The observed performance difference on the power supply was actually caused by the difference in rising edge detect (flashlight turning off, tailcap turning on) versus falling edge detection (tailcap on, battery running down). The spec’ed cutoffs for rising and falling can be seen at the end of this translated datasheet.
Unfortunately a capacitor cannot change the system voltage, it will only mimic the battery voltage. And there’s already a capacitor in place.
In short, the HM1160 is unfortunately a “take it or leave it” scenario. It’s handy, but not flexible. For flexibility, you’d need something like one of my smart tailcaps which is running an MCU and can be programmed with any voltage cutoffs as desired. Or… I’m currently finalizing a tailcap that is similar to LoneOcean’s tailcap (in concept and functionality, not design). It’ll use 4 red/blue bi-color LEDs and a couple low-power voltage reset monitors to switch from blue to red to off at whichever cutoffs are desired (in 0.1v increments). I hope to have it ready in the next few weeks.
Yes, as long as you’re comfortable installing the tailcap and ensuring that your driver has an appropriate bleeder resistor. And with the understanding that the HM1160 provides preset cutoff voltages and those cannot be changed. I ask $3 per assembled board. Domestic shipping for $1. International depends… I’m legally required to use package shipping which is usually $13, but I have snuck these through in standard envelopes (at your own risk) for like $2.
Practically all IC’s like to have capacitors around them to help smooth out any small voltage fluctuations. You could probably get by without, but they’re so cheap, you might as well follow the manufacturer’s recommendations (as is done in this circuit, which is taken right from the datasheet).
I think this one has been asked before. Anyway, I don’t think it’s feasible. The issue is pretty fundamental to the way the tailcaps work.
When a normal, power-interrupting clicky switch is off, the lighted tail is an alternate current path. The full loop is Battery Positive across a bleeder somehow to ground, through the lighted tail, to battery negative.
With the FW3A, there’s no power-interrupting switch. So no gap to bridge with the tail there. Could you make a lighted tailswitch board? Not really that either, because you’d need an additional (a third) current path to the switch to power the LEDs.
I don’t think a smart tailcap is possible for the FW3A without a lot of effort. You need a good constant power source to measure.
The main electric path in the tailcap (from what I can tell, that’s the negative end of the battery to the spring to the rim of the PCB to the main body tube) in uninterrupted. That means that the path of least resistance will always be that direct path, so you can’t put a smart tailcap in parallel - no current will flow through it.
The second electric path is possible where the e-switch connects. I imagine the e-switch is connected to a pin of the MCU that is set to “input pull-up” with means it’ll be positive with a ~30k Ohm internal resistor connected. Pushing the e-switch connects it to ground momentarily, which the MCU recognizes. I have before (in the D25 headlamp) connected an LED in parallel to the e-switch. That allows for a “dumb” illuminated e-switch. It didn’t work with green LEDs, but worked with blue. I’m thinking because of vF differences. I’d have to do some testing to see if that’s a viable option for an illuminated tailcap.
Doing a “smart” aux board under the TIR (like what Lexel has done) would be much more feasible and predictable.
Edit: Scallywag beat me to the punch, although I included a few different details. Thanks for chiming in (and confirming my initial thoughts).
My first FW3A-series light should be any day now (I think it just passed through customs) so I can poke around more later, but I don’t expect any surprises.
Cool - didn’t know that could work! I was assuming you’d have to grab yet a third current path down there to power the LEDs (ground, of course, being quite freely available on that end of things)
Well… without more testing, I don’t know how dependable it is. I ended up getting rid of my D25 so I can’t test on that one. The different behavior depending on the LED color makes me cautious about this and how it would operate long-term and with different battery voltages.
