Is it possible to identify and remove a PWM controller from a circuit?

Flashlight Modding and DIY Parts
12

Ok, point taken.

Here’s a link to some new pictures of the back of the board: Imgur: The magic of the Internet

Does that clear anything up?

Also, would it be possible to lower the current consumption without adding any extra components based on whats there already? It’s around 2 amps on an eneloop AAA at the moment for roughly 130 lumens OTF, this is a bit high for a single mode light imo. But I can deal with it if it’s not easy to lower.

13

can you put up what is on the two six pin chips? I might be able to use some of my google-fu to help… I googled CFC3W, but all I got was chinese gobbledygook.

edit: upon closer inspection, I don’t think it has an identification code.

14

You need component changes to change drive current.

Please set the light on medium and post voltages for each pin on each SOT23-6 chip. It will take you 15 min and make the project much easier.

I think it’s fair to guess that the chip on the inductor side is the modes chip.

As a side note to Cereal_killer and anyone else with confusion on the subject: just because the chip controls things like modes, LVP, etc does not make it an MCU. I’m sure we will not classify this one as an MCU. It’s a dedicated, non programmable chip. It probably integrates modes + a 20mA LED driver which is instead used to control the boost circuit.

15

Thanks for keeping up the help. I’m really not sure how I could post voltage measurements for the pins though tbh, I’ve only got the light to run with it assembled so far as I need the negative path to be intact. If I use a DMM to make the connection and get it running I won’t have any hands free to measure voltage on the pins. I’m not sure how I could access them with the cell connected either, as they are so small and would be tucked under the positive end.

I don’t mind going with a ‘best guess’ connection on the inductor side and getting it by trial and error, as long as there’s not too high a chance of permanently destroying the circuit…

Oh, and yeah the component on the inductor side has no markings. I didn’t have any luck with the markings on the other components either, apart from the 2300 one which I think I found on aliexpress but looked unrelated to PWM.

16

The process is simpler than you think. Go get an alkaline AA. Solder appropriate length wires to it (5-10in, enough to get it out of your way). Also solder some wires on the LED’s MCPCB (long enough to get it out of your way, preferably under a sheet of paper or under a paper cup or whatever). Solder the LED wires to the circuit, then solder the AA to the circuit. Now you can work on the PCB with your DMM.

You’ve got 3 options for mode switching:

  • Do what I described above and be sure you’ve got it in the right mode before final soldering
  • Cutting a wire to the AA, stripping the ends, and tap them until it’s on medium/whatever - then twist them.
  • I’d just wire in a switch.

Do not power up the driver without an LED attached.

17

Ok, I have virtually no equipment or workspace here tbh (I should be able to find a few wires more than a couple of inches…) but I’ll give it a go.

What do I touch the negative lead of the DMM to whilst measuring the pins?

… Ok, this might sound a bit amateurish (which is fair enough because I am one), but I’ve run into a few simple problems. Firstly, my wires aren’t really long enough to get stuff out of the way, secondly, my solder won’t stick easily to any of my primary cells, and I actually only have about an inch of solder left atm so don’t want to waste it up in multiple attempts and leave none for reassembly. Thirdly I don’t currently have any spare emitters to test with, the only available one right now is the neutral XP-G2 that came with the light on a tiny board which offers effectively no heatsinking, and I don’t want to overheat the emitter doing a test.

I don’t want to give up having come this far, but am considering just extracting the emitter (fantastic tint) and replacing it with a standard XP-G from another light before gifting it to someone who won’t care about either PWM or tint but will like a small stainless steel light.

18

just to clarify/add onto wights post: make sure to keep the led cool, keep it mounted in the head of the flashlight, or on a separate heatsink.

as to where you should stick your probe for ground: I think any ground will work in this case, but don’t quote me on that. battery neg., driver ground ring, chip ground. Just go for what is easiest.

