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

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

I’ve worked on this before and the layout did not work decently. In the past I depended too heavily on the LFPAK outline I grabbed from the internet. When I saw RMM take a crack at the problem (#3441) the truth is I initially dismissed his work: I thought to myself “shows what he knows, that stuff won’t fit.” Later the idea kept rattling around in my head again and it occurred to me that both RMM and I have built the A17DD-SO8 drivers and know exactly how much space each component needs. Clearly I needed to reconsider. Knowing how large the actual components are once installed on a driver like this makes a difference (as one might imagine :p).

Features:

  • ~1.0mm ‘tall’ component keepout around edge. (7135 tab extends to no closer than 0.5mm of the edge.)
  • FET + 1*7135: alt PWM is hooked up to the single 7135 so it may be possible to get this working with an unmodified version of STAR. Smile
  • No Zener! Sorry MT-G2 folks, you’ll have to stack a Zener across C1 or between D1 and R2. Or maybe kind of wedge it between R2 and the FET.
  • Offtime ready.
  • Large 1.5mm GND ring on bottom and on top (where possible). Exposed copper is 0.5mm on top and bottom.
  • Like some other recent drivers, this driver does have a reverse-polarity protection diode but bypasses the diode for the voltage divider. Due to this we are able to use any diode desired. Ideally we use a protection diode with as low a Vf as is reasonable.
  • The exposed spring pad is 10mm. Total pour diameter is 12mm.
  • LED +/- pads are 2.5mm in diameter. They’re on much larger pours and diagonally across from one another.
  • Some symmetry & stuff here and there.

v009:

https://oshpark.com/shared_projects/7sNNyipn

v002 WIP screenshot (just for show-and-tell):

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

Edited by: wight on 01/18/2015 - 15:39
wight
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I’ve worked on this before and the layout did not work decently. In the past I depended too heavily on the LFPAK outline I grabbed from the internet. When I saw RMM take a crack at the problem (#3441) the truth is I initially dismissed his work: I thought to myself “shows what he knows, that stuff won’t fit.” Later the idea kept rattling around in my head again and it occurred to me that both RMM and I have built the A17DD-SO8 drivers and know exactly how much space each component needs. Clearly I needed to reconsider. Knowing how large the actual components are once installed on a driver like this makes a difference (as one might imagine :p).

Features:

  • 0.5mm component keepout around edge. I may trim this up to a larger number in future revisions..
  • FET + 1*7135: alt PWM is hooked up to the single 7135 so it may be possible to get this working with an unmodified version of STAR. Smile
  • No Zener! Sorry MT-G2 folks, you’ll have to stack a Zener across C1 or between D1 and R2. Or maybe kind of wedge it between R2 and the FET.
  • Offtime ready.
  • Large 1.5mm GND ring on bottom and on top (where possible). Exposed copper is 0.5mm on top and bottom.
  • Like some other recent drivers, this driver does have a reverse-polarity protection diode but bypasses the diode for the voltage divider. Due to this we are able to use any diode desired. Ideally we use a protection diode with as low a Vf as is reasonable.
  • The exposed spring pad is 10mm. Total pour diameter is 12mm.
  • LED +/- pads are 2.0mm in diameter. They’re on much larger pours and diagonally across from one another.
  • Some symmetry & stuff here and there.

v003:

https://oshpark.com/shared_projects/I16olxS2

v002 WIP screenshot (just for show-and-tell):

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

wight
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  • Pulled components back in for an ~1.0mm ‘tall’ component keepout around the edge. (7135 tab extends to no closer than 0.5mm of the edge.)
  • Changed LED+/- pads from 2.0mm to 2.5mm
  • Revised silkscreen (added orientation mark for MCU, moved identifiers, increased text size, etc)
  • Removed ‘stop’ designation on BAT+ vias for aesthetic reasons. (.. aesthetic reasons is also why they were on the stop layer in the first place, heh.)
  • Changed 7135 outline to one which has a center pin.

v006:

https://oshpark.com/projects/s0JdAzw7

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

DB Custom
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Y’all are Killin me!

