… I suspect that you’ll be able to find much lower resistance / higher current single FET-per-package parts. Looking earlier in this thread, how about the PSMN2R4-30MLD?
I don’t have any design idea at hand with this FET, I was just wondering for the reason. And what you wrote here serves as a good explanation already. Thank you.
BTW, PSMN2R4-30MLD has lower resistance but only by 20% at 4.5V and it’s 3 times larger. At lower voltages I don’t have the exact numbers but quick look at the curves shows the same ballpark.
Hi wight! So good to see you posting!! Regarding those voltage spikes, DEL did some real improvements there with new designs, adding resistors and caps. We first used these design tweaks in the driver for the BLF Q8. He's a design engineer and scoped it as well. DEL is not active much now, but others took over and continued progress.
“This driver should sand down to 14mm w/out issue. 13mm is too much.”
Hope all is well with you…