Ohh btw, I pulled the C1 cap off of a SS/Cu X5 (based on this FET+1 design) using a ATTin25, and tested it - best I can tell it's a 12 uF cap. On my DMM, 10 uF caps tests at ~9.6 uF, 22 uF caps also tested a little lower, so the cap off the SS/Cu X5 board tested at 11.5 uF.
Sorry, but I'm not sure I understand enuf to comment on your proposal. But also I would like to make it clear I don't care about 13A's any longer - only interested in 25's and 85's. I consider 13A's obsolete now - all I've been working on over the last few months is 85's (e-switch based) and 25's clicky based. I don't mind the 13A footprint because the bent pin setup for the 85 works well, but I do want an 85 to work reliably in a high powered setup, preferably with the SIR800DP FET. Raising the value of the cap seems to fix the problems - I've had these problems on pretty much every 25 and 85 board I've built (maybe 15-20), seems like. It may be a bandaid, true, but it's the only bandaid that works reliably. I didn't do this on my own - it was recommended by EE's, both here on BLF and at work here. I was just the one trying it, testing it.
Edit: wait... from what I recall, it was recommended the cap be as close to the MCU Vcc pin as possible, and this is what you did here. Also a big cap after the diode could be trouble, but the smaller cap you are using is a good thing for sure. Hhmmm. This may address issues the EE's raised - you might be good goin in this direction, but I dunno much bout these things, but dang - looks pretty good!
One of my other "fixes" that worked was adding a 0.1 uF cap across the MCU pins of grnd to Vcc. I literally have the cap sitting on top of the MCU wired that way, and actually can still clip the MCU and re-program it. This was my typcial "fix" for my e-switch Narsil based 85 FET+1 v009 drivers, and seemed to work, accept for the last one over the weekend -- had to double up the 10 uF cap to get it working.
Thanks for the [unquoted] info Tom E. As for the quoted bit… I’m pretty sure that it’s the wrong analysis. The issue w/ a cap after the diode in previous FET/DD setups was that there was enough inductance in the circuit to get an unwanted boost circuit with the diode followed by a cap. I think that a smaller cap would actually tend to make this worse if everything else was left the same. In this case everything else is not left the same, I’ve added the Zener/resistor combo to hopefully get rid of the extra voltage from the [unwanted] boost circuit. The boost circuit is certainly still there, the extra volts are just getting dumped by the Zener. At least that’s the plan.
Using big caps to get rid of unwanted voltage spikes isn’t inherently bad AFAIK, but in our case it’s not something that we necessarily have a lot of space for. Replacing 1 extra 0805 cap with 2 extra 0603/SOD-123 sized components isn’t necessarily the greatest achievement in the world (heh), it’s just something to chew on. Without putting an oscilloscope on the circuit and checking things, I suspect that if this circuit works as intended it may also clamp the voltage better and tolerate bigger spikes. And of course it adds pads for a Zener.
In one of my lights with this driver the voltage indicator only works when the light is hot. Probably a bad solder connection. Since I can’t find a circuit diagram - could someone point me to the most suspect components?
Thanks
Michael
Thanks!
Finally I resoldered all pins of all components. Everything ok now, got even 2 more amps. 14 amps in total now with my triple Convoy S2+. Of course I could use this light as a soldering iron after 30 seconds …
Great driver!
3x XP-L HI U6. With full LG HE4 battery. I use this battery in this light only for tests, it gets too hot. Protected Keeppower 2900 for daily use give a max of 9 amps, 18350 efest purple even 10 amps. Still plenty …
BTW, I’ve heard a few times not to use a zener on an e-switch light since it drains power in standby mode. Would the same apply to a clicky with lighted tail, or is it pretty much irrelevant since the standby power should mostly be going through a bleeder instead of the rest of the circuit?
I’d think you’ll have a different problem: How will you reconcile the voltage of the series cells to the Vf of the tailcap lights? Are you using 6v tailcap LEDs or putting two (or more) in series to get the forward voltage up?
Here is the latest iteration on the A17DD-L. This version uses mostly 0603 sized passives and has a lot of stuff…
The new, proposed, Zener for 1s setup.
0805 OTC + 0603 pulldown
0603 bleeder for PD’s tailcap LEDs
Pin 3 pad as requested by Tom E
Maintains 1mm physical keepout for components and 0.5mm non-GND keepout.
2mm BAT+ passthrough
Of course it’s still looking a little rough, but DRC seems to be OK. (Yes, I’m aware that the 7135 needs to be attached to LED-)
For a 1s e-switch application the intention is to use a zener with a higher breakdown voltage than battery voltage. (5v) This should prevent the problem you are thinking of for an e-switch. For multicell applications an e-switch with a zener is still a mistake!
The tail LEDs are a huge drain,they don’t need much help to flatten your battery… But yes, double trouble if a person did both a zener e-switch and a tail LED setup.
For multi-cell clicky applications with a zener and tail LEDs… Yes, the Zener will play a roll. I’m not certain, but I believe that the Zener’s roll will be small in comparison to the drain from the tail LEDs.
Just put them in series as necessary with an appropriate current limiting resistor.