19

Keeping it short here, I’m on a mobile device :

  • You’re almost certainly going to need more solder than that.
  • musicmagic is right about GND, get it where you can. I usually do it at the driver board, that way both my hands and probes are in the same place.
  • you may just have an iron that is not high enough wattage. Don’t worry about it, use a rubber band instead.
  • rob long wires out of whatever: old computer cables, old power cords, old 9v DC adapters, etc
  • musicmagic is right about the emitter as well. Install it in the head and keep runtimes short or use a fan.

Also don’t give up now :wink:

20

But... isn't there some way to figure this out that doesn't involve tools, supplies, or effort? (sorry, couldn't resist, just kiddin' :))

21

Ok, I applied a bit more effort and some elastic bands and have got an answer!

Readings for the 6 pin component on the B+ side, clockwise from the top left, with the writing upright on the component itself, were:
1.42, 4.91, 1.42, 1.43, 0, 0

Readings for the unmarked 6 pin component on the other side, again clockwise from the top left, (with the inductor to it’s right) were:
0, 0, 0, 0, 4.92, 0

I really hope this can tell something useful now that I’ve actually got it to work.

22

Good work. (but) This was definitely in Medium?

23

Oh, sorry, this was in low mode. I found a spare LED but nothing mounted to a heatsink and no way of properly doing so so I just ran it in lowest mode. That still uses PWM but at both a lower freq and with a smaller % on cycle. Does the reading need to be in medium?

24

Nah, just not on High.

I’m a little confused at the moment about that chip on the inductor side. All those zeros…. Hopefully I’ll have a moment of clarity soon.

25

Would you mind sharing what you’re looking for? What would suggest a PWM related pin?

I’ll try retaking the readings as well instead I made a mistake first time, I did do it twice already though to confirm.

26

I believe that your measurements are not correct. You said that you measured the unmarked chip starting clockwise from top left (with the inductor on the right). Using your numbering shouldn’t the value for 5 and 6 be the same?? I see that they are sitting on the same trace in your pictures.

Also, please determine LED voltage while running in Low (the mode you took the other measurements in).

27

Multimeters do not always give consistent results for PWM I think, but generally you’ll see a voltage between VCC (Vbat in this case I think) and zero. So like 0.5v or 1.0v or something would potentially indicate PWM.

We aren’t just looking for PWM though. It’s much easier to do a quick test of all the voltages than guesstimate where all the traces go (under components and stuff), we want to know the location of GND and VCC on those chips as well.

I’m assuming that we are dealing with a dedicated boost controller which accepts PWM input, I could be wrong. Instead we could be dealing with something more hacky. Once you take another look at the unmarked chip we’ll come back to that.

28

Is that a FET on the non-inductor side? Can't he just bridge the 4.xx volts to its gate directly?

29

This is a boost driver… so no. If it’s not the output voltage then hooking it up to Gate will stop the boost circuit. If it is the output voltage then… well that’s even more Doctor Seuss.

30

I knew that. I was just testing you. You passed. I think.

Was hoping that if it was a bad idea (like it apparently is), it might trigger an idea on a different approach. Please resume your regular programming.

31

Ok, sorry. I had made two mistakes again due to rushing the readings first time, not a great day for me in terms of reliability… Firstly I don’t think I actually gave off ‘clockwise’ readings, but read it from top left then bottom left, below are genuine clockwise readings. Secondly, the unmarked component needed a bit more pressure on some of the legs to show readings, so I have a couple of extra non-zeros. Below are the ‘real’ results (assuming I haven’t made anymore mistakes).

Battery contact side

1.4, 1.4, 4.9, 0, 0, 1.4

Inductor side (inductor to right)

0.1, 0, 0, 0, 4.9, 4.9

Led voltage reads as 1.24v, which surely cannot be right for an XP-G. But my DMM does give reliable readings otherwise, maybe the PWM is throwing it off a bit.

Some more interesting readings from the inductor side component bridged to the LED negative output from the driver are shown below. I’m not sure if they’ll help, but they seemed interesting to me. The 0.1V deficit of the first pin compared to the next 3 matches the 0.1v reading it gives bridged to negative driver input, and the 1.25s match the readings from the LED, I don’t know what that means though.

2.6, 2.7, 2.7, 2.7, 1.25, 1.25