Welcome to BLF
Wilkommen!
Will update OP later
Hmm ah OK thanks about 800 404 clarification 
There is always more to learn. I love it!
Would someone be willing to provide a FET primer… basic principles…what performance features makes one better than another, which well known lights use which FET and why, etc.
Cheers!
Please add me.
FET is a type of transistor that acts like a relay. Apply enough voltage to the gate pin and the resistance between the drain and the source drops to near zero. The kind we need has to operate with a gate voltage range as low as a single lithium cell (3-4V). This is referred to as RDSon for the resistance between the drain and source when on but many spec sheets only give RDSon values for 10V and 4.5V gate voltage and you need to infer from a graph what the resistance might be in our case. This is why members have tried out various fets in order to find ones best suited.
An FET and a 7135 are conceptually very similar in that they both can be turned on and off with a signal from the mcu but the difference is an FET is EVERYTHING THE BATTERY HAS when on and a 7135 is a 350mA fixed current. To get more you add 350mA lumps to get as much as you want. In either case intermediate modes are a percentage of the maximum. One problem with an FET is it’s hard to control it well enough to get a reliable moon mode from only switching a percentage of several Amps maximum so a second driver channel is used to control a single 7135 where one only need control a percentage of 350mA. Moon mode and any modes up to 350mA are done this way and higher current modes are controlled by switching the FET. Duty cycle is the percentage of time either on is on and is how the mcu controls the current. Pwm, or pulse width modulation is the method the mcu uses to manage that feat. Some drivers use a method where by measuring the voltage drop across a sense resister the mcu can monitor the current continuously and control it directly resulting in a constant current instead of pwm’d pulses from an FET or 7135(s).
What Scott describes is explaining the FET +1 driver that forum members designed. We’ve been using this style driver with a lot of success after it came out in the group buy Eagle Eye A6. The Bistro UI was intro’d in the X6/X5 Limited Edition lights, also a BLF Special.
Texas Ace is taking this concept further with his Texas Avenger driver series utilizing yet another forum member’s triple down design… three channels to help get higher efficiency using a mix of on 7135 chip for moom and very low modes, a bank of up to 8 7135 chips for the medium to higher levels, and the FET for high and Turbo.
Pilotdog68, DEL, ToyKeeper and others like Wight, mattaus, and Comfychair as well as RMM have done tremendous work here, changing the face of flaslights and how we mod em in ways that have had massive impact to this hobby and the forum.
Well, I'm not the one that could do the best job on a primer. Don't think you will find these specific high performance FET's in production lights, not that I know of, though I believe most production lights do use a FET, combined with other components. Higher end lights are probably always a buck or boost driver, or combo of both, but I believe they still do employ a FET.
This all started with the East-092 driver found in the HD2010, and small # of other budget lights. The East-092 driver was known for high amps, direct driven output. It could crank out high amps from the old XML LED's and clearly had a simple design from the small # of components. Then comfychair had a vision of getting/using the FET from the East-092 driver, and slapping it on a Nanjg driver so we could use better custom open source firmware, he called a Nanjg-092 here (his pics are long gone). Many of us built those from the instructions comfy provided, plus RMM was involved from the beginning with those. This is when the Vishay 70N02 FET was the hot FET to use, but soon went out of production and became unavailable. Then OSHPark came along, and couple guys started designing and laying out custom BLF designated drivers, many of which were based on the Vishay 70N02 FET while still available. wight soon became leader of the open source board designs, and alternate FETs (short for MOSFET's) were found and used. The NXP's became a standard, then Dale found the Vishay SIR800DP and slightly better SIR404DP.
Wow, been using/building these drivers so long I can’t remember what debut’d where!
Guess the FET+1 came out with the X6/X5 lights…
What a bunch of clever people can accomplish together. That´s awesome :+1:
please add an additional light to my username. thanks
Brian
BLF A6 first
I had originally asked for one. Can you put me down for a possible three more?
Two questions:
- Any idea on when this group buy will go live?
- How will we be notified when it does go live?
(Sorry if I’m being lazy. It’s hard to keep up with a thread that has as many posts as this one.)
Great work! I’m excited about this light. Thanks for all of the hard work!
So much great info and some history too. Thanks everyone!
What makes the 404 better than the 800? Less resistance? Lower gate voltage?
Yes will update the list later
When it goes live, topic title changes, a pm will be send and most likely the thread will see a lot of new posts so is gonna be hard to miss
Kind of like what will happen when you use this light- NOBODY will miss that action occurring (and some may even run to get sunglasses 
)
Phil
Might as well have them put the website on the side of the light, you KNOW everybody that see’s it in use is gonna want one…. like a specific link web address to go directly to the BLF Q8 on their site, something like www.thorfire.com/blfq8 on the side of the light, that way anyone that sees it can go directly there and get their own. That should boost sales. 
EDIT: THAT is NOT a direct link, not at the moment anyway, the forum highlights it and makes it look live but it was just off the top of my head. They should do it, though, really…
Yeah good idea gonna put it in the next email! Thanks
Or could put a QR code that people can scan in with their phones.
Well, SOME people could… I don’t have a smart phone.
Could you update my interested in for a total of 2 please?
I’m in for 1.
Thanks