GFS16 - Battery Indicator Tailcap Light & 1mR FET Tailswitch! (Rev B)

Yeah I know, I just rob the switch.
If I want to drop one in something else like a V11R for a lighted switch, I just drop it in. Takes care of both needs. :+1:

I’ll buy another one.
Two by two they marched.
I ordered a couple boards from OSH park but I can’t see myself being able to solder such small components. I was ordering the 17mm high-amp switch pcb by Pilotdog68 (great name) so why not add a few more. Would a stencil be an option for the GFS16? The attachment battery/super capacitor would still be a hurdle though.

Yes, but since it’s more complicated compared to an LED MCPCB, making a DIY stencil will very hard.

I’ll have to solder these components by hand, which I’ve already had practice off, so shouldn’t be hard at all, unlike the boost driver.

After waiting long time for all component to arrive, I finally start building Gfs16 switch to add to my Gxb172 driver. I use Oshpark to order pcb, and I order 0.8mm thick pcb so it will fit in switch. If it is too thin, easier to add some tape to make thicker. First I solder the mosfet pcb.

The battery fresh from order measures at 2.5V. I am using white omten1288 switch. To make switch, first I use hot air and solder the lfpak33 mosfet on the opposite side of the pcb, and then I solder the smaller component on the top. All this is good and easy to solder after practising from Gxb172. Next to make sure I do not short battery, I tape my tweezer in tape. Then, I flatten the lead on the battery and straighten it, and cut using sharp cutter.

This is result. A little bit of balance and soldering is actually quite easy. I measure circuit after to make sure no shorts on soldering. Then finally I solder on white switch.

For the led board, I decide to use white led as light, and red led as low battery indicator. I experiment with resistor and decide to use 27k for white, and 7.5k for red led. I begin with side with small component. This is where I make my first mistake! I only order 2 N-fet, which is a big mistake, because I move too fast and knock the two tiny fet off the table!!

I almost give up but after 20min search, I finally manage to find them. So I advise everyone to buy more component then they need!

Soldering is not too difficult, except for 3 tiny mosfet. I recommend soldering slightly to the side. Then hot air and flux to reflow easily.

This is complete led side. I use 0603 red and white led from Aliexpress shop. I do quick test and it lights up! However I run out of time and will continue later.

Today I complete my Gfs16 mosfet tail switch and led tail light with battery low indicator!! Here is the result. After soldering both pcb, first I test the led board.

I use warm white led for nice glow effect. Since this is good, I solder both board together, + to + and - to -. Then I understand why loneoceans make oval cutout on pcb, since the battery need to stand up and fit through. This was perfect fit!!

I use thick copper spring from noctigon and I use lfpak33 mosfet in the middle. Finally I test low battery indicator with power supply and it work very well, turning red when battery is low, and turn off below 3V. very happy.

When I first measure battery, it is at 2.5V. Then once I finish the Gfs16, I connect it to 4V powersupply and let it charge battery for half day, and the battery voltage is now about 3.0V and going up. Because it look like it is charging through 2.2k resistor, it will take a while to charge full.

Next, I realize I make big mistake.

The Convoy S2+ is not all the same! Sad that my gray S2+ is actually using black rubber boot and not working with stainless steel switch!! So other people trying, you need to be careful! Lucky that I bought clear rubber boot in the past so I use that instead.

Before I install into tailswitch, I make some measurement.

Resistance Measuremenet

  • Original convoy switch - 47.2milliOhm (lowest measurement, click a few times get very different result..)
  • Original convoy switch with wire bypass 22 awg - 15.2milliOhm
  • Gfs16 mosfet switch with battery at 3.0V - 6.4milliOhm

This measurement include the spring. I use power supply to generate 5A constanct current and measurement taken using multimeter for voltage, to find actual resistance.

My tiny battery for above experiment is 3V, maybe waiting a bit longer will be 3.3V, which drive gate of mosfet in tailswitch, so maybe in the future performance is even better. This result is good enough that I do not use bypass spring.

Last I adjust Gxb172 and add bypass resistor of 220 ohm using 0805 resistor solder on the jumper pad (ground side) and the center spring.

Finally my entire Gxb172 flashlight is COMPLETE!

Review for gfs16:

This project is easier to solder together than Gxb172. The hardest one is soldering the tiny mosfets on the led board. The rest is easier than Gxb172. I am not sure why schizobovine have problem with battery, since mine work first time.

Same as Gxb172, I recommend to use magnification to solder with smaller solder tip, thin solder wire. I only use hot air for the lfpak33 mosfet.

