D.I.Y. Illuminated Tailcap - gChart Editions

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gchart
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Bill of Materials for Booster Tail v1.3, v1.4, and v1.5

  • Step-Up Regulator: TPS610995 (YFF pkg for v1.3, DRV pkg for v1.4 & v1.5)
  • Inductor: 0603 2.2uH ~750mA (such as LQM18PN2R2MFRL)
  • Capacitors: 2 of 0603 10uF 6.3V X5R or X7R (such as CL10B106MQ8NRNC)
Schoki
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Thumbs Up Nice

And how about a linear/buck tail for multicell lights?

gchart
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A linear should be pretty easy. And I think a buck would be similar to the Booster Tails, just with a buck IC. Not a bad idea; though my only buck light is a stock L2 that I haven’t got around to modding yet. I could try throwing one together if there’s a demand for it.

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Yes, linear should be fairly easy, you just need to find one with a small package and low parasitic current. It was just an idea to get another model for the “gchart edition” tailcaps. I just had the idea.
(maybe with a small potentiometer to change the current flowing to the tail LEDs? Big Smile )
It’s totally up to you if you want to do this.

DavidEF
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Schoki wrote:
Yes, linear should be fairly easy, you just need to find one with a small package and low parasitic current. It was just an idea to get another model for the “gchart edition” tailcaps. I just had the idea.
(maybe with a small potentiometer to change the current flowing to the tail LEDs? Big Smile )
It’s totally up to you if you want to do this.

A “linear” lighted tail-cap is simple. All you need is a bleeder resistor on the main driver (sometimes Wink ) and maybe a little circuitry on the tail PCB to “regulate” power to the tail-cap LED. In fact, we already have a few designs around here, that have been tested and work really well. Even one design went into a BLF special light, and is now sold separately on BangGood. Potentiometers have already been used, as well as tiny DIP switches, on some designs as well.

What I’m saying is that while he could make a gchart edition “linear” lighted tail-cap, there wouldn’t be much (anything?) new he could bring to the world by doing so.

The Cycle of Goodness: “No one prospers without rendering benefit to others”
- The YKK Philosophy

gchart
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DavidEF, the common illuminated tailcaps (such as those going into the BLF X6) used a simple resistor (or potentiometer) to control the current. While the change is small, the current (and therefore the brightness) will decrease as the cell depletes and the voltage drops. Using an LDO in this case will provide a consistent voltage and therefore consistent brightness throughout the useable range of a Li-Ion cell.

With a traditional illuminated tailcap using just a resistor and LED, assuming a LED vF of 2.5V and a 15000 Ohm resistor…

  • At 4.2V, current would be 0.11 mA
  • At 3.5V, current would be 0.07 mA
  • At 2.8V, current would be 0.02 mA

If you used an LDO that regulated voltage to 2.8V and then used a 3000 Ohm resistor, you’d get a consistent 0.1 mA draw across the entire range of 4.2V – 2.8V

hopefully I did the maths right… I’m not an EE guy

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Ok. I may have mis-remembered then. I thought we had “regulated” tail-cap lights already. Honestly, I haven’t looked recently.

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gchart
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You’re correct! I just found that Lexel indeed tested a version with a voltage regulator back in February (link). It looks like a few people expressed interest, but then all went quiet.

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I just bumped his thread to see if it might take off again, or at least he may tell what the hold up is. Innocent

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I’ve whipped up a few more of these lately.

A while ago I did a Sofirn SF14 in green. BTW, a 14×8mm switch cover fits without any modifications.

And then about two weeks I assembled a Lumintop Tool AA (purple) for the wife using pink LEDs. The stock switch cover seems to be 12×5.5mm which I couldn’t find in transparent silicone. I ended up buying these 14×6mm ones and reamed out the hole a bit.

Last night I put one in my new Ultratac A1, using ice blue this time. The switch cover was the same as on the Tool AA, so I had to ream it out as well.