Dale

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DBCstm wrote:
Y'all are Killin me!

Oh yeah? It is only just beginning Tongue Out

It's the simple things that we take for granted that cost us the most

Ευκαιρία λέει πιάσε με από το μέτωπο γιατί μόλις έχω περάσει δεν θα με πιάσειs

pilotdog68
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So it’s titled WIP, but how close is this to “release” status?
.
.
My X6 triple project is begging for it…

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

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

wight
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pilotdog68 wrote:
So it’s titled WIP, but how close is this to “release” status?
.
.
My X6 triple project is begging for it…
It looks fine to me. I’d have no qualms about ordering the PCBs if I were you. It’s possible that I’ll continue to make some minor tweaks, but the design looks good in Eagle and on the OSH Park previews.

As far as I’m concerned it’s a WIP until at least one revision is actually assembled and working.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

pilotdog68
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Hmm I don’t suppose you have a parts list/shopping cart for it?
.
I might just wait till someone smarter than me tests it

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

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

wight
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Exactly the same cart as the A17DD-SO8, plus a single 7135. Smile Refer to page 2 of the AxxDD-SO8 thread for the cart links.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

pilotdog68
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Nice. All of the different FET types flying around has got my brain in knots. Sharing = Simplicty

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

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

wight
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I forgot to mention that those vias are extremely close the the edge of the board. If there was a problem, that’s where I’d expect it to be. That’s something I expect to tweak. I don’t think that OSH Park will fail to plate the vias, but the GND vias do not meet OSH Park’s design rules. Assuming that the vias are drilled and plated this could result in only partial plating of the through-hole itself. It will certainly result in the vias not being entirely surrounded by copper on at least one side of the PCB (the bottom side). I expect the line to cut directly through the middle of the vias. What I expect is to see something like what led4power gets over here (but slightly worse): http://budgetlightforum.com/node/34812

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

WarHawk-AVG
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Nice..single 7135 for low modes and a FET for DA POWAH!

Awesome build wight…good job!

DB Custom
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12 Ordered, oh boy, maybe I get to do a batch at one time again!

Which reminds me, stencil….

Dale

DB Custom
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Wight, for whatever reason the board outline doesn’t line up with the components when uploaded to OSHStencils.com. Really doesn’t matter as the actual cut out’s will be aligned with the pads to use it, just thought you’d like to know something is off somewhere.

I don’t understand it, just use it and report it. Wink

Dale

cajampa
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Very nice wight, feels very balanced with the max POWAH and battery saving lows, i can’t wait to see someone build it,
Would these work just like a A17DD-SO8 if the 7135 pad is not populated?

It would be very interesting to see a comparison on run times for the FET on low from a A17DD-SO8 and this one.

EDIT
And Happy New Year Party guys

DB Custom
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I got 5 of those fancy mosfets, I think I’ll try em on these drivers and see how they work out.

(That would be the SIR800DP)

Dale

pilotdog68
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Are the moon/low modes on the usual FET drivers really that bad?

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

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

DB Custom
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Around 4-5 lumens. A lot of folks don’t consider that to be a moon…it needs to be sub lumen for that.

Dale

wight
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pilotdog68 wrote:
Are the moon/low modes on the usual FET drivers really that bad?
If you’re going for truly low then the range of battery voltage from fresh to empty is an issue. PWM levels which barely light an LED on a full cell (~4v) will not light an LED with an empty cell (3.0v to 3.5v). The 7135 should help with that.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

wight
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WarHawk-AVG wrote:
Nice..single 7135 for low modes and a FET for DA POWAH! Awesome build wight…good job!
Thanks WarHawk-AVG! I’m not sure that we can’t do better. I’d love to see it get a little more symetrical if possible and shrink a little tiny bit so that the GND ring vias can move inward.
cajampa wrote:
Very nice wight, feels very balanced with the max POWAH and battery saving lows, i can’t wait to see someone build it, Would these work just like a A17DD-SO8 if the 7135 pad is not populated? It would be very interesting to see a comparison on run times for the FET on low from a A17DD-SO8 and this one. EDIT And Happy New Year Party guys
Thanks cajampa! Again, the actually cramming all of this onto one PCB wasn’t something that I thought could be done before I watched RMM do it.

