[WIP] 17mm DD+single-7135 driver / single sided / Dual-PWM

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ToyKeeper
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BTW, any ideas on how to enable a bleeder to leak power to a lighted tailcap while off, without interfering with OTC drain? Or how to influence the rate of OTC drain?

Also, any thoughts on how to reduce power fluctuations at the MCU when the main FET power circuit is repeatedly going from zero to a zillion amps? It seems to have sort of a splash effect, and the tiny25/45/85 chips aren’t as splash-resistant as the tiny13.

wight
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ToyKeeper wrote:
BTW, any ideas on how to enable a bleeder to leak power to a lighted tailcap while off, without interfering with OTC drain? Or how to influence the rate of OTC drain?

Also, any thoughts on how to reduce power fluctuations at the MCU when the main FET power circuit is repeatedly going from zero to a zillion amps? It seems to have sort of a splash effect, and the tiny25/45/85 chips aren’t as splash-resistant as the tiny13.

RE: point #2 – that’s what post #300 is really about. Tom E has combated that effect by adding a ton of capacitance (20uH total), but I feel like that’s a bandaid type solution. I’m very interested in comments on what I’ve drawn up and shown in post #300.

RE: point #1 – crap, I felt like I was forgetting something as I worked on this board. Adding a that tailcap-led-setup was on the to-do list. I just looked it up… apparently pilotdog68 has just been putting a 560 ohm resistor across BAT+/BAT- on the driver.

EDIT: also, my thoughts on influencing the rate of OTC drain are still what they were a few days ago in the A17DD-SO8 thread. What I said over there was that it might be better to increase the capacity of the OTC by an order of magnitude or so and then use a bleeder resistor of our choosing. Clearly this PCB is going to get crowded with all that stuff (especially because a good 10uF cap for the application will be 0805 or larger). I also haven’t thought this idea all the way through at all, it may not really make sense once I put it on paper. I suspect that I’d better think some more and look at the datasheet. In the meantime if someone wants to play around with it they are welcome to do so. It would be a straightforward thing to experiment with.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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Tom E
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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.

wight
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Tom E wrote:
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!
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.

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Yep, I'm clueless with this stuff - I kind of/sort of understand you -- just forget bout my attempt analysis Smile.

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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

wight
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Tom E wrote:

Yep, I’m clueless with this stuff – I kind of/sort of understand you — just forget bout my attempt analysis Smile.

Meh, I still listen anyway. Wink
Flashy Mike wrote:
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
I’d say to check R1/R2 and all the pins Pin 7 on the MCU.

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wight wrote:
I’d say to check R1/R2 and all the pins Pin 7 on the MCU.

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!
wight
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Flashy Mike wrote:
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!
That’s great. 14 amps is impressive. What emitters are you using?

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wight wrote:
What emitters are you using?

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 …
ToyKeeper
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wight wrote:
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.

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?
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ToyKeeper wrote:
wight wrote:
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.

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?

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wight
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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-)

ToyKeeper wrote:
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?
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.

DavidEF wrote:
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?

Just put them in series as necessary with an appropriate current limiting resistor.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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wight wrote:

1. The tail LEDs are a huge drain,they don’t need much help to flatten your battery…

2. But yes, double trouble if a person did both a zener e-switch and a tail LED setup.


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.

My Favorite Modded Lights: X6R, S8 , X2R , M6, SP03

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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Finally, BLF is back online. Yay!

@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.

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chouster wrote:

@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.

For the record I think TK measured the Attiny by itself taking more than 0.1ma, but we’ll see. Those boards were shipped to me yesterday.

My Favorite Modded Lights: X6R, S8 , X2R , M6, SP03

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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pilotdog68 wrote:
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.
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.
Sad

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?

chouster wrote:
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? With the recent drivers I thought about stacking four 0.22µF C0G rated caps as an OTC, you think this might work (/ makes sense)? 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 a magnitude lower than that, at least, if everything optimized for that.
  • Thanks. Wink
  • 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?

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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wight
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pilotdog68 wrote:
chouster wrote:

@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.

For the record I think TK measured the Attiny by itself taking more than 0.1ma, but we’ll see. Those boards were shipped to me yesterday.
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…

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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chouster
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Thanks for the answers guys!

@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.

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chouster wrote:
Thanks for the answers guys! 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. Smile From what I’ve read in the past I think that should be very promising.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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wight wrote:
pilotdog68 wrote:
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.
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.
Sad

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?


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.

chouster wrote:
@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’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.

My Favorite Modded Lights: X6R, S8 , X2R , M6, SP03

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

wight
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pilotdog68 wrote:
[snip]
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.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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I have a lambda keylight. It’s brighter than a tritium vial, but not by much.

As for low power mode on a tiny13, it remains to be seen what the lower limit is. It’s easy to get down to 0.3mA,but the goal is lower… Anyway, I doubt we’ll average lower than the 0.15mA tail boards people already made. The main appeal is that it can do fancier things, like changing color with voltage.

wight
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Some progress on moving the spring bypass via up to 3mm diameter. My thought here is that a larger diameter via will reduce the chances of the wire folding over, binding, etc.

