Is an illuminated tailcap possible?...... Solved?

Flashlight Modding and DIY Parts
50

^ Interesting chip there Crux. It sure seems like it could be very useful for all kinds of purposes.

I forgot to share a thought last night when I posted. I'm pretty certain a limiting resistor will be needed in the tail cap. The moment the light is turned off (buy clicking the switch to the open position), the driver will be trying to pull current. The tail cap emitter will be overloaded as it will be the only remaining path for current flow.

Routing a Batt+ wire to the tail cap is not necessary as Antenne has reported. He/she even gave tip on a quick way to check if some positive power is flowing into the flashlight body by saying this:

" . . . So far my tests suggest that it would be best to test the light in question by simply put a LED between BAT and Body with tail cap taken off and see if it lights up. Worst case would be that it burns up "

If a driver has voltage dividers (like for LVP or tempature sensing), it already has some resistors connecting Batt+ to Ground (flashlight body). So, when the switch is off, the light body actually is positive charged. The current from the driver voltage dividers will probably not give pilotdog68 the 2mA she wants, but it will give some of it.

51

What did I say that made you think I was a girl? :~

Anyways, based on what you said I could possibly just swap the LVP resistor for a different value? I would give up my LVP, but I don’t think I’ve ever needed it anyways. I always recharge at the first sign of dimming.

(EDIT: Actually, if I use a different resistor, maybe I could just tweak the LVP values in the FW so it would still work.)

……………………………………

It’s interesting how divided everyone is on this topic.
It seems very logical to me that this would work pretty easily, but others seem to think it’s basically impossible without running a new bat+ wire.

I think the hardest part will be making the tail LED bright enough without having too much current draw.

52

I’m sure as pointed out you could get it to work as is but there are a number of caveats that could make it less than straight forward. Adjusting the voltage divider would mean losing/having to tweak the LVC, I wouldn’t run a light without an LVC just for the sake of having a standby light.

Getting strange mode behaviour/losing memory, stuff like that could also crop up since we’re at least partially powering up the driver board and MCU. I don’t know for sure what the results of that could be, and it would depend heavily on the driver and the firmware combination.

I haven’t tested it but completing a circuit where everything is in series and involves a clicky MCU that’s designed to work with on/off power, there’s potential for some unintended behavior. Right?
If it was a a driver based around a momentary configuration then that at least wouldn’t be a concern.

It just doesn’t seem like a particularly clean solution to me, whereas finding a way to power the led with it’s own connection to battery + would (if at all possible) be a cleaner solution, at least electronically.
I’d gravitate towards that myself since I don’t know enough about electronics to fully visualize the complications of the other method.
Like I said the soup can lights make the batt + approach a no brainer, for anything else it’s going to be a pain.

So it’s cool to see testing done on this anyway, only way to find out what’s possible/feasible :slight_smile:

53

I have no idea why I thought that. My sincerest apology pilogdog68.

I would leave the LVP circuit alone unless you are sure your FW has not LVP code. The LVP has 2 resistors in series from Batt+ to Ground. The MCU connects between the 2 resistors. You would need to decrease the value of the second resistor (One that connects directly to Ground) in order to flow more current to the flashlight body. That would lower the voltage that the MCU reads and step your light down if it has LVP code.

EDIT: I agree with LH that it may cause mode switching or other issues in some drivers. We won't know till we try. I would think with so little current (and most of it being converted to photons) that it may not cause any issues.

EDIT2: I missed the part in your last post about tweaking the FW pilotdog68. That could work, but would probably be a bit of trial and error to get everything working right. Seems much easier to just find a positive spot near the ground ring and reflow a resistor (may need a wire or copper strip to reach)

54

Yes definitely potential for that. Just spitballing here, but maybe tweaking the OTC settings in STAR off-time would correct it enough that mode switch would still work?

I don’t want a wire running down the tube because the Convoy lights are already tight, and it would make battery changes a royal pain. If my idea ends up not working, I’ll just give up on this.

………………………………………….

Lol no worries!

…………………………….

On a single sided driver you could just scrape away a little mask and use the resistor to bridge the gap. A double sided driver could be a little more tricky, but definitely doable.

55

Any ideas of how the Niteye MSC series switch works?

BLF review

56

Here’s an idea based upon the BLF Edition Lumintop SD10. Buy or make a battery carrier with plus and minus on both sides. You get physical reverse polarity protection and can supply power to the tailcap.

57

I also found this - http://www.google.com/patents/US20140091725

Haven't read it though, too legal.