Yes, these will function like an A17DD-SO8 unless you do something to make use of the extra hardware.

DBCstm wrote:
Wight, for whatever reason the board outline doesn’t line up with the components when uploaded to OSHStencils.com. Really doesn’t matter as the actual cut out’s will be aligned with the pads to use it, just thought you’d like to know something is off somewhere. I don’t understand it, just use it and report it. Wink
We’ve seen this before, it’s not really clear to me why it happens. I did change CAM jobs, but I don’t know whether that is related. If I remember maybe we’ll try a different CAM and see if it does the same thing.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

cajampa
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DBCstm wrote:
I got 5 of those fancy mosfets, I think I’ll try em on these drivers and see how they work out.

(That would be the SIR800DP)

I look forward to see the result of this, i know we can’t hope for much more, but for me who just got in to this game and still dream of more lumens Smile the possibility is exiting.
And now we suddenly have the possibility of more max and lower low with proper long runtime if i understand things right.
All in a single sided easier to make driver.

And i would think that if there is less resistance in the driver with this more expensive FET it should get less hot also.

wight
Yeah i saw RMM thread but i don’t know if he released any ospark project for it and he said it was untested, anyway that is what i so enjoy about this place, the unrestrained intuition that runs in and out in these threads, where so many ideas are an iteration of something before.

Does the FET get shut of when it is using the 7135 for lower modes?

pilotdog68
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wight wrote:
Yes, these will function like an A17DD-SO8 unless you do something to make use of the extra hardware.

So theres really no reason to buy both boards right (except for Zener option)? I can just buy multiples of this one and use it for either driver?

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

Major Projects:  Illuminated Tailcap, TripleDown/TripleStack Driver

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Quote:
And i would think that if there is less resistance in the driver with this more expensive FET it should get less hot also.

Less resistance in the driver just allows higher current when the cell is fresh. The heat comes from the led so more current would mean more heat not less.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

DB Custom
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Oh Boy! More heat! Bring it!

That’s what I’m always looking for, hotter, brighter, whiter… a dragon slaying cell munching annihilator of a light! Smile

My son want’s to know the difference between disintegrate and vaporize. :bigsmile:

Dale

cajampa
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Rufusbduck wrote:
Quote:
And i would think that if there is less resistance in the driver with this more expensive FET it should get less hot also.
Less resistance in the driver just allows higher current when the cell is fresh. The heat comes from the led so more current would mean more heat not less.

I meant that the driver should get less hot or is that never an issue on the FET drivers? i thought it was recommended to at least use a silicon cube on them.
I know the led would get more current thats what i am hoping will happen.

wight
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pilotdog68 wrote:
wight wrote:
Yes, these will function like an A17DD-SO8 unless you do something to make use of the extra hardware.
So theres really no reason to buy both boards right (except for Zener option)? I can just buy multiples of this one and use it for either driver?
Pretty much.
  • The A17DD-SO8 is easier overall to hand-build than this driver.
  • One difference that stands out to me is the way LED+ bypasses are done on both boards. This PCB should be reasonably friendly to drilling a hole between C1 and the MCU without interfering with an SOIC clip much. The A17DD-SO8 can be drilled in the center of the PCB and hopefully not interfere with an SOIC clip.
  • I don’t think that there is space for an LDO on this design, so I do not expect to produce a 17mm LDO version for momentary usage like I did for the A17DD-SO8.