And I noticed the A1 had a nice switchboard, but someone made an embarrassing mistake… Facepalm

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That LUMINTOP Tool AA looks nice! I think my wife would like one of those too. Where can the purple version be bought?

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I bought it from Banggood (using a coupon from Martin) less than two months ago, but sadly they appear to be out of stock now.

It looks like the official Lumintop store? on AliExpress has them for $19.19, but will supposedly drop to $17.75 in 5 days. That’s about what I paid for mine.

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Really great to see you have solved the problem gchart. I ordered some 1.4 boards and parts.

Life got in the way and I finally attempted a v1.0 just today.  Used 130K resister and just one LED channel.  Worked great on the bench.  Seemed to work fine in a Tank007 with a 14500.  With a Nimh, the taillights would stay lit for a few seconds and then turn off.  The driver seemed to work fine in both cases.  I didn't try any workarounds as your low-current booster solution sounds like the best way to go.

Your lights above look great!

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Thanks! I’ve been really pleased with the v1.4 boards and how the lights have turned out.

The only strange thing I’ve encountered lately is that mode switching with the Ultratac A1 has issues on NiMH: if the tap isn’t ultra-fast, the light flashes the higher mode and then kicks back to low. My theory is that LVP is recognizing the boosted voltage as a Li-Ion for an instant, then sees the voltage drop down and kicks it back to low. Just a guess. Works perfectly on Li-Ion though (which kinda defeats the purpose of a boost circuit, of course).

As you’ve found out with the Tank007, it seems like each of these dual-voltage drivers have their own nuances. So far, both the Sofirn SF14 and Tool AA have worked great.

I haven’t seen the behavior you’ve described. When that happens, does the main LED illuminate dimly?
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^

Not that I can see.  I suspect that, on NiMh, the driver is not leaking enough current to run the tail circuit.  I bet a bleeder resistor would fix the issue. I might try that since it looks like the v1.0 might work in this light.

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I’ve got a new tailcap design with consistent brightness and LVP with minimal additional components. Brief post and video demo about it here, I’ll do a write-up shortly.

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you are genius Gabe.

I finally managed to solder the parts for V1.4 from scratch and it work Smile

Nico -.-

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Nicolicous wrote:
you are genius Gabe.

I finally managed to solder the parts for V1.4 from scratch and it work Smile


That’s great, Nick! Did you use reflow for the boost side, or an iron? I would imagine it’d be extremely difficult with an iron on that WSON package. Using solder paste and a hotplate (or even a skillet) is pretty do-able.
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Low-Voltage Protection, Constant Brightness

This board uses a Voltage Reset Monitor to provide LVP and an LDO to provide a constant voltage (an in effect, constant current). Everything is on a single side for quick & easy reflow soldering. It’s dual-channel, but includes a Bridge pad for making it single-channel.

LVP: MAX809SQ293D1T1G, a 2.93V active-low Voltage Reset Monitor with 0.5uA quiescent current
LDO: NCP553SQ30T1G, a 3V “NoCap” LDO with a 2.8uA quiescent current (typical)

So altogether, there should be a total quiescent current of around 3.3uA while the tailcap is lit, going down to 0.5uA after LVP trips. In comparison to the current for the LEDs (typically 0.15mA = 150uA or higher, this is absolutely minimal)

Standard (16mm): Oshpark

.

Big Switch (19mm): Oshpark

.

Testing video:

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Such exciting stuff going on here.  I have all the stuff to build you latest design (before the above), but big lights have been winning out on my attention for some time now.  Looking forward to building some of your awesome tail lights eventually.  Thank you for sharing your designs and expertise with us. Smile

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Wow. We are in the age of Constant Current lighted tail caps with boost circuit and LVP. Who woulda thought we’d ever be here? Shocked

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gchart wrote:
Nicolicous wrote:
you are genius Gabe.

I finally managed to solder the parts for V1.4 from scratch and it work Smile


That’s great, Nick! Did you use reflow for the boost side, or an iron? I would imagine it’d be extremely difficult with an iron on that WSON package. Using solder paste and a hotplate (or even a skillet) is pretty do-able.

