Lume1-FW3X: Constant Current Buck-Boost & FET Driver with Anduril1/2 + RGB Aux

I think i found the source of flickering issue. I decided to take out the driver and clean it with both acetone and IPA.

After cleaning, flickering is still there, but nowhere near as bad as it was. Now it completely stops flickering at 15+ ramp level (it was 35-40 previously). I wonder why it was dirty straight from the mail (I didn’t use flux for soldering) and which component is so sensitive to dirt.

Was your solder ‘rosin core’?

No, I was deliberately avoiding using any flux, because in past I had other flashlight drivers malfunction just from flux residue.

Maybe make sure to also disassemble and clean the tailcap contacts.

I recommend getting some Deoxit Gold for cleaning contacts.

Tailcap contacts seem to be fine. In my frustration to fix flickering, I already cleaned them and also checked if original driver would work and indeed it was working flawlessly.

I have 2 of these drivers installed in fw3x lights. Both have a very slight flicker at the lowest setting, but it’s unnoticeable unless I look very close at the light on my white table top.

Is the moonlight brighter on these than with the stock driver?

Yes

[Quote]Lowest moon mode is not as low as other 7135 systems - at the moment, it is a little brighter, but still usable. In fact, it is possible to reduce this even further, but the buck-boost goes into a pulse frequency modulated mode to save power / efficiency, and a flicker of about 100+Hz is visible. In fact, at lowest moon mode, a very slight ‘pwm’ of around 1kHz is present. This can all be removed, at the cost of decreased efficiency at low modes, so I think the trade-off is OK. Any higher and output quickly smooths out.
[/quote]

I would rather have less efficiency to get a smooth, flickerless, sublumen moonlight.

Looks like we need somebody to inspect it with good oscilloscope to see real picture ;))

Curious what loneoceans finds when he receives his… will be waiting patiently for that info :slight_smile: :beer:

Used my phone camera to capture the PWM

FW3… Stock Driver

NovaTac Lume1…

I can’t see flickering in either… I guess I’m not…….“sniff”……. sensitive……. enough :cry: maybe I need training… :blush:

Stock driver is first, Lume1 is second, both shot at 1/4000 shutter speed.

My FW3A with lume driver looks like this. In real life it doesn’t look like pwm flicker, but more like candle mode. I tried to record a video of that, but even on manual camera settings it doesn’t really show up.

@Kapsyd One of my older drivers used to flicker in the same manner you’re describing when driven at moonlight lows. To the naked eye it appears to be a “candlelight flutter”. The issue had to do with the switching regulator being driven at such a low current that the voltage changes on the feedback pin weren’t sufficient enough to provide steady output. The sense resistor wasn’t generating enough mV of voltage drop to properly provide a compensation ramp within the regulator, and the result was completely random and sporadic bursts of light that could be considered circuit noise making it to the output.

The resolution would have been to use a larger value sense resistor, but that causes serious thermal issues at high output and lowers the efficiency of the circuit a great deal. As with all engineering, it’s a bit of a balancing act.

FIASCO!!! So, I installed the Lume1 board. If your FW3C is a first generation, the board is flat on one edge, so the Lume1 is not a drop in board. Okay, fine. Filed it unit it fit. Also, the solder pads on the triple emitter board are in a different place.

Then, I looked at my stash of wire…mostly 28AWG. Close enough! I used my medium tip Weller soldering station. And of course this didn’t work. Solder everywhere. No problem; I’ll just unsolder the AUX board and get a finer tip. NOPE. Lost two of the VERY small resistors.

Buy the tools first, then build the thing.

On the bright side, my FW3C is not running the new board (minus the fancy AUX LEDs).

Hello all,

Thanks to all for all your feedback! While I'm glad that I've heard a good number of folks who have successfully got their driver working well, I also hear some challenges and problems faced by some other members. I'd like to apologize that the experience hasn't been as smooth as it could have been, and I really appreciate the feedback.

In all my prototypes, I've tried to make the performance of the driver as good as possible while keeping within some specific electrical requirements I set for myself, as well as additional constraints such as layout and cost. I wasn't expecting the product to be for sale like it has been, so I think I could have made the design a little more user-friendly for people who did not have the equipment for micro-soldering, as well as to have a more detailed notice about a fair amount of DIY required. For example, I hand solder all the components on the driver myself, so soldering on the wires for the Aux board is easy in comparison for me, but I understand not everyone has the same setup as I have! I do appreciate the patience that everyone has.

