Mod: Fandyfire K2 (with focus on DrJones driver circuits made for electronic switches)

Flashlight Modding and DIY Parts
1

The light:

Fandyfire K2. Its the Solarstorm K2`s twin brother.


Introduction:

Since I first saw the Fandyfire K2, I liked it a lot. I heard Relic38 picked one up, so decided to wait for his review. The light hard some shortcomings, but nothing significant that could not be fixed with some work.

I made a fairly large post in the review thread about how to get the driver out various pictures, ramblings and impressions. The post you are reading now is another one.. :p

Normally I don't make a thread about all my various lights that I just do driver/emitter swaps and and such in. But there seemed to be some interested in this mod, so Ill go a bit in-depth since these electronic switch drivers are not as straight forward as other driver swaps, but they are quite easy if you follow the simple instructions.

I already have a lumodrv in a Small Sun ZY-T29 and a in a Small Sun ZY-T11. Two lights I like a lot! :)

They are wired like this: (pictures from DrJones site)

Its even possible to connect the contact board with switch by only using 3 wires (if you are able to get one side of the switch signal and battery negative signal in the same wire. Ill be using four wires on my K2 board, because im a noob, and its simpler to wire when you are a noob. :)

I love those lights, which are due to the great UI of the lumodrv! Stock UI on those lights suck!

When looking at the overview of DrJones driver circuits his drivers might seem quite complicated, and they do require a bit of time in order to be fully understood and set up as nicely as possible to your preferences. But what do you expect when you can do a bunch of things from a single switch? Once you learn the UI they are quite lovely and easy to use! They make great toys for a flashoholic.

Im not sure when he released the "Q" variant of the mobydrv. The mobydrv is nicely programmed for cycling. The "Q"-edition uses quicker off cycle and have more brightness steps. Thereby better suited for normal flashlight use compared to the standard mobydrv. I wanted to try one out, and it have been waiting for a host for some time.

Fandyfire K2 will be my host for the mobydrv/Q variant. :)

Testing the driver circuit:

I replaced the stock wires on the mobydrv with 22 AWG silicone wires. The K2 head is quite deep, and its nice beeing able to use a lot of heat without worrying about melting the wires. And I have future plans for even higher current...

I tested the driver with a bare switch first (not from K2). The electronic switch is attached to the negative (outer ring) and the 4. star from the left. Otherwise, its just as any other normal driver of this type. Make sure the wire that is connected to the 4th star does not connect to anything else than the star. You could also use one of the legs on the programmable chip (see picture in introduction made by DrJones). But I prefer to use the star. Using large wires is not important. Its only for a signal, not high current or anything.

This gives you a picture of how it works inside a flashlight. There is no need for a mechanical switch. The driver circuit always gets its power and can be turned on and off with the electronic switch.

Installing the driver circuit:

I removed all components from the K2 driver circuit. It will only be used as a contact board, and switch holder. I attached some wires to the switch. Color or which wire who goes where does not matter, as long as they are connected to the right places you are good. (4th star from left for one of them, and outer negative ring for the other).

Then I found a place on the bare K2 driver circuit board that was connected to where the positive side of the battery touches the board. I used the beep/ connection finder/ohm setting whatever it is named on the DMM to find this place. (Please excuse my sophisticated language/explaining skills and superb electronic skills :p )

I also put some kapton tape on the K2 board, just in case the boards should be able to make a short circuit (I doubt it, but better safe than sorry).

Same with the negative..

Just testing the switch from the K2 board again..

Put the driver circuit back into the flashlight... Even better! :) 2,84A

These 350 regulators tend to over perform just slightly based on my experience. (8*350mA= 2,8A)

Success! :party:

Other:

The sloppy stock O-ring on the body was replaced. My brother have hundreds of O-rings so I went to him. But he did not have the perfect size for this light. I ended up using one that is a bit too small, so I doubt it be water proof. But it should be marginally better than no O-ring, or the annoying stock over-sized O-ring.

