D.I.Y. Illuminated tailcap

Hey all, hoping to get some advice. I ordered some of the LEDs djozz linked above and a built a 19mm rev5.1 board with them, but it doesn’t work nearly as well as his does in the video. I first built it using a single 22kohm resistor and it was basically a red flashing board, with the colored emitters just dark the rest of the sequence. So I figured maybe it was a power/voltage issue not allowing certain colors to illuminate, so I lowered my resistor to the same 3.3kohm value djozz said he used above, with the biggest difference being that my board only uses 1 for all 6 emitters; its not the 3-channel board. Now my tail has roughly 3 colors, red > green > blue, with some flashing and pulsing in between (maybe there’s supposed to be other colors in there? it almost looks yellowish sometimes.), but after a cycle or two, just a couple of minutes, the blue and green stop working too and I’m back to a board that pretty much just pulses red. Its really not a bad look, the slowly pulsing, undulating red, but its not what I was expecting. If I use turn on the light, cutting power to the tail, it starts over again with multiple colors, but every time, after just a few minutes of working, its down to just red.

Any thoughts? Should I try even less resistance since all 6 are pulling through the 1 resistor? I don’t really want it brighter, but I may have to. Are these just not as good as his original emitters?

What is the tailcap current right now?

As menrioned in my post above I noticed the influence that leds have on each other too, blue is getting scarce if you let it run for a while. My circuit at least has the 3.3kOhm before 2 of the leds parallel, and that 3 times. My interpretation is that the leds have the most influence on the other led directly parallel and less on the other 4 leds. You can also try a separate resistor before each individual led, that may cause the least influence, or one resistor before all 6leds parallel, in which case they all feel each other. Is that last the case in your build?

Yes right now its just got 1 3.3K resistor with all 6 LEDs in parallel afterwards. But the board does have pads for individual resistors. I’ll try rewiring it with separate resistors to see what effect it has.

My tailcap reads 0.64mA at first “connection”, but it fluctuates between 0.4-0.8 as it runs through its cycles.

Could probably also try a lower resistence (for a single resistor setup), right? djozz is using 3x 3.3K vs 1x 3.3K. I imagine that’d make a big difference.

djozz said he was getting around 1ma. So I agree, I would try a lower resistance to start out with. Plus since things improved with 1ma, it might keep improving with lower resistance.

So my next iteration will be a (6.8 Ohm) resistor before each led and see if that will be interesting or boring. Perhaps I hit the most interesting circuitry by accident.

So I rebuilt it using an individual resistor for each led, plus I lowered the value quite a bit too - 1.1k 1.5k per. I know, you should only change one thing at a time when testing but I didn’t have much time. The result is a tailcap that works as expected, shows all colors for at least the last 10 minutes that’s it’s been going, and is WAAAYY too bright. Now it’s pulling between 2.7 and 3.1 mA. So I’ll probably dial a bit more resistance into it when I get a chance, but this is an improvement for now. Thanks all.

EDIT: And I’ve lost the otc on the driver - no long-pressing and next mode memory. Definitely too much current

Alright, so final update on my tailcap for the time being: First a correction — I’ve got 1.5kohm resistors on each of the 6 LEDs, not 1.1kohm. Sorry. I left those alone. Since the board also has a single parallel resistor that effects all the LEDs, I started adding resistance to that pad and testing. 500 ohms didn’t help, neither did 1kohm. 1.5kohm did the trick though - gained me back proper mode switching and the tail LEDs rotated well, at least for a little while. After a few cycles though, the blue started dropping out again. Not sure why, but it seemed like a bit more current/voltage would be required. I didn’t have a good choice of resistors between 1 and 1.5kohm, so I pulled the head apart and lowered the bleeder from 560ohm to 330. That did the trick. Mode switching and the tailcap work as expected, with the small exception of some occasional random “flickering” in the tail as it changes colors. Tailcap draw fluctuates from 0.85ma to ~1.1ma, so I’d say the 1ma target on these LEDs is about right. Definitely not my most efficient tailcap, but its fun.