EDIT: I have no idea where the component designators are going to fit.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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wight
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This looks decent… No guarantees that it’ll work though.


https://oshpark.com/shared_projects/4nsRthrB

Stuff:

  • 3mm bat+ spring bypass wire hole.
  • Pin3 pad available for scraping. (1.4×1.8mm triangle)
  • ~1mm physical keepout around the edge of the driver
  • >0.5mm electrical keepout around the edge of the driver
  • Placement is “a little” tight.

Parts list:

  • C1 – 1uF, maybe much more depending on stability (5uF). [0603 – decoupling capacitor]
  • OTC – 1uF X7R. Maybe much more (10uF) if used w/ R5 pulldown. [0805 – off-time capacitory]
  • R1 – whatever
  • R2 – whatever
  • R3 – 200 ohm or so. [0603 – Zener load resistor]
  • R4 – 560 ohm or so. [0603 – tailcap LED bleed resistor] [not needed w/out tailcap LED circuit]
  • R5 – unknown value [0603 – OTC pulldown resistor]
  • R6 – 12k-ohm [0603 – FET gate pulldown resistor] [used to prevent flash when moving to moon mode]
  • D1 – protection / stability diode. Do not bypass. [SOD-323 Schottky Diode]
  • Z1 – snubber diode. Do not bypass. [SOD-323 Zener Diode]
  • MCU: SSU or SU w/ legs bent (eg our normal narrow MCUs, like v009 and most other BLF drivers)
  • FET: Power-SO8 (eg our normal FETs, like v009 and many other BLF drivers such as A17DD-S08)

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

ToyKeeper
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Interesting. I’m not sure what all the changes are about though. Why is C1 smaller? Can Z1 and R3 be safely omitted? Do you think R5 will reduce run-time efficiency in the same manner as R4? What are the effects of moving D1 away from C1 (and it looks like their logical arrangement has changed too?)?

wight
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D1 and Z1 are both specifically marked in the partslist as “do not bypass” because I figured that question would come up! Silly Big Smile

Firstly, I haven’t tested this circuit at all or even chosen real parts for it. I could easily be wrong about how low we can go with C1 (that’s mentioned in passing in the partslist too). The thinking is that C1 on existing BLF DD & linear drivers is currently vastly oversized for regular “decoupling” and is more along the size of “bulk capacitance”. We need a lot of bulk to dampen the really harsh spikes. If we eliminate the spikes, bulk capacitance needs are reduced. For 1s use Z1 should be populated with a Zener in the range of 4.5v to 5.5v breakdown voltage. The plan is that this diode will burn off the spikes. For 1s applications R3 should probably be bypassed (shorted), but I do not know that for certain.

I haven’t done any math or significant thinking in regards to the OTC pulldown (R5). I think that it will be a high-value component, so it’s effect on runtime efficiency will likely be similar to that of the voltage divider.

RE: moving C1 and changing the arrangement/orger of C1/D1… yes, you are correct. At some point during BLF DD driver development problems started cropping up. Comfychair spearheaded the effort to track down the problem and eventually nailed down what was going on in this thread: comfychair – FETs and gate resistors – scope images The problem turned out to be an inadvertent boost circuit. We eliminated the boost circuit by moving the decoupling capacitor to the “wrong” side of the protection diode. My intention with this revised circuit is to allow the small & constant “boost” to happen, but burn off the extra voltage through the Zener.

Furthermore, the closer the decoupling cap is to the component it “decouples” the better. C1 is now right next to the MCU – this is good. It’s also fed by a long & thin trace. In my book this is also good because it may provide a little inductance to keep things smooth.

if the supply voltage wasn’t so wonky th

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

comfychair
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C1 location had no effect on the original (boost-prone) circuit. Remember, I even tried it soldered direct to the leg of the MCU. After C1 was moved Vcc & B+ tracked together exactly 1:1, minus the difference of the drop thru the diode. Are you thinking you can get Vcc to stay flatter than B+? I don’t think that’s possible.

A second capacitor in parallel with D1 also worked just as well as relocating C1, but that increased the part count.

I don’t really feel like building one, but if you wanna send me one with the new layout I’ll get some scope pictures of it to compare the shape of Vcc to the other designs.

chouster
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Oooohh! Another comeback of a BLF-legend! Comfy, thanks for all your great contributions in the past. Welcome back.

comfychair
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comfychair wrote:
Are you thinking you can get Vcc to stay flatter than B+? I don’t think that’s possible.

Oh, I see now that it is possible… you’re planning for Vcc to stay above B+, but only by a controlled amount that doesn’t zap the MCU. Is there anything to gain from that though? Have there been any problems caused by the swing in Vcc? I’ve been AWOL too long, I don’t know any of the new firmwares or the DD+7135 drivers.

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