Hey Gabe

i reflow with solder paste Smile

With iron it’s impossible to do Shocked . I tried couple of ways but it’s way too small the legs end up short circuit so i gave up.

Now im in love with AA flashlights Crown

thumbs up to you

Nico -.-

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DavidEF wrote:
That LUMINTOP Tool AA looks nice! I think my wife would like one of those too. Where can the purple version be bought?

BTW, I just noticed that they’re back in stock in the Lumintop AE store for $17.51 with free ePacket
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Thanks gchart!

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I had a bit o’ fun tonight with a new tailcap: my first “smart” tailcap. It’s definitely not a new idea, PD68 was toying with this 3 years ago!

It’s using an ATtiny416 for the smarts side of things, driving 8 individual channels. To keep the power low, it checks the voltage, sets the LEDs, then goes to sleep. For testing, I have it waking up once per second. In a light, I’ll probably have it wake up once an hour or so. Just because there’s an abundance of flash for this use (4K), I added a basic startup animation: spinning circle, looped 3 times. Even with that, it compiles at only like 700 bytes or so.

I could probably do a little adjusting to the voltage on-off levels, but not bad for my first test. By some miracle, this was the first time I ever flashed the 416, and my first time writing code for it. It all came together pretty well.

Here’s the boards on OshPark. This is a small update from what is shown in the video. I’m using a P-FET for reverse polarity protection. I realized that I had two of the legs swapped on my initial design, so I just bypassed the FET pads for testing. This v1.1 has that corrected. Also not that I have not tested this in a complete light – that might detract from the functionality. I’ll update this when I complete that test. Ok, the first in-flashlight test is complete; see post 95.

Edit: BOM

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Wow keeeewwww

Can u post the parts to built Smile

Nico -.-

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I like. It’s fun to think I have a sort of legacy here.

My Favorite Modded Lights: X6R, S8 , X2R , M6, SP03

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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gchart wrote:
I had a bit o’ fun tonight with a new tailcap: my first “smart” tailcap. It’s definitely not a new idea, PD68 was toying with this 3 years ago!

It’s using an ATtiny416 for the smarts side of things, driving 8 individual channels. To keep the power low, it checks the voltage, sets the LEDs, then goes to sleep. For testing, I have it waking up once per second. In a light, I’ll probably have it wake up once an hour or so. Just because there’s an abundance of flash for this use (4K), I added a basic startup animation: spinning circle, looped 3 times. Even with that, it compiles at only like 700 bytes or so.

I could probably do a little adjusting to the voltage on-off levels, but not bad for my first test. By some miracle, this was the first time I ever flashed the 416, and my first time writing code for it. It all came together pretty well.

Here’s the boards on OshPark. This is a small update from what is shown in the video. I’m using a P-FET for reverse polarity protection. I realized that I had two of the legs swapped on my initial design, so I just bypassed the FET pads for testing. This v1.1 has that corrected.


the question would be if its running on a bleeder or needs some intelligent driver that connects battery+ with a FET when off
bleeder and MCU running might get even with 470Ohm too much drop to get a real voltage reading, or even power up as voltage drops

I had same problem with my comparator tail cap and too high current draws in the >1mA range, rund fine on PSU but with bleeder you got no real voltage reading as too high drop on bleeder

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pilotdog68 wrote:
I like. It’s fun to think I have a sort of legacy here.

Great to see you on, PD!

Oh, and BOM added to the post

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Lexel wrote:
the question would be if its running on a bleeder or needs some intelligent driver that connects battery+ with a FET when off
bleeder and MCU running might get even with 470Ohm too much drop to get a real voltage reading, or even power up as voltage drops

Thats a great question. My plan is to have it running on a bleeder, but I have not tested that yet (so keep that in mind before ordering parts, if someone is so inclined). I might have to make tweaks based on how it acts behind a bleeder.

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