Recently ordered a couple of these: https://www.fasttech.com/product/4594600
They're going into S2+ class hosts with Samsung LH351D 4000K CRI90+ emitters.
A user reports the following tailcap current levels: 79mA for low, 875mA for medium and a high of 2.92A. Kewl mode spacing imho. Double click strobe.
Onboard PIC12F683 and… some sort of MOSFET in series with a 10mΩ resistor to the emitter cathode? This is all guesswork, of course.
Hope the PWM frequency is very high. By the way, couldn't we smooth out PWM signals by using a small inductor in series with the MOSFET here? Replacing that R010 with an inductor here, for example, and presuming 100+KHz switching frequency.
Any worthwhile feedback?
Was hopeful with no mention of strobe in the description, but that guy in the review and you both said it has strobe. Ugh.
Actually 3A current-regulated via fet, or just crowbarred-on with pwm for lower modes? Ie, will it be a steady 3A ’til the cell’s voltage drops low enough for it to fall out of regulation, or does max current drop with decreasing voltage right from the start?
Double click strobe is no problem if its period is short enough, imho.
As far as my wisdom goes I see no onboard inductor so, unless that black box to the PIC's right is a linear regulator I see this thing unregulated, but who knows. Lower modes are likely to be PWM, with 100(0.875/2.92) ≈= 30% duty cycle for medium and 2.7% (?) for low.
That big block looks like a FET. Now, it may be regulated via the sense-resistor (there are chips that do that) but I’m not sure if one of them’s on the board.
Or, it could just bang the FET full-on and rely on the resistor, springs, wires, etc., to limit current.
If you got a decent ammeter, you can measure tailcap current with a 4.2V just-out-of-the-charger cell, vs one that’s down to 3.6V or so. Below that, it may be low enough in voltage to pull out of regulation anyway.
One reason I’m not crazy about FET drivers is that they can be truly impressive with fully-charged cells, but start dropping off to nothing as they wear down, right from the start, like crappy 3×AAA lights.
Good point, Lightbringer. For high mode to be regulated, the PIC should be programmed to continuously adjust the duty cycle via sensing voltage drop at R010. This means high is also PWM regulated (wtf LoL hope the frequency is really high).
Post edit.-
The driver is linear, using voltage drop at the sense resistor to tune the MOSFET's VGS accordingly. So PWM free.
The discussed driver here is no longer available at FastTech.