58

RadioShack sells a blinky LED (blinky circuit built in to package). Model: 276-036

I know these draw a spike of current when they blink ON, but it's simple and may just work as drawn in the OP. I'm not sure how this or other circuits behave as the cell voltage drops toward zero. They probably continue to pull current past the lower limit of where you want to keep the cell. :(

I'll see if I can find any in my parts drawers tonight...

59

How much current do you need to make your smd glow and where do you get the voltage potential. Current flows through the case but between driver gnd and battery neg there is very little voltage potential. The lvp resistors drop the same voltage as the main led circuit but only pass a few tenths of a mA. Answer the first part of the question above and recalculate the value of the resistance needed to replace the lvp resistors. Lvp will be disabled since pin 7 needs to see a voltage lower than what you need to power the smd.

edit this is all screwed power to the SMD cannot come from the case. If some power is bled from the lvp circuit it has to travel through a separate wire back to the SMD + resistor and then to the case. It must remain a separate path until the paths are at equal potential.

60

On my way home from work I stopped at one of the remaining radio shacks and grabbed some leds and resistors. I got 3 red 5mm leds, one 3v, one 1.7v, and one 3v blinking.

I first tested them a p60 light using a single mode AX2002 driver and an XM-L.

I put the 3v led in parallel to the main switch with the positive led lead connecting to the battery tube. I did not use a resistor.

It works perfectly! With the switch open, the led lights up to a nice locator brightness. I measured with my DMM in series with the led and they pull about 0.5 miliamps. The XM-L does not light.

When when the main switch is closed, the secondary led shuts off and the main led works normally.

Next I tried it with a 4-mode solarforce drop-in with an xp-l, and a 4 mode custom dropin with one of wight’s PZL drivers and a Nichia.

With the switch open, the secondary led works as expected, the Nichia lights an almost invisible amount, but the xp-l does not light at all. The secondary led seems brighter with the PZL driver.

With the switch closed, the secondary led goes dark and both main leds come on, but neither changes modes.

So I retested these two the same way, but with a 1kohm resistor in series before the + end of the led. With the switch open they both act the same, but this time the solarforce drop-in functions perfectly, changing modes without a hitch. When I turn on the custom drop-in, it goes into lvp, a few blinks and then off.

………………….

I’ll test with the blinky led next

61

Just tried the PZL/Nichia with the flashing led. Once it’s on, it appears to work great. The issue is that when you first turn it on, it just comes on in a random mode. I think the “flashing” of the led is changing the mode of the driver with each flash while the light is “off”

62

I've seen it often, but I'm still amazed at how a quick experiment can answer so much speculation. I was busy last night any didn't have time to dig into experiments. Kudos to you Pilotdog! As was speculated, the operation of some drivers is affected. I suspect the secondary current keeps the MCU from shutting OFF quickly enough or at all. If that is the case, then putting a resistor (~1k ohm?) from batt+ to batt- right at the driver should bleed the current around the MCU restoring normal operation.

I think you are on to something.

63

i wonder if double throw switch can fix that, one leg driver, other leg small led in the tail.

64

Does anyone know where I can get the clearest tailcap boots?

65

I added a 1kohm resistor between + and - on the PZL driver. The tail led is now a bit brighter than before.

The driver is normally off-time no-memory, always starting on moon.

With the tail led and extra resistor, mode switching works normally, but it appears the driver never actually turns off. This results in essentially “next-mode memory”. I can’t stand that type of memory, so if I can’t get that fixed, I’ll be nixing this idea.

66

I’m glad you found a way to make it work. My negative statements were based on my knowledge of the 105C based drivers but I’d rather be wrong than have someone stop. I’m sure it can be made to work in most lights but might require different methods. You might try different value resistors to see how behavior changes.

67

I wish I had more components to work with. I bought 1k and and 560ohm at radio shack, otherwise I just have the smd resistors needed to build the common drivers.

68

Several things to try. Try the 560 ohm on the PZL (or just add a second 1k). Try a 1k or 560 ohm in series with the tail LED. Or some combination of these.

(How many materials did Edison try to make a filament from?)

Also, what LED are you using in the tail? Vf of the red ones is ~1.8V at low currents while blue and high eff. green are ~2.7V. The higher the voltage drop at the LED, the lower voltage to the PZL (when the switch is OFF). This should help. And the blue (or white) and high eff. green may be brighter than a red to boot.

I don't have that driver or I'd run some tests myself...

69

Currently there’s a 1k on the driver, and a 1k in series with the LED. Most of the results I’m giving are using a red led from radioshack rated 3v, 2.5mcd, 15ma max.

I post in the STAR fw thread asking if there was some other way to make the driver “think” it isn’t powered