Before assemble, I suggest to make sure lfpak33 have no short, battery have no short, and led light system voltage working with power supply. For me I use oshpark 0.8mm pcb for both and they fit Convoy S2+ good.

I recommend the hobby maker to order more tiny mosfets before you blow them on the floor, and I recommend making sure you buy the correct Convoy s2+ light to make sure it fit the stainless steel switch! Make sure you handle tiny battery carefully! Also I use very thin wire (awg30?) to solder + and - pad together. I make sure I keep the switch screw tight, but not overtight to prevent pcb from breaking because it is not as strong as aluminum washer.

Difficulty - 6/10

Cost - 5/10

Result - 9/10! Very nice! I remove one point so it is not perfect so loneoceans can motivate to improve it

I recommend loneoceans add more led on the tail to make ring of light, but I understand how it may have no space since need two bank of leds, and any smaller is harder to solder.

Big thank and appreciation to loneoceans for this cool project and for everyone here who also make their own and inspire me to build this successful project!!

Is it too late to get on the list for a switch?

No, not at all.

There’s one left.

Actually, in my experience the result is much better with a clear rubber boot. The stainless switch requires 3-4x as much light/power and still barely shows through the tiny gasket. It’s not worth it.

Please put me down for 1 blueswordm.

If still available I would like to purchase one.

Great work. I ordered the GFS16 boards with the hope I can solder such small pieces. If I fail, at least I got BlueSwordM giving it a go. I want it mainly for the reliable power capabilities. Not so much for lights. Has anyone tested the upper limit of these? Total novice here but wouldn’t that mosfet get fairly hot. Especially in the context of its vicinity to the switch. Maybe not such a concern, since you could only run a 50 watt led for so long.

I think the limit for reliability is 30A.

At a Vgs of 3-4,5V, the max resistance if 3,00mOhms.

That means, at 0,003Ohms of internal resistance and a driving current of 30A, that would mean power dissipation would be around 2,7W.

For the MOSFET, that should not be an issue if it is soldered down well. No light has reached that power consumption yet for continuous operation.

Very nice job clientequator, a big :+1: from me.
It looks like hot air may do the trick. I’m just glad loneoceans didn’t use another DSBGA4 Digital Temp IC if you know what I mean. :stuck_out_tongue:
I’m still waiting on Oshpark. Hopefully I’ll have the boards in a day or two.
Thanks for the resistance measurements. This should help out the GXB172 alot.
I’m really impressed with the low resistance.
Thanks for sharing and very well documented clientequator. :slight_smile:

I’d like to give a big thanks to Loneoceans also for sharing his creations with the members of BLF. :+1: :wink:

Thank you! Yes this project much easier to solder than Gxb172. if you can do Gxb172, this is no problem.

After using this lighted switch at night and discuss with moderator007, I agree that the design I build is too BRIGHT at night! For the white led on tailcap loneoceans recommend 30k resistor, but this is because he is useing stainless steel switch which has thin gap for light to go through. moderator007 recommend using 100k resistor instead when using clear rubber cap like what I use. Maybe I will adjust it next time!

So, I’ve received my GFS16 PCBs. I now just have to wait for the Omten 1288 switches to come by.

Now, a question.

Where do I actually put the super cap/battery on the PCB that one of the members actually modified?

I would assume it goes where the battery goes (B1, top right pic) but I’m no expert here.
My boards still haven’t made it yet. If you get the super cap working, please post up your results. It might save me some headache.

Oh yeah, forgot to say the problematic PCB is on the left.

Schizobovine used this battery retainer. https://www.digikey.com/product-detail/en/mpd-memory-protection-devices/BK-414-TR/BK-414-CT-ND/2079911
So my guess is that’s it dead in the middle, battery to the round circle and the two rectangles hold the retainer and the switch goes on top of that I guess.
Center circle should be negative and the retainer positive.

Oh, then the build is easier than I thought. I did actually know that the cell was in the center, but wondered how it would get retained.

So, here are the bill of components:

0,70$US each for the boards.
2,33$US for the supercap. Still cheaper than the lithium ion battery, and much safer to solder.
0,38$US for the LDO.
0,24$US for the SMD cap.
0,06$US for the resistors
0,45$US for the schotky diode
0,87$US for the FET
0,40$US for the Omten switch
0,40$US for a single BeCu spring, and 0,80$US for a dual spring

So, if everything goes well, the FET switch should cost, with labor, about 7,00$US.

:+1: