Toroids and MOSFETs and firmware, oh my! (aka:'Tiny13+N-FET=???')

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comfychair
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"60A" means nothing here, it's still limited by the battery voltage. If the cell connected straight to the LED won't do more than 6A, no FET in the world will be able to do more. That's also why the FET's Rds(on) is so critical in a single-cell driver. You could use a FET rated for 10,000A and it still wouldn't do more than what it does without the FET in the circuit.

Rufusbduck
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It’s a way to have virtually direct drive high but with modes as well without having to slave umpteen boards together. The downside is that in parallel led set ups you lose the ability to control the current to each led. Not the end all solution but it still fills an empty driver nitch.

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

Scott

comfychair
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http://75.65.123.78/driverhacks/Dsc07201.jpg

http://75.65.123.78/driverhacks/Dsc07202.jpg

7.52A from a 20R!

Tom E
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A parallel triple - that I understand. Because of the lower Vf per LED, you can achieve higher amps out of the cell with a FET based driver. Try it now with one XP-G2 and you will probably be somewhat disappointed, maybe 5.5-6A tops.

ImA4Wheelr
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I have a question for the electronics gurus.  Please excuse, but correct, any errors I have in the premise.

These n-channel FET's are basically variable current switches.  We are using PWM to control how much current they allow to pass from the cells to the LED's.  Voltage is not regulated like with an amc7135.  So we obviously only want to use this approach (assuming no buck regulation elsewhere in the driver) for situations were the LED's can take a direct connection to the cells (Made possible by copper and voltage sag).  This would seem to rule out 4AA Eneloops to one xml.

My question is.  In the case of one cell xml, or 2S mtg2, in the lower modes, are we subjecting the LED's to higher than Vf pulses (assuming less voltage sag) and, if yes, will this significantly shorten emitter life?

Tom E
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7135's limit amps, not regulate amps. I get the wording of this messed up too, but understand it now (I think I understand...). Sorry, can't help with the Vf pulse question.... Good question though!

PWM's are bad in the sense they cycle 100% of the amps, so the LED still gets full amps, but just for short bursts, so true multi-mode regulation (each mode is regulated) is more desireable, but probably more costly in parts, real estate, and driver design. We do have lights and drivers though that provide true "per mode" regulation, but you will find it in more pricey, bigger drivers and lights.

ImA4Wheelr
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I agree Tom, 7135's limit current, but they do regulate voltage as I said above.  If excess voltage exists above the Vf of the emitter, they convert it to heat.

comfychair
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7135s do limit current but they are linear regulators, not switching regulators. So when they are on, they are on, they do not adjust anything on the fly to maintain that fixed 350mA. So the difference in Vin and Vf has to be going somewhere, it isn't being dealt with by switching the output off briefly when Vout rises above Vf like a switching regulator would do. (this is also why there's no real benefit to using a 7805 regulator instead of a 'dumb' zener regulator - they both do exactly the same thing, the 7805 just has all the various linear regulator parts hidden inside so it can look like a smarter solution - a zener regulator is a linear regulator as well just using separate parts)

-----

I know these FETs won't do the same big numbers into a single LED, I already posted the numbers on that setup... but when this FET is removed from the circuit, there's very little increase in the current. It would only be 0.1A higher if you had a theoretically perfect 0.0000000000000 ohm Rds(on) FET that currently cannot exist in our universe. There is no FET that can give higher current from a single cell than what that cell will do when connected straight to the load without the FET in the circuit. It's just a relay with no moving parts. Lower on-state resistance will give higher current, and I have not found one yet in this package that is lower than this one's .0042 ohms at the voltages we're dealing with here.

Here's a list I've been building of some common FETs I've found on various drivers:

 

p/nmfgohms@4.5vmilliohms@4.5vnotes
DTU40N06dintek.013*13**@10v - 4.5v likely around 30mR
AO4468alpha.01818SRK 3-toroid driver, 3x FETs
PHD55N03-LTphilips.015*15**@5v
09N03Linfineon.01212.1 
2SK4212Anec.010410.4Securitying SRK clone, red 'JB' driver
50N03-07vishay.01010 
AOD436alpha.00989.8 
06N03Linfineon.00767.6 
05N03L (TO-263)infineon.00616.1 
SUD70N02-03Pvishay.00424.2http://www.ebay.com/itm/271319198579

Tom E
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Thanx comfy! Is the East-092 FET included in that list? Not sure if the #'s were sanded off, can't recall...

comfychair
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OnSemi T70N03 is 8.1mR, that's what was used on the 'good' ones. The one I use is half that.

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ImA4Wheelr wrote:

I have a question for the electronics gurus.  Please excuse, but correct, any errors I have in the premise.

These n-channel FET’s are basically variable current switches.  We are using PWM to control how much current they allow to pass from the cells to the LED’s.  Voltage is not regulated like with an amc7135.  So we obviously only want to use this approach (assuming no buck regulation elsewhere in the driver) for situations were the LED’s can take a direct connection to the cells (Made possible by copper and voltage sag).  This would seem to rule out 4AA Eneloops to one xml.

My question is.  In the case of one cell xml, or 2S mtg2, in the lower modes, are we subjecting the LED’s to higher than Vf pulses (assuming less voltage sag) and, if yes, will this significantly shorten emitter life?


That’s a interesting question ImA4Wheeler. :~ I would like to know the answer as well.
For any of the modes the current should be the same, we are just controlling how long a duration the on and off in a cycle is, using PWM. But I know when the load is removed from a cell the voltage starts to recovery rather quickly. So is it possible that in a low mode where the on time may only be 1% of a second, is that enough time for a cell to recovery a little voltage to produce a higher current when the on time rolls around again, especially since the on time was so short the cell didn’t have time to sag much to begin with. If the PWM is controlled at high frequency like 9khz, there so many cycles in a second I doubt the battery has enough time to recovery any voltage. I suppose that the battery see’s those load spikes so fast, it just see’s a very light load. I would think the battery doesn’t sag that much because the time it takes for the battery to adjust for the load suddenly its removed before it has time to sag down like it would in high mode. I’m not really sure exactly how the battery reacts to low modes, if it could actually produce higher current spikes in PWM. If tested with a oscilloscope, I suppose you could find out.
.
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Oscilloscope is a good idea.  I have one I got from a government surplus center, but I still haven't learned how to use it.  I bet I start putting these drivers in lights before I get around to it.  If an emitter fails, then I will definitely test.

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I’m reading it, grasping some of it, mispronouncing the Greek parts, and working on adapting it to fit my immediate need. Keeping my fingers crossed that some handiwork of a couple of good friends comes together…

Thanks Comfy for the explanations, the pictures, the inventiveness and wherewithal. Smile

And my S6! Wink

Edit: Oooh Oooh! Speaking of the S6, this would be awesome in it! I know I know you posted a pic of it happening, I got the same 7+A in my first triple XP-G2 from an AW IMR18350 in direct drive, which made me realize, control the overall output with the quality of the cell! A 20R or equivalent when absolute high power is needed. A Sanyo FJ from a lap pull when moderation is required, like for a loaner (a protected cell would be best there but you get the picture) Sweeeet!

led4power
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ImA4Wheelr wrote:

I have a question for the electronics gurus.  Please excuse, but correct, any errors I have in the premise.

These n-channel FET's are basically variable current switches.  We are using PWM to control how much current they allow to pass from the cells to the LED's.  Voltage is not regulated like with an amc7135.  So we obviously only want to use this approach (assuming no buck regulation elsewhere in the driver) for situations were the LED's can take a direct connection to the cells (Made possible by copper and voltage sag).  This would seem to rule out 4AA Eneloops to one xml.

My question is.  In the case of one cell xml, or 2S mtg2, in the lower modes, are we subjecting the LED's to higher than Vf pulses (assuming less voltage sag) and, if yes, will this significantly shorten emitter life?

The answer is:

In case of PWM based drivers, Vf on lower modes is the same as on highest mode,voltage sag is the same on all flashlight parts as on highest mode! That's big disadvantage of PWM based drivers.Check HKJs graphs for 7135 based drivers,on lower modes,current is constant until battery voltage drops to ~3.4V,same as on high mode,no matter what mode you choose.Voltage drops at springs,switch,wires remain the same on every mode.

In case of non PWM (true constant current regulated) driver,on lower modes current will remain constant until battery voltage become lower than Vf of LED at that current,for example 3.0V@300mA. Also there will be less stress on battery,springs,etc.

But,there is even something worse in case of PWM drivers. LED efficiency is the same on low modes as on highest mode!That could mean ~100lm/W for 3Amp max. driver,~80lm/W for 5Amp max. driver and ~70lm/W for driver with direct drive on high.

In case of non PWM driver,LED efficiency is much higher at lower modes,because  every LED is more efficient at lower currents.

In practice,that means for example ~150lm/W on medium mode,~200lm/W on low mode.That's 2-3 times better than for PWM drivers,so you could have 2-3X longer runtime on low mode,or 2-3x brighter low mode and the same runtime.

 

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Thanx led4power - that all seems to make sense, and certainly is the downside to these FET based driver designs. The quick answer of "that's why there's low modes" is not quite accurate (I use that explanation myself!). Tivo532's Z8 based designed driver uses FET's for a "turbo" mode, and 7135's for regulated lower modes, which is a better solution. For example you can get the "wow" FET based 5A-6A level, than also get PWM based modes on a much lower valued amp limit of 1.5A for example, so you get the efficiency of the Vf for 1.5A in lower modes, not the Vf of 5A-6A -- basically best of both without having a full blown PWM-less design.

DB Custom
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Um, Tom, didn’t he just say that 7135 based drivers keep the Vf at Hi levels even in low? So mixing the chips with the FET’s is not “the best of both worlds” but just more of the PWM world.

What driver is constant current regulated that allows the more efficient low modes? Anything in a 17mm? Anything that will deliver, say, 4.5A on High?

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There is no budget one cell driver with this functionality.

…mixing things up, a Pwm pulse delivers every time the full current:
On a nanjg 2.8A
On a FET maybe 6A
So if you would use a FET with 3 additional 7135, you would be able to use all modes below 1 A more efficient and still have the option to use the FET for higher modes.
——
I am unsure if the LED efficient a is the same in a current peak and on average current of the same high….I doubt that. I am also unsure if a XML can achieve 200lm/W…

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DBCstm wrote:
Um, Tom, didn't he just say that 7135 based drivers keep the Vf at Hi levels even in low? So mixing the chips with the FET's is not "the best of both worlds" but just more of the PWM world. What driver is constant current regulated that allows the more efficient low modes? Anything in a 17mm? Anything that will deliver, say, 4.5A on High?

Yes, it's PWM's, but PWM's off of 1.5A and not 6A -- big difference. Also I'm saying 6A as an example of what you would get with a FET (direct drive), while that 1.5A is based on how many 7135's you populate. His board has 4 spots for 7135's, so you could use one or could use 8 (4 stacked), etc.

I don't know of anything in 17mm size that does regulated multi-levels - you are right, therefore, PWM's off a lower high mode is the best I know of right now in a 17mm size, that's Tivo532's board - it's a compromise solution. His design is in the public also, so anyone can change or improve on it -- of course I don't have that capability. Some guys are adamently against the use of the Z8 MCU for example, but it could probably be designed with an Atmel MCU as well - same concept of FET or 7135 controlled output based on program control.

Another interested aspect of Tivo's design is the ability to run the FET's in parallel, with the advantage of reducing resistance with each one added. Again, you can stack FET's. Now if the Tiny13A FET designed here in this thread could support a stacked FET, would that cut the resistance in half as well? Interesting....

