Would it be better to use a small buck driver for the first couple hundred lumens and then switch over to pwm fet?
Designed my own FET+1 driver for D10 headlamp. Circuit identical to D4, only indicator led and cap on output to reduce moon a little. I’ll go for Si4866BDY. Found it for 12 cents 
It would be a very efficient way but also quite costly and complex….Really the efficiency difference wouldn’t be all that big so return of investment would be fairly low.
I’d love to see it though.
this FET has no advantages electrically over the other mainly used MOSFETs, it is only cheap
high input capacitance,
Gate charge,
relative high RDSon,
bad thermal conduction to PCB
I bought recently pretty good FETs for 1 Cent price bug I can sell them here cheap
So can this firmware be used on a driver that uses a click switch that cuts the power to the batteries, so a half-press will change the modes?
Yes, that is what bistro is designed for.
For an e-switch you need something like Narsil or Anduril.
Is there a schematic available that works with Bistro? I’m trying to figure out how it works, such as if a capacitor keeps a residual charge during a half press, etc. And how the MCU remembers the last mode after remaining off for a while.
Thanks!!!
You will have to dig through the archives to find all the details on that.
But on a basic level, the OTC cap drains when power is cut and when the MCU turns back on it reads the remaining voltage. Based on that remaining voltage it decides if it is a half press or full press.
The downside to this is that it can be inconsistent, which is why a better option has been desired for some time. The idea option is to use a larger cap to keep the MCU powered for a few seconds after the light is turned off so it can measure the exact length of the button press.
Yes, there is an option for mode memory.
I’ve been looking through the archives for a couple weeks now and haven’t been able to find anything. Any clue what to search for?
A lot of the base design stuff like that was many years ago, we have just refined the ideas since then. Not sure what to search for, off time cap and OTC are ok but honestly since the design has evolved many times over the years, not sure you will find an all inclusive rundown.
The design we are using now is fairly simple to figure out though, the OTC cap is what measures the off time like I said above and the other pins are basic inputs and outputs for the different channels.
For the firmware side of things, that is another all game, it is open source if that is your thing but toykeeper and TomE are the ones that have made this work.
Hi I was trying to understand these drivers and I got lost, wanting to try which of these I can use to power an xhp70.2 led, with the possibility of ignition and charge control, I must be able to power with 2s or 3s batteries indifferently, let me know how I feel, thanks
2-3S means a Buck driver that does not use voltage difference to determine switching frequency like the LM3409 does
And charging needs also a separate circuit like TP5100, but a charging circuit can only charge one battery configuration not 2
I have build a few TA drivers successfully but three of my latest drivers seem to have a problem. If I use them on Turbo or with all 7135’s the flashlight steps down the brightness after a few seconds. One or two minutes later the flashlight will turn off completely.
It could be the driver is overheating with the AMCs but other drivers don’t have this problem. What could be the cause of this sudden stepdown and how can I resolve it? Any suggestions would be appreciated.
Sounds like voltage monitoring. Is it for 1S or 2S batts? Maybe the wrong firmware for 1S/2S? If it's 2S, you have to use the 2 voltage divider resistors, and of the right values, and the firmware to match.
turning off means you may have not the voltage divider used right or compiled not to read from Vcc
Hi all,
I am the owner of a Reylight Dawn 2.1 with a TA driver and modified Bistro firmware. I have noticed an oddity of this setup which is that the medium press does not take as long to engage when the light is warm. For example, when I put it on turbo for several seconds, I then only have to press for about a half or quarter second to get the medium press to work. Otherwise, I have to press down for over one half second. Any ideas about why this is?
This is normal for this generation driver. The cap heats up and changes the capacitance and thus the timing.
This has been an issue ever since the OTC cap was introduced.
There are methods now to improve this but they have not been widely used yet and the best method is to remove the OTC and go to a completely digital measurement system but no one has made the firmware for this yet.
Got it, thanks for the reply!
Is the TA-LDO 30mm the best choice for a 3s Convoy L6 with a XHP70.2 at 6v?
Thanks
If you want max power, then yeah while it is old it still works good, that is what I am using in my L6.
No idea if there is a newer/better option on the market now.