Viability of QTC -- is it "over" or is there still some way to make it work reliably?

xevious

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Viability of QTC -- is it "over" or is there still some way to make it work reliably?

QTC (Quantum Tunneling Composite) seemed like a phenomenal "free lunch" opportunity to achieve a ramping brightness control of a flashlight without the complexity of circuitry. PEAK LED Solutions jumped into using QTC quite a bit, but from all I've been reading it hasn't worked out all that well. All kinds of reliability issues. I had seen some DIY QTC flashlight topics from back around 2011, but they went nowhere...

So what's the upshot on QTC for flashlight use? Was there a "roadblock" reached whereby it was deemed as not a practical device for use in flashlights? I had wondered if there might be some inescapable wear factor... the frequent compressing and decompressing of the QTC material can cause deformation, and perhaps degradation. Is there some other consideration that makes it nonviable? Or is there the potential for a different sort of design that might be able to leverage QTC effectively and reliably for longer periods?
 
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archimedes

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Pure compression and decompression is not really the issue, it is that shear forces cause "crumbling" of the substrate sooner or later. Those crumbs then really magnify the jitteriness and "noise" of the resulting output.

Yes, Peak improved their QTC design in succeeding versions, but as a relatively simple electrical "pill" it remains limited in smoothness of response.

There was at least one much more sophisticated (and costly) design modded here on CPF, but I don't recall it progressing to completion and full production, beyond prototypes.

The concept is sound and I think it is a valuable technology, but QTC has been largely dropped, due to lack of both market demand and hobbyist interest :shrug:
 

fyrstormer

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

I always wondered why nobody tried using the "guts" of a simple carbon-film potentiometer to make a rotary adjustable brightness control, that could be adjusted by turning the head or tail of the flashlight. It wouldn't require compressing anything, so there wouldn't be any thread wear to worry about, and it wouldn't involve any rubber parts that will inevitably oxidize and fail over time.
 

LRJ88

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

My Peak flashlights are working perfectly and dial in to whichever level i want reliably, but i've had them for years now and chances are they're just worn in so well that they don't wiggle out of position etc. too much.
 

fyrstormer

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Alternately you are being more careful when adjusting them than most people are -- not necessarily consciously, but as a matter of habit.

I have a couple QTC Peaks. They're okay, but the lowest settings are incredibly difficult to reach reliably -- it's way too easy to overshoot. I removed the QTC material from one of them and soldered the two halves of the pill together and reinstalled it, using it as a single-mode light. It's much more predictable that way.
 

xevious

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archimedes

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Thanks for your replies, archimedes. :twothumbs I think I have a good understanding of it now. Maybe one day if some other composition can be developed that will resist the shearing forces and crumbling, it could actually work.

You are welcome. It is a very interesting technology, for sure, but does have its quirks.
 

id30209

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Dang...just read this thread as i got my TheFraz 3rd run...
I like this simplicity, over numerous mods and offers these days.
At the end of the day i just need something simple as QTC. The only thing is bothers me is aluminium housing which is gauged by QTC so brightness transition isn't smooth anymore. At least pill is still OK so at this time i need to find some thin and hard washer to use over Al body contact lip.
 

xevious

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

I always wondered why nobody tried using the "guts" of a simple carbon-film potentiometer to make a rotary adjustable brightness control, that could be adjusted by turning the head or tail of the flashlight. It wouldn't require compressing anything, so there wouldn't be any thread wear to worry about, and it wouldn't involve any rubber parts that will inevitably oxidize and fail over time.
Sounds interesting -- the current designs aren't as concerned about miniaturization, but I wonder if a different design could be achieved that would be workable in a flashlight.
 

Hoop

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Very fine threads should help with the brightness accuracy. The mechanism can also be designed to transition into true direct drive at maximum crush level. I've designed and modeled a 10mm qtc non-battery-crush pill in 2016. NBC QTC pills can be made very small.

It has been done more times than I had previously thought, as pointed out to me by Calvin at IS: Veleno Quantum, Jetbeam Mini-1, Cooyoo Quantum, Mecarmy Illuminex, Maratac Peanut, and more.
 
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fyrstormer

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

The Jetbeam Mini-1 uses a metal "bottle cap" switch (I don't know the correct name) that provides two stages of brightness: The low stage engages when the metal "bottle cap" switch comes in contact with a brass pin connected to the positive battery terminal, and the high stage engages when that brass pin pushes the "bottle cap" switch against a contact directly beneath it on the driver board. It's basically a different version of the same two-stage switching mechanism used by the Muyshondt Aeon/Nautilus and the McGizmo PD lights.

The problem with threaded compression switches like Peak's QTC, where you have to pinch the hell out of a little chunk of semi-conductive rubber to get full brightness, is not so much making adjustments when increasing the brightness, but when decreasing the brightness. In that case you're fighting friction between two sets of tightly-meshing threads, and that makes it extremely difficult to avoid overshooting the brightness you want. (yes, even with proper lubrication on the threads; I own a couple.) I've gotten the best results from my Eiger Ultra, because the head is much wider than the threads, so my hand has more leverage to make very fine adjustments when loosening the head to lower the brightness. But it's still less precise than, for example, the control rings on my Jetbeams, which don't build up any compressive force at all when making adjustments.
 
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wosser

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

How about using a load cell instead of fancy materials? The circuitry may be a bit more complex but the principles of operation and environmental susceptibilities are well understood.

You can even tune a load cell in either hardware (more or less metal in shear/bend) or software (ADC limit / average, temperature compensation).
 

TheFraz

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Dang...just read this thread as i got my TheFraz 3rd run...
I like this simplicity, over numerous mods and offers these days.
At the end of the day i just need something simple as QTC. The only thing is bothers me is aluminium housing which is gauged by QTC so brightness transition isn't smooth anymore. At least pill is still OK so at this time i need to find some thin and hard washer to use over Al body contact lip.

The flicker that comes with qtc degrading and other imperfections related to the pressures in a twisty type switch were one of the main things that needed to be addressed. That and the material itself. I've been R-and-D-ing for a couple years since the last model released - I feel confident these issues are addressed.

-Fraz
 

id30209

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

The flicker that comes with qtc degrading and other imperfections related to the pressures in a twisty type switch were one of the main things that needed to be addressed. That and the material itself. I've been R-and-D-ing for a couple years since the last model released - I feel confident these issues are addressed.

-Fraz

Wow! The Fraz is here[emoji1690]
Are we about to see new improved design?


Sent from Tapatalk
 

TheFraz

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Wow! The Fraz is here[emoji1690]
Are we about to see new improved design?


Sent from Tapatalk

Absolutely! :grin2:
Good to be back. New engine design that will accept easily user-replaceable smart materials (of the QTC nature). I will update the original thread soon and make a new thread of the new models. All manufacturing is done in-house now, so it will be small batch at first. Four new models currently in operation - 18650, and 3 26350 models (weird, I know). Including what I think is the current shortest nasty thrower (uses a 26350).

-Fraz
PhPvt3W


Fnxf8VN
 

id30209

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Re: Viability of QTC -- is it "over" or is there still some way to make it work relia

Great design and biggest update in this thread!
Didn't expect this is going to be in the final stage TBH therefore it makes even more interesting!
IN for each!!!


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