The key to soldering this in my opinion is to use very fine soldering wire, needle nose tweezers, and some sort of magnification if possible. If it helps, here are some of my suggestions for basic tools which will help in any sort of soldering:

On to the boards: I was finally able to get a few production Lume1 boards directly from Neal soldered up on my test bench, and I've been able to test the basic functions.

I'm glad to say that so far, everything actually looks good on my bench for the two drivers I've tested.

Component inspection looks good at first glance (I.e. it looks like all ICs are genuine), but I've also requested for a detailed BOM from Lumintop because they did replace some components despite the specific BOM I sent over (e.g. the sense resistor is the same value as the one I specified, but not the exact one I chose). So I'll give an update on that. However, the main components and large passives such as the big caps which are important, seem to check out OK at the moment.

Next, I was also able to test all main functionality and I did not see anything amiss. Specifically, some users seemed to have issues with the lowest modes, while others seemed to have no issues.

As contactcr correctly points out, at the lowest setting for the Lume1, there is in fact a small 'pwm' due to pulse frequency modulation of the buck converter. However, the performance I measured on my oscilloscope was in fact better than expected, with a current modulation frequency of about 2kHz only at the lowest possible ramp value (measured with a 100MHz Keysight current probe), but with very consistent levels (i.e. brightness is consistent so there should not be any flickering like a candle). I'll post more scope shots later on. Keep in mind that this is not actually PWM, and it should appear visibly better than an actual PWM at the same frequency. This modulation frequency very quickly increases before leveling out and should not be noticeable to the eye without moving the flashlight around quickly, and it certainly should not appear to be anywhere remotely like candle mode.

In addition, Kapsyd mentioned something about flux on the surface of the boards, and calipsoii talked about sensitivity of some part of the circuit - the general idea is correct. At the lowest current levels, the feedback the circuit is receiving is very small, on the order of tens of uV. This is a very sensitive analog signal and care was specifically taken in the design to ensure best physical routing around these sensitive lines. However, it is possible that any additional dirt / flux / contaminant on the surface of the PCB can contribute to leakage current and messing with this signal line at the low current levels, which can cause 'flickering' issues. The easiest way to see this in action is to touch the feedback components with a greasy finger when the driver is running at lowest mode, and you may see the output flickering! Even probing the circuit with a scope needs to be done with care since the scope probe adds significant capacitance to parts of the feedback circuitry.

That said, from the samples I got from Neal, the boards look to be very cleanly soldered, and I haven't been able to replicate this issue in my production driver boards, or even the pre-production ones from Neal.

Regardless, the components most sensitive to this are the op-amp (the smallest 6-pin component on the board, near the edge of the PCB surrounded by a bunch of resistors and caps), as well as those resistors and capacitors. The specific op-amp chosen has very high precision, very low input current and very low input off-set, so it's critical that this component is used and not swapped out. A small amount of contaminant in a humid environment can also introduce leakage currents.

For cleaning, I like to use a stiff small brush and isopropyl alcohol to clean boards. Something like this with the bristles cut down work really well, or a small stiff paintbrush: https://www.homedepot.com/p/Lincoln-Electric-Flux-Brush-KH589/202939867. I hope that could help alleviate the problems.

Meanwhile, I'll continue to validate the driver boards I have and I'll post more updates over the next few days (will be out during the weekend but back after).

Thanks to all again!

I’m very impressed by the driver and aux board; well done! And, yeah, we’re modding lights. It would be weird if it all went smoothly.

I also have a first gen FW3A and as soon as I opened the bezel I say the negative solder point on the MCPCB is not where the aux board wants it. I have not looked below to see if the driver sockethas a flat and requires sanding of the Lume1 driver but that is doable. The question is, is there a compatible MCPCB I can get, of the proper size and thickness and with the solder points in the compatible place?

MTN and Kaidomain should. Beware of polarity though, it might not be what is printed on the aux board masking. LED4Power is a no, Noctigon is a no.

Personally I would try scratching a new pad since I think only one is out of place. It looks possible but very narrow and probably not recommended after all

Sorry for the out of focus pic this is from when I installed Lexel board: