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

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

The specific light in question is the DQG clicky AAA. I received one today and the tint, beam and finish of the light are all great. However, the relatively low frequency PWM on the low mode is not..

Possible fixes for the PWM would be to switch it to high mode first, so I could ignore the PWM modes unless I really needed them. The first version was high mode first, but I know that it’s almost certainly impossible to change this mechanically.

The second and more plausible option seems to me to be to remove or bridge a component on the board which produces the PWM dimming. I have little to no experience modifying components on circuit boards themselves (I’ve only added/removed AMC7135s and bridged contacts on NANJG drivers to change modes), so I’m not sure if this would be feasible. Is PWM produced in it’s own component, or within a more general unit which would not be possible to remove without affecting the general function of the circuit?

The three largest components on the back of the PCB are etched with ‘2300’, ‘K24’ and ‘CFC3W’, if that means anything to anyone?

The third option, which may or may not be worth my while, would be to purchase a new driver for it. It looks to be 10.5 or 11mm in diameter, does anyone know of a decent and good value boost circuit in that size?

Edited by: RedForest UK on 07/29/2014 - 15:31
RedForest UK
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Reading around a bit more has led me to believe that the 6-pin CFC3W component is most likely to be the MCU, and that one pin should account for the PWM. So, by bridging this pin to something I may be able to remove the PWM modes.. All very tenuous atm though, does anyone more experienced with electronics have any input?

WarHawk-AVG
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Yes, bridging it might remove the blinkies, but also might remove the modes

Do you have a picture of the driver?

There is also in the works a 10mm driver with custom firmware that should make it into a 3 mode high frequency PWM flashlight
https://oshpark.com/shared_projects/TAoalgqb

Knowing what kind of driver it is and seeing what is tied into what (what pin the MCU goes to the FET or whatever) will give you an idea of which pin is the PWM pin

musicmagic
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at least with the 7135 based drivers, if you bridge the pwm pin, it will be one mode, high only. If you do that, you are essentially removing the MCU from the circuit.

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RedForest UK
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Thanks for the response guys, I realise that removing the PWM will lose all modes as that is the only dimming mechanism on this light. But it would still be worth it for me as I can’t stand low freq PWM anymore.

Here’s a link to some pictures of the circuit: http://imgur.com/a/L3rjP

Sorry it’s a bit messy. I spent an hour or so last night bridging various contacts by trial and error, with effects varying between no light at all, or functioning as normal (as far as I could tell anyway). None removed the PWM without stopping overall light though, so any ideas based on the pictures would be very welcome.

wight
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Aren’t you missing pictures of the other side?

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comfychair
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What's on the other side?

Without knowing that, or being able to poke at it with a meter myself, my first guess would be that you need to remove the 6-pin chip, and add a jumper from B+ to the left-most leg on the 3-pin FET (marked '2300', leg you need to jump to is under the '2').

If there is a current limiting resistor on the other side of the board, that will remain functional, so your single mode current should be the same as the old high mode's current.

wight
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comfychair wrote:

What’s on the other side?

Without knowing that, or being able to poke at it with a meter myself, my first guess would be that you need to remove the 6-pin chip, and add a jumper from B+ to the left-most leg on the 3-pin FET (marked ‘2300’, leg you need to jump to is under the ‘2’).

If there is a current limiting resistor on the other side of the board, that will remain functional, so your single mode current should be the same as the old high mode’s current.

I figure there should be both a boost controller chip and a ‘modes’ chip. Without seeing both sides of the board I just can’t figure what’s what.

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RedForest UK
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Thanks again for your input. I thought I might have to remove the driver to show the other side, but was hoping it may be possible to figure out with minimal disassembly.

Comfychair, please excuse my ignorance, but what would be the ‘B+’? Just the central positive contact?

Also, would bridging all contacts on the 6-pin MCU have the same effect as removing it entirely? I’d find it more fiddly to put it back on than clean up the pins again.

wight
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RedForest UK wrote:
Thanks again for your input. I thought I might have to remove the driver to show the other side, but was hoping it may be possible to figure out with minimal disassembly.

Comfychair, please excuse my ignorance, but what would be the ‘B+’? Just the central positive contact?

Also, would bridging all contacts on the 6-pin MCU have the same effect as removing it entirely? I’d find it more fiddly to put it back on than clean up the pins again.

B+ is battery plus – the positive contact.

“All the pins” certainly includes both B+ and GND, so no… don’t do that. (That would be a dead short for the battery).

Comfychair may not agree with me here, we’ll see, but I really halfway suspect that the SOT23-6 you see on the bottom there is the actual boost controller. I’d take the board out. If there was something preventing me from taking the PCB out I’d hardwire a battery to it, set it on medium, and measure the voltage of every pin on the SOT23-6 against GND. (then post that info here…)

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wight wrote:

Comfychair may not agree with me here, we’ll see, but I really halfway suspect that the SOT23-6 you see on the bottom there is the actual boost controller. I’d take the board out. If there was something preventing me from taking the PCB out I’d hardwire a battery to it, set it on medium, and measure the voltage of every pin on the SOT23-6 against GND. (then post that info here…)

I would agree with to on that.

What light is this? You really need to get to the other side, you’re best chance will be by accessing the MCU, none of those components there are the MCU.

 RIP  SPC Joey Riley, KIA 11/24/14. Now I am become death, the destroyer of worlds.

RedForest UK
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Ok, point taken.

Here’s a link to some new pictures of the back of the board: http://imgur.com/a/qrw97

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.

musicmagic
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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.

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wight
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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.

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RedForest UK
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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.

wight
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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.

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RedForest UK
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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.

musicmagic
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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.

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wight
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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

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

RedForest UK
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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.

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

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RedForest UK
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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?

wight
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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.

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RedForest UK
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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.

wight
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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).

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wight
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RedForest UK wrote:
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.

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.

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ImA4Wheelr
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Is that a FET on the non-inductor side?   Can't he just bridge the 4.xx volts to its gate directly?

wight
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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.

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ImA4Wheelr
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I knew that.  I was just testing you.  You passed.  I think.  Wink

 

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.

RedForest UK
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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

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