1. Well, it depends on your definition of “huge” and how bright you like your tail led’s. They can be taken down as low as 0.1ma and still be useful with dark-adjusted eyes. I have seen some e-switch lights have much higher vampire drain. 2. Tail led’s are normally used on clicky lights, not e-switches, but even so I’m not sure on this. I would think the tail led’s could just use the leakage from the Zener, and not have to bleed off any more current than was already leaking.
@wight, very cool to have you back! Looks like a nice board, although I don’t understand why you did this and that, but that’s simply because I don’t know much about electronics.
I like that you kept the OTC in 0805 size, so we could go to a higher value OTC, if needed, without loosing X7R,10%, 25 VDC ratings, right?
(edit: that’s what you mentioned in comment #303)
With the recent drivers I thought about stacking four 0.22µF C0G rated caps as an OTC, you think this might work (/ makes sense)?
(edit: that’s stupid, hard to find and way too expensive in 0805 size.)
The additional zener is not meant for a 2s setup. Of course that’s what most of us are thinking when reading “zener”… Is it some kind of what they call flyback-diode?
What’s the purpose of a OTC pull-down resistor?
Sorry for asking so many (dumb?) questions…
@PD, I think with your new smart (MCU controlled) tailcap, we could reach power consumptions an order of magnitude lower than that, at least, if everything optimized for that.
I agree, huge is relative! I definitely consider anything which can flatten an 18650 in a year “huge” when it comes to quiescent current. Clearly a 3Ah cell should give about 3yr on a 0.1mA draw, I think it’s fair to call that “not huge”… With that said, the few photographs I’ve seen are of tailcaps which appeared to be weeellllll over 0.1mA or even 1mA! Is anyone running a setup which has been measured in the 0.1mA range? I apologize for the fact that I haven’t had a chance to read through your thread yet. I haven’t been able to read entirely through my own threads either.
FWIW I believe that Lambda claimed to have achieved as low as 0.009mA with some Keylights using hand-binned ultra-low-power LEDs. There was fairly extensive information posted somewhere but I can’t find it now. It was probably on the defunct Lambdalights website. At least some of the discussion is available on flashlightnews.net so scrounging there might turn up interesting info. Those lights were using a clear lens, but who’s saying that we couldn’t machine acrylic buttons to use in place of rubber tailcap boots?
Thanks.
Yes, I did leave the 0805 pad for the OTC specifically to allow the use of high-spec parts. IIRC we should not need anything beyond X7R.
The addition of the OTC pull-down is to allow for very high capacity capacitors (such as 10uF). Without a pulldown they’ll stay charged up too long. I posted about this idea in the A17DD-SO8 thread, it may not be good/useful at all.
Yes, now that you mention it that is the proper term. I normally think of it as a clamp. Now that you jar my brain a little, I wonder if we shouldn’t use a 0-ohm shunt in place of the resistor in this case (1s use as a snubber/clamp/flyback). I guess if it looks good on the scope with a resistor then that’s what we’ll continue to recommend. I’d rather leave the pad in place since it’s good for 2s+ use.
Why would an MCU reduce power consumption on the tailcap LEDs?
I think that in PicoPower sleep it can do better, but it also can’t achieve much while it’s asleep… the watchdog timer can wake it up as I recall, to handle blinks or whatever…
@wight, I meant a MCU that’s on the tailcap board. It doesn’t make the LED more efficient, of course, but it could let them stay off, only blinking every x seconds.
@PD, with everything done to reduce power consumptions (ADC off, etc…) in power-down mode, the 13A should draw about 4-5µA during sleep. See figure 19-14 on page 131 in the datasheet. For example take a look at this guy’s project, he achieved that low of a value.
That makes sense. I drew a mental blank when I asked you the question about the MCU of course - by the time PD replied I was back on track, hence the Picopower comment. From what I’ve read in the past I think that should be very promising.
I find 0.15ma gives a very usable level, and Dale and others agree. I have one at 0.06ma right now, but it needs to be turned up just a wee bit. With the latest boards we should be able to make them much more efficient, because less light will be lost down in the tailcap. Also, as battery voltage goes down, so does the draw as well, which really lengthens the time before a battery goes totally flat (I’m sure you could have deduced that, but maybe you hadn’t thought about it).
The ones in the Kronos groupbuy are configured to to around 0.7ma, which I find unrealistic for actual use, but it makes a for a fancy feature to show off.
I’m not familiar with any of the lambda stuff at all.
That’s very impressive. Unfortunately we will also have a voltage divider leaking current past our mcu, but I can’t wait to find out how low we can go.
I forgot that the lower battery voltage would reduce the current. Lambda also factored that in. This is something that edges in and out of my thought process. Purely for simplicity’s sake I often just do my back-of-the-napkin math at 3.7v per cell. : - /
If you aren’t familiar with Lambda’s stuff it would be worth scratching around. Lambda (lambdalights) did the Varapower series of modified Maglites which encompassed several interesting things. One byproduct was a tiny indicator light intended to replace a GITD or tritium pendant. That’s the Keylight series. Here is a link using Internet Archive’s Wayback Machine
I like the direction that your newer tail-LED boards have taken (replacing the washer).
The voltage divider shouldn’t leak much by itself, but requires ADC & stuff to be enabled. Using ADC also almost certainly requires the MCU to run longer when it wakes.
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From what I’ve read in the past I think that should be very promising.