Future plans:

I just wanted to test this driver circuit. Ill get back to my impression once I have played more with it.

I will add more 7135s. Probably 3(3,85A total), if not 4 (4,2A total). That should be the absolute upper limit. The beauty of these Drjones drivers are that if you don't want the full 100% output you can just program high to be slightly lower.

When I do an emitter swap. Ill be using copper mcpcb (and XM-L2), which is default for most of my lights. Ill report back if there should be any mechanical issues, but I doubt it. I will be using a Sinkpad since that is slightly taller than Noctigon, and thereby closer to the height of the stock aluminium MCPCB.

Reserved for feedback on the lumodrv vs mobydrv:

....

Until more ramblings, lumodrv is my preferred choice. But both drivers are awesome in their own way and for a certain type of use.


Almost last words:

I don't normally do this much testing, or measurements. But its always nice to test the driver before putting it into a light. The pictures should also make it easier to understand.

As for any additional heatsinking to the mobydrv, im not so sure it needs it. I have not noticed any issues with these drivers hanging fairly loose in my other lights. If your light is seeing lots of rough use, then potting the driver circuit to the contact board might be an idea.

The K2 driver circuit board is also very loose now. My board was not proper press fit, meaning without any silicone holding it in place it is loose. Ill probably end up using a small dab of fujick when when putting in more permanently.

Epilogue:

Reserved...

The stock light was decent. Now, this light is pretty sweet (except the tint). Upping the juice more and putting in a nicer emitter should turn it into a very lovely light! :)

Ill sit back and fine tune play with the programming now... :)

Oh, last but not least. This light was my gift/price from the Old Lumens build from scratch contest. Thank you Old-Lumens, Lightscastle.com and last but not least, Drjones himself for making these great drivers ! :)

2

that was some nice mods :slight_smile:
i wonder if work with this light too

3

Thanks,

I don't see a reason why it should not work. Unless there is close to zero space in the driver compartment.

Even the small Small Sun lights I mentioned in OP has space for a Drjones driver.

4

my TF A9-2 still on its way and planning to use Qlite driver.
i want a 4 modes : 5mA - 2% - 25% - 100% on it so i need to solder the cable switch at 4th star isn’t?
all this time what i do is only swapping Led and Driver only :slight_smile:

5

A Qlite driver does not work with electronic switches. Qlites and all normal Nanjg 105C style drivers needs to be used with a mechanical switch.

DrJones program his drivers so that they can be used with electronic switches.

Edit: If you want to use the Qlite in the TF A9-2, you could possibly rebuild it with a mechanical switch, but that would require some mechanical work along with more space in the driver compartment. This is why the custom programmed Drjones drivers come in handy. They offer features that goes nicely together with an electronic switch.

6

Great! I love the DrJones drivers. Between the DrJones driver and the Taskled drivers, there's some sweet program options for making really nice lights.

7

is that so?
thanks for the info :bigsmile:
when its arrive i will strip it up

8

Thank you for doing this write up and providing me with a road map for my first mod that uses an electronic switch.

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Thanks RaceR86. Pictures for a wally like me make things a lot easier.

10

Got mine modded with a XM-L2 U2 1A/Noctigon reflowed on a 22 gauge 7/8" copper disc, added 3 R075 resistors, and am getting 3.4A at the tail from a MNKE IMR 26650 at 4.18v.

Problem is I'm losing 100 lumens from the stupid tail spring (1,153 lumens @start assembled, 1,258 @start with the tailcap off and battery jumpered) - that's 8.3%. The battery tube on this light is gorgeous, but I just can't get that tailcap off (glued threads?), and the spring looks like it's simply clamped down by threading on the tailcap, pinching it. It's a really long spring too, if it were uncoiled. I'm seriously thinking of tap soldering on a copper wire to the battery neg. end, but at the + end, could be risky to position it to get it clamped...

Ugh -- I hate glue...

