Alright, after BestOfferBuy dropped the ball on getting me an E07, I was able to find another one for not too terrible a markup. Combined with the QTC that Don sent me - $20, infinitely variable flashlight in an AA form factor. Seriously awesome.

I'll have more info in a bit.

What is QTC?

Quantum tunneling composite

Great ! Can't wait to see how you resolve it...

The first Quantum Flashlight?

ooo, I am interested in this! Maybe one of my 3 E07's could get this treatment :) I do love the little lights, so improving on them would be amazing!

Alright - take 2! Better quality, now with sound!


I don't understand at all.

This light isn't infinitely variable out the box.

Where is the more info?

My little and new understanding from a brief read of that wiki link is that QTC is resistance based.. so the light will be demanding a chunk of power from the cell even when the brightness is minimal?

The information is this (sorry, no good camera where I am to demonstrate):

There's a small piece of QTC glued in to the head of the flashlight in the positive connection terminal. As I twist the base and engage the plunger mechanism, the QTC is compressed and more and more current flows through the now-connected circuit, feeding the LED greater and greater current.

The thