So the voltage from the MCU is a steady 2.2v, but somewhere a slight short develops around the switch area which causes the voltage to drop down to 1.6v?
That’s interesting.
No, there’s about 4V coming to the switch assembly (0.2V drop from the diode is about right). The voltage across the 15K resistor is 4V minus the LED Vf. I measured as high as 2.4V on the resistor when there is no light, and 1.7V when there is light.
That means higher current when there is no light. Which makes sense if the current is going around the LED somehow. Next thing I’ll try is removing or moving one of the LEDs which seems awfully close to the switch.
think so
Okay, I see.
I don’t know very much about the chemistry involved in making an LED, but it seems like these little switch LEDs are possibly acting funny when they’re not fed enough current. Maybe they start to leak current past their internal parts. IDK. I’ll leave the technical stuff to others. Lol
I think it is (first production Narsil), the Q8 has the latest version of Narsil and Tom worked really hard getting it done and tested.
I have an earlier variant that I flashed and put in a little FandyFire Rook that uses 4 clicks to lock out… the Emisar D4 and D1 take 6 clicks to lock out! 4 clicks to the D4/D1 (thinking I was locking it out) puts it in a momentary switch tactical mode. I’m presuming the Q8 will also have the 6 click lockout? Or will it be 4 like the earlier versions?
Edit: One thing that confused me was that when I clicked the D4/D1 6 times for lockout (after doing some reading/research) the lights blink 4 times to indicate lockout. Unlocking they blink twice. Seems somehow not intuitive for the number of blinks to not match the required clicks. But now I know. 
Yes, as far as I know.
I'm all confused which thread I'm in, but when the LED's failed to light up. I detected a short from grnd to V+ in to the board, to the resistor. Verified it several times. I think the full parts removal and reflow fixed it all up. The light has been fine now for 27 hours and still running.
OTSM is a nice evolution of the clicky power switch, but I doubt we can write off e-switches yet. For example, a reverse clicky power switch, even with OTSM, cannot keep the LED (s) lighted while the button is held. It’s fantastic at “click to turn on or off”, but it cannot do the other half of the Q8’s core interface — “hold to ramp”. The single most defining feature of the Q8’s UI isn’t really possible with a power disconnect switch.
The switch types can try to emulate each other, but I doubt they’ll ever by fully interchangeable. I implemented ramping on a clicky switch, but it’s not the same.
It’s probably worth mentioning that the Q8 doesn’t use a triple-channel driver.
OR it means that there is additional high resistance adding on in series with the fixed resistor. Voltage across resistor, plus voltage across LED must add up to about battery voltage, less a little bit (i.e. the voltage of the MCU pin, which I anticipate will be roughly battery voltage minus about 0.3V.)
If Vled+Vr doesn’t add up to the full amount, additional voltage drop must be occurring elsewhere (poor joint, internal PCB problem etc.)
Tom, if there was a short there, you wouldn’t measure any voltage across the LED at all. Or the resistor.
And for one of the most important thing. The Q8 draws over 20A in turbo. A clicky switch does not like high currents like that. With E-switch you can easily turn on and off 30A current because the electric components of the driver do the switching, but a clicky will melt down.
In Narsil’s ramping UI, 4 clicks from off activates lockout.
In Narsil’s mode set UI, lockout is mapped to 2 short clicks and a long click.
The Emisar 6-click thing (and 4/2 blink thing) seemed strange to me too, but I didn’t change it… generally tried to minimize changes, especially ones which didn’t match the project’s specifications. However, I’ll send you some firmware showing how I prefer to do it instead.
Although most shorts change a connection from near-infinite resistance to infinitesimal resistance, it sounds like this may be more of a middle ground.
Even a partial short would cause problems on such a sensitive circuit; the smallest trace of conductive material in the wrong place could alter the voltage enough to interfere with the switch LEDs. For example, even an oily fingerprint on the PCB could potentially decrease resistance enough to cause intermittent misbehavior on a particularly sensitive circuit. Or if there was metal dust in the air during assembly, some could stick to the PCB in the wrong places.
Ah yes, that's just the TA SRK board. uhm.. well I couldn't really find a circuit layout for the Q8. Is there one around here? Wasn't this kind of stuff once in the first or second post? It's a piece of cake to define a new builld with different channels and pins, but I have to know what they are first. Of course I like the tripple channel modes, so I might make a new modegroup that re-maps them to one or two ramps, easy.
Agreed, a “partial short” across the whole circuit, (I think that’s what Tom reported) could drag down the MCU output to the point where the voltage across resistor+LED dropped too low, but not just an oily fingerprint (The MCU output pin can drive quite hard, rated for 10mA, max rating 40 mA. and I expect there is more to come even beyond that)
Contamination across the LED could be a plausible cause of a small leakage current, comparable with that set for the LED (150uA-ish) which bypassed the diode and dragged it’s voltage down. If so, a thorough cleaning of the PCB with e.g. IPA and a bristle brush ought to remove any obvious contamination.
Additional resistance in series due to a poor intermittent joint or internal PCB fault (via.) is also another potential mechanism.
In any of these scenarios a basic measurement of voltage across diode, voltage across resistor, battery voltage, and voltage between ground and the end of the resistor connected to the MCU, might be sufficient to narrow it down to which, if any, of these things might be happening, when the LEDs are misbehaving intermittently.
TK good point about OTSM switch cannot do ramping the same way. I'd still prefer a clicky, even for a ramping UI. Off is still off as it always will be and must be. Sure that means you probably need short tap to initiate a ramp, so can't use that for off, but you still have full cllick for off, so, it just means you don't have to hold the button down while it ramps.
Dale, the Emisars don’t actually use Narsil. It’s based on Narsil, but with a lot of small changes. I don’t know if it’s been given its own name yet. EDIT, (It’s called RampingIOS… but people mostly just call it “D4”.)
The Q8 uses NarsilM v1.0
It’s 113uA, if that makes a difference.
DEL has posted a schematic on the modding thread.
Even he’s not sure whether it exactly represents what has been produced.
Depending on battery voltage, 10% resistor tolerance, particular diode Vf at that current, etc. etc. 
OK, well I didn't find an actual schematic but the first board trace image I could find googled up on candlepower. Looks like a BLFA6 layout no? I will conjure up an eswitch build with TA modegroups, or something similar-ish, for a BLFA6 board. Should take all of 3 minutes, mostly to figure out how the ramps should look.