11

Tried some jury riggin of solder wick on the neg. end of the battery, but didn't really work - idea was to try to cicumvent the coils of the spring, but probably couldn't get a good contact with the spring wire near the body.

Tried a Powerizer 26650 @4.18v, 3.99A tail, and that did the trick: 1,248 @start, 1,214 @30 secs. Also, removing the battery tube and directly jumpering the Powerizer shows I don't lose much output at all.

Conclusions:

  • the driver doesn't seem to regulate well because low resistance cells get a higher tailcap amps reading, higher lumens output (maybe because of my resistor mods?)
  • weird, but the Powerizer seems to compensate for the resistance of the tailcap spring pretty well. I assume though as the Powerizer drains and loses voltage, droppage is more significant becuase the spring's resistance will kick in
  • Run this light on a Powerizer!! Gotta order more - I have only two
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My K2 arrived friday with a sealed tailcap.Yesterday I put the battery tube and tailcap in a casserole without a bag,in boiling water.About 30 seconds later I unscrewed the tailcap.There's no electronics in there,and yes,the spring is just clamped between the two.There is an o ring as well.

13

Thanx Billy! Hhmm, I should try the boiling water. Some how, I want to copper braid that spring. Is it easy to re-assemble, clamping the spring end?

14

The tailcap is completely anodised,the outermost coil of the spring sits in a recessed ledge in the battery tube.Once freed,the spring should be easy to braid,maybe exploit the"sponginess" of the braid when it's clamped between the tube and cap to further increase contact.The end of the battery tube is bare alu to make contact with the spring.They probably glued the tailcap to avoid contact issues with a less than fully tightened tailcap.My tailcap was only lightly glued.You need to seperate the head from the tube on reassembly,so the spring sits in the recess ,so once the spring is braided,you don't use the tailcap to change cells anymore.

15

I tried 45 secs in boiling water in a bag - no dice. Then tried 3 mins - again no dice, would not budge. Now I'm goin for 5 mins without a bag - in a pot of boiling water. I'm using leather gloves, then went to a rubber jar opener pad with a rubber coated glove for hot pots....

If I get this working, will try same method with the UV-S5 tail - same problem of being well glued.

Update: No, no good. After 5 minutes in direct boiling water, with a leather glove and rubber jar opener pad, I got a great grip on, could apply a lot of pressure, but couldn't budge it. Anyone have any other ideas?

Billy - you had it in boiling water for just 30 secs and it opened by hand immediately after?

16

It looks like you got the eager loctite applier!30 seconds or a minute,I can't guarentee,but definitely not 5 minutes.Mine had less than one turn of the thread treated.I had tried to undo it without heat,but no go,but as I knew it was threadlocked,I didn't persist.When I took it out of the boiling water,I thought it would probably need longer,but it released first time with just a tea towel.I think I was Lucky.

I googled undoing loctite and the concensus is heat,maybe 200°f,some say 250°f and even the red permanent should soften.First I'd try longer in boiling water,say 15 mins.If it doesn't give after that, then the soldering iron applied on the edge of the tailcap(with the head seperated from the body)or a lighter,yellow or blue flame,is supposed to work in seconds.A heat gun was another option,but a hairdryer won't do.Somebody mentioned a lube called Inox which disolved the stuff while others said acetone shifted their fasteners,though I tried cleaning some of the residue with it,I can only say...underwhelmed.Sounds like pinpoint heat in escalating temp is the way to go.Good luck and persistance.

17

Nice to hear that you liked the K2 Tom.. (Saw you recommended it in some other threads some time back when I was reading the forum from my cellphone).

I never updated OP. But I added more 7135 regulators to the driver and came across the same issue. Lots of resistance in the rear tailcap spring. Making the amp readings lower than they should be. Im not happy with compensating by using low resistance cells so I got rid of the light in OP about 2 months ago.. (to someone who did not need 4A++ out of it..)

Its a nice light, but im getting quite picky on such details, and there are many other lights out there.. Using a low resistance cell with lower capacity, is not an ideal fix IMO.