Left: red 'JB' single FET + toroid, PWM=3
Center: 3x XPG2, Nlite, 12x 7135, 'moonlight' mode
Right: 3-toroid SRK driver, PWM=3
Pretty snazzy! Any idea how many uH those toroids are?
The uH rating is less important than the current capacity, since everything that goes to the LEDs has to go through the toroid. Which of these would be least happy having 15 amps shoved through it?
I have not yet tried the little red one. Ones with fewer turns (less total length) or multiple or fatter conductors can carry more current with less resistance than ones with more turns or smaller/fewer conductors. As we know from selecting 'good' FETs, a few milliohms can make a big difference when the input voltage is so close to the LED's Vf.
The thing that has me stumped is, I haven't found any listings that allow sorting by number of conductors, and just looking through thousands of pictures on Digikey isn't really getting anywhere - everything I find that might be suitable is non-stocked. :(
You're right, they are all listed by uH (inductance) and amp rating. There are lots of stocked models on Mouser. The uH rating has got to matter, right? Isn't that the whole reason for using the toroid? Otherwise we could just stack a resistor with the same resistance as the toroid, but we know that the inductance is what's making the difference here.
Problem is that without an oscilloscope I have no idea how to measure the inductance.
All those shown have got to vary wildly in their uH ratings, but give similar results in calming down the lower PWM levels.
edit: Tested & working with a modified version of luxdrv 030b - ramping deleted, mode levels of 1,3,9,28,85,255.
Nice. I'm guessing the tab on the back would normally connect to a heat sink and ground. I take it, I'm guessing wrong?
Nope, not ground, the tab is for LED-.
G = Gate (the control pin/PWM pin)
D = Drain (negative wire from the load, here that's LED-)
S = Source (battery ground)
It goes between LED- and ground just like a 7135, except it doesn't limit itself to a fixed current. Whatever your cell can deliver is what the LED gets (minus a tiny amount from the FET's internal resistance, this one is around 0.0045 ohms).
Now that you say that, it does seem that the tab has an emitter wire on some drivers. Just seems like a good place to get the heat out. Thanks Comfy.
Yeah, glued on upside down with JB Weld, and flattening the legs and rebending them is probably a bit outside the intended design parameters, but you know... :evil:
At least it should be easy to solder a nice piece of copper to it.
It doesn't get hot though, on any mode. It might, in the other versions using the inductors since (I think?) in that setup the FET spends more time inbetween fully on and fully off, which is where FETs can get a little unhappy and start making some reasonable amount of heat.
A copper plate wouldn't help here anyway, since if the tab touches anything that could carry heat away the FET is bypassed altogether (LED- to GND).
Correct me if I miss something, but at say 5amps and an internal resistance of 0.0045 ohms, it will only generate 0.1 W, that will easily dissipate through the connectors.
So.. this is the thread that lead to the FET driver RMM is now selling?
Yes. Except I'm not selling it (yet). Comfychair's work was really what brought this all about in the first place. DrJones & Werner have provided excellent yet simple free firmwares for anyone to flash their own drivers.
So you are currently just selling the parts?
That's correct. I need to do some more testing before selling a complete driver, but it has been flawless so far with MT-G2 and XM-L2.
Is Werner's beta published anywhere? I've heard it alluded to in several threads.
That's the only way I will get a copy of it because he will demand $64K if I ask him for it.
minimo works with the momentary switch/FET drivers and minidrv with the clicky/FET drivers. luxdrv is probably better a better starting point for the clicky drivers, since it's got low voltage protection and the battery monitor mode, other modes can be changed/added/deleted.
I don't know what Werner's plans are for his version, I wouldn't want to speak for him. I tested several versions along the way on a range of driver hardware he didn't have access to to see how it behaved.
I received some 07N02's today. Yea!
I don't understand why folks aren't more excited about what is happening in this thread. To me, it's big news. That neat looking driver up in Post 152 would need a whole bunch of pain in the arse 7135 chips stacked up, if not for that FET. They would also rob some voltage (can't remember .1 something volts) and therefore more wattage too. This is just too cool.