Rufusbduck wrote:
Quote:
And i would think that if there is less resistance in the driver with this more expensive FET it should get less hot also.
Less resistance in the driver just allows higher current when the cell is fresh. The heat comes from the led so more current would mean more heat not less.
I give all of that a big meh. I’ve already made it clear in the AxxDD-SO8 thread that I don’t think lowering MOSFET resistance further will result in much/any more current. I’ll be happy to eat my words, but I would recommend against getting excited. I also agree with RBD: AFAIK the MOSFET isn’t producing a significant amount of heat. It should be stone cold.

EDIT:

cajampa wrote:
Rufusbduck wrote:
Quote:
And i would think that if there is less resistance in the driver with this more expensive FET it should get less hot also.

Less resistance in the driver just allows higher current when the cell is fresh. The heat comes from the led so more current would mean more heat not less.
I meant that the driver should get less hot or is that never an issue on the FET drivers? i thought it was recommended to at least use a silicon cube on them. I know the led would get more current thats what i am hoping will happen.
The silicone cube is for a linear driver’s FET, not a DD driver’s FET. FETs don’t really produce heat when they are on or off, only when they are in between on and off. The linear driver purposefully keeps the FET in this “between on and off” region in order to regulate current. Doing so produces a lot of heat, but that only applies to linear drivers.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

cajampa
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Thanks wight for clearing up my confusion, you are correct i had confused the two.
And now i know that a DD’s FET driver is stone cold, i had thought heat could be a problem nice that it is not.

Is it possible to make a linear driver with this kind of FET and the attiny? or is that another animal altogether Smile

wight
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cajampa wrote:
Thanks wight for clearing up my confusion, you are correct i had confused the two.
And now i know that a DD’s FET driver is stone cold, i had thought heat could be a problem nice that it is not. Is it possible to make a linear driver with this kind of FET and the attiny? or is that another animal altogether Smile
You’re welcome. Yes, it is possible AND yes it is another animal altogether. The driver is a WIP: A20LDX / A17LDX. The circuit / schematic has been tested and functions (to some degree or another).

Also note that led4power has built a linear driver called the LD-1 using this sort of FET and a PIC MCU rather than an ATtiny13A. All modes are constant current without PWM. Led4power’s driver is available for sale: http://budgetlightforum.com/node/34812

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

Crux
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I'm still not used to the lack of a bypass cap at the aTtiny's power pin (from pin8 to Gnd). My designs at work could save a lot of cost and space if IC's didn't require bypass caps... But, there are a million of these drivers out there - so its hard to argue. I'll always find a way of adding these caps.

Crux

wight
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Crux wrote:

I’m still not used to the lack of a bypass cap at the aTtiny’s power pin (from pin8 to Gnd). My designs at work could save a lot of cost and space if IC’s didn’t require bypass caps… But, there are a million of these drivers out there – so its hard to argue. I’ll always find a way of adding these caps.

Crux

Your PCBs at work probably have a higher component count… this one uses 8 components. The whole circuit is 10 components! My (feeble) grasp of this stuff tells me that our only source of noise is the battery’s behavior under load. Note that even on a stock Nanjg-105c they do not use the normal “1uF for every IC” but rather >3uF! Apparently that’s because there’s some bulk component to this. As long as our little cap is close enough to the MCU vs the LED I suppose inductance keeps things in check. <shrug>

You can use the cap in the normal way (with positive connected between the protection diode and the MCU), but you’ve got that boost circuit problem at that point. To fix that you’d need a Zener diode pulling the boosted voltage back down on the MCU side of your bypass cap. By that time you might as well have implemented an LDO and used the output cap on that in lieu of the bypass cap.

Still taking a break. Smile
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

RMM
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The design does work, and it works pretty well.  The efficiency is nice on the lower modes, with a nice glowing moonlight mode.  I recommend running the 350mA binned 7135s if you want the lowest possible moonlight mode.  In general, it seems like you can get a lower stable moonlight mode with it than you can with the 380mA binned variety.

For my design I had to swap the PWM outputs in the firmware, but it looks like you won't have to do that.  

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