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

It is possible, but you may need to replace cell when it is empty. Rechargable battery avoid the need for this. I also have pcb order for this to finish my s2+ flashlight, hope it work out since schizobovine had a few problem with the battery…

Do you think a super capacitor could run the fet for very long?

It could be recharged quickly and most of the time my small convoys are on less than 10 minutes continuously anyway.

I wouldn’t write it off, I’ve got a project I’m in the midst of right now running the entire driver at the tail of the light off a capacitor bank charged up through the bleed resistor(s).
If I can run an entire driver off caps I would think someone could run just a FET, and just full-on/off in the same manor.

50ohms of resistance at the head (needs to be rated 1w or using a bank of 1/4 or even 1/10 Watters) and ~350uF at the tail has been working on the breadboard without issue. Time will tell when I switch to a real PCB with smaller package caps but folomov did it so I’m betting I can too.

I bring this up here cause like I said, I don’t think it should be impossible or even difficult at all to run the switch FET without a battery, just need to do a lil backyard EE’ing.

Oh also lumintop does it in the Ti Tool AAA (but their implementation isn’t all that great TBH)

I slept way too late yesterday after doing tons of work, so sorry if I sounded tired.

Come to think of it, couldn’t we just use a small super cap instead of a lithium-ion battery?

In this small size, and a lower value bleed resistor, it should work very well actually.

Ah! Found the battery from a Canadian supplier:
~~https://www.e-sonic.com/product-detail/seiko-inst-battery/ms412fefl26e.html~~

Nice :slight_smile:

Scratch that. You literally need to order 100$ worth of stuff to get it actually shipped to you.

Again found a replacement :slight_smile:
https://www.mouser.ca/ProductDetail/Seiko-Instruments-Micro-Energy/XH414HG-IV01E?qs=vrQyzjTsotmXvC7BtxG71Q%3D%3D

So, I’ve finally decided to make about 10 of these FET switches.

I’ve finally understood of how this works, but one thing is still unclear to me:
Is it possible to use a super capacitor with a very high value resistor to prevent overcharging to the cap?

It’s the only component that I’m unsure if I should actually order.

Super caps are usually too big to fit tail switch assembly!

This one is the exact same size as the battery lonoceans linked though, which is very nice :D:
https://www.mouser.ca/ProductDetail/Seiko-Instruments-Micro-Energy/XH414HG-IV01E?qs=vrQyzjTsotmXvC7BtxG71Q%3D%3D

And it can actually be shipped to any country, unlike a lithium-ion cell :slight_smile:

It looks like the capacitor is rated for 0.3 volts more than the battery and 50X the charge rate as well. It should be fine the way it is

The stored energy will be about 6% of the battery, might want to bump up the charging rate.

Is there a schematic somewhere? It would be nice to charge the capacitor to the full 3.3 volts if it doesn’t cause other problems.

Yes there is:
https://www.mouser.ca/datasheet/2/360/seiko_XH414HG-IV01E-1202874.pdf

According to post 24 it is being charged to 3.3 volts and the charging is limited with a 2.2k resistor in series with a diode, looks like changing
the charging rate is pretty easy.

The spec sheet for the battery says it has “continued stable capacity characteristics even after the battery is overdischarged down to 0.0V. ”
So maybe its possible to drain the battery to keep it from shorting out and destroying itself while its being installed.

Ok then.

I’ll be ordering the PCBs first, then the components.

Which PCB is the best, or rather, the most appropriate?

I’m quite bad around PCB design, so I don’t know if the Rev B is the most appropriate, or what shiczobovine did.

If your going for the lighted indicator fet switch then rev.B has a lot lower quiescent current. I think loneoceans also added a second fet pad in the middle of the spring in rev.B. Are you building fet switch with the indicator or just the fet switch?

Just the FET switch. I like lighted tailswitches, but I don’t want to do additional work.

I just want to build 2 FET switches for me, and sell the remaining 10 to people who can’t, or don’t want to build these amazing switches.

So, would the Rev B be the best bet?

I’m ready to order the PCBs, but not the components yet.

I’m probably going to sell the rest with my dual BeCu springs so other people can enjoy it.

If shiczobovine’s design uses the same components, I would just order both, 3 of each and wait to see which one works better. Then order more of the design you like. Seems like people are having problems getting the battery installed and your going for the super capacitor. Seems experimental.

Oh now I’ve noticed there’s a place for a linear regulator on the board…

Silly me thought the cell/supercap was directly connected to the battery supply. Now the wait begins since I’ve placed an ordered for 12x boards.

I’m going to order some of these in a few days. I was hoping the bugs might get worked out before I did.
Which boards did you go with blue?

I’m going to order 12 of Rev B, since I prefer the LFPAK33 footprint.

Still haven’t confirmed the payment though.

Do you think I should order 6 of each just to be safe?

Do you think I should go for the 1Oz option, or thicker 2Oz copper option?

Sorry. It’s my 2nd time ordering a PCB.

You can use either one. He describes it back in his first post under the 16mm oshpark link. It’s also in the descripition at oshpark.
If you are using the LFPAK33 that is. :smiley:

Oh no problem then.

Will order the boards right away. Was confused with the Q2 option in the Rev B and the Q1 option in the Rev S, but they are of the same footprint :slight_smile:

Nice, thank you again!