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I see how the 7135 chips in lower numbers would allow for a more efficient low, but how do they work together?
Not sure why I try. I’ll forget it all poste haste…

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DBCstm wrote:
Um, Tom, didn't he just say that 7135 based drivers keep the Vf at Hi levels even in low? So mixing the chips with the FET's is not "the best of both worlds" but just more of the PWM world. What driver is constant current regulated that allows the more efficient low modes? Anything in a 17mm? Anything that will deliver, say, 4.5A on High?

That is exactly what Tivo's East-092 build does, but his doesn't use the ATtiny13A chip, his uses an 8k flashable chip (he also has a 8*7135 driver as well)

http://budgetlightforum.com/node/25844

It's ALOT more complicated that an ATtiny13A chip and a decent enough FET, plus the 7135's can only handle so much current..

 

This is the final production thread

http://budgetlightforum.com/node/28558

 

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DBCstm wrote:
I see how the 7135 chips in lower numbers would allow for a more efficient low, but how do they work together? Not sure why I try. I'll forget it all poste haste...

What work together - the 7135's and FET's? You, from the firmware, control which output circuit you want to use - 7135 or FET's. It's two different circuits, throw a switch in the firmware (turbo ON or OFF), and the board operates as a FET output board, like comfy's here, or it operates like a regular Nanjg 7135 based board -- Best of Both Smile, or actually is both...

DB Custom
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Ahh, so if there’s a way to send it up in smoke I’d do it through my programming. I took programming in college. In 1980. Do you know how many times I’ve slept since then?

(Crimey but that makes me feel old! My wife was 4 when I was in college.)
[To clarify, she was 27 when we got married 11 years ago.]

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Great info guys.  Not sure if Comfy's approach will be harmful to the emitter still, but it's not going to stop me from implementing his approach on some of my lights.  It's a great solution for existing drivers that don't do what I want them to do.

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That is what the PWM function is for, control the overall power to the emitter, 4.2vdc won't instantly smoke a LED, but it will get HOT fast...if you didn't switch it off and on at varying levels then sure it more than likely would smoke...but this is why the PWM and lower modes come in...you can push the LED's at FULL BORE for a short time, then dial it back...the FET's just give you a HUGE pipe to push that current thru, the 7135's (that's why there is 8 gives you 8 little 1" waterhoses vs one big 8" main)

Not to insult your intelligence

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.22 LR gattling gun?

Sorry, your avatar…

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vs a 155....sure...heh

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DBCstm wrote:
Ahh, so if there's a way to send it up in smoke I'd do it through my programming. I took programming in college. In 1980. Do you know how many times I've slept since then? (Crimey but that makes me feel old! My wife was 4 when I was in college)

I started college in '75 in engineering, took a Fortran course and loved it. Eventually didn't finish my BS in EE, but went back for CS and got my first job in progamming in '78 at the age of 20. So, been working in software at every possible level for 35 years, more jobs/projects than I can recall. These MCU's are a throw-back to old times for me, but at least it's not assembly language...

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While I've been trying to figure these things out I did read a few things on some of the AVR boards about guys writing for the attiny13a in assembly to squeeze more functionality in...that was WAY over my head.  

Mountain Electronics : batteries, Noctigon, and much more! What's new? 

DB Custom
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Remember what they were saying back then, while the computer literally took up an entire room? “If the Automobile Industry were progressing at the rate of the Computer Industry a car would cost $20” Man, if they’d only known!
I dropped the programming when my Dad had cancer in ’83, got into the construction side of things and…well, became dumb.

He’s still free of cancer at 85 years old and I’m still dumb….

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Been through the IBM deck of cards for writing software on (don't drop the deck! your lines of code will get scrambled), the paper tape thing (yes, I can read binary on paper tape), 8" floppy disks, even bought the original IBM PC with the 4.77 Mhz 8088 (close to state-of-the-art at the time) for $3,500 with a monochrome monitor, single 5 1/4" floppy, DOS 1.0, etc....

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