Nice empirical research emarkd! It fits well in what generally happens in the lighted tailcap developments: no idea what really happens, nothing is predictable, but we find a way to make it work. :smiley:

Finally got around to adding a “proper” (Gen 2, Rev 5.3 style) tailcap to my Astrolux SS. I just got solder paste yesterday and decided to try that for soldering the LEDs. A little dot on all of the LED pads, placed the LEDs, and put it in a pan on the stove. It worked out wonderfully.

I did 3x blue LEDs and 3x white LEDs, with each channel behind a 20K ohm resistor. Used a 560 ohm bleeder on the Mtn FET+1 driver. Measured draw at 0.1 mA (my DMM only reads to tenths). Looks pretty nice, if I may say so.

In case I haven’t said it yet, thanks PD for putting these boards up on OSH Park. They certainly add a nice touch to my favorite lights.

Looks good!

I found 3.3k resistors give the best colouration and patterns but it’s abit bright for my taste whereas 6.2k resistor is a tad dimmer but it give some interesting patterns too.

I guess each colours depending on the current that drive the LEDs (i.e. Red colour needs high current flow whereas green need high current and blue and other colours are in between). Sorry i don’t have a multimedia to check and these are just base on my observation :smiley:

I guess there is no right or wrong answer and it’s just trial and error to pick whichever patterns / colouration fancy your eyes :slight_smile:

Looks great! Somehow I had completely passed over those 5.3 boards and didn’t realize they were only 2-channel. I’ve found myself wanting that in several lights but all I had were the 5.1 3-channel boards. So 5.3s ordered! Thanks!

Each of mine are seeing about the same resistance - 3k. So for anyone wanting to play with these color-changing emitters I’d say that’s a good resistance to start with. I agree mine’s waayyy too bright so I think I may open mine back up and try to physically filter it somehow. Its already terribly inefficient, might as well go all-in :slight_smile:

Here is another link for those RGB leds from Aliexpress. I searched it out because the ebay seller didnt ship to my country. Hope this is useful for some one.

0805 RGB Slow led @ AliExpress

And it is cheaper too :party: thanks for the link.

@emarkd: I have combined the 3.3 kOhm resistors on the ring with a switch board with pot, so I can adjust the overal brightness (but I like the brightest setting anyway :smiley: )

I would prefer much dimmer and more efficient, but I just can’t get the emitters to function properly at lower current levels. Even at ~3k total resistance, mine still eventually mostly lose blue, but at least they’re not just pulsing red like they were at higher resistance levels.

Speaking of, this tailcap was completely distracting last night when I laid down for bed. The green and blue is so bright I could see it reflected off of the ceiling. So I took it back apart this morning and added a disk of filtering material made out of this stuff, something I had laying around from other more “standard” light-dimming projects around the room. It went from this:

…to this:

…and is now much more like what I wanted. I mean its totally absurd, honestly — I’m running this thing at a full milliamp just for it to function properly, then mechanically filtering it back to a reasonable light level so I can actually stand to use it — but I like it so I’m keeping it :slight_smile: I’ll just have to be careful not to kill cells in it.

This weekend I got around to putting together a tailcap for my S41S (colored version - not my first choice, but when you get it for free… not going to complain).

Used 3x blue and 3x green LEDs on a Rev 5.3 board. Blue LEDs are behind a 20K ohm resistor, and a 39K ohm for the greens (and they’re still bright!). Driver is still the stock BLF A6, but with a 680 ohm bleeder added.

I’m looking for the easiest most efficient rev to add light to convoy s2+ tailcaps. I am using a fet+7135 driver. I think I’m looking for a single color light all controlled by the same pot. The less complex the better because I’m not the best at soldering. Can anyone help me?

The tailcap is pretty simple, the harder part is the bleeder for the driver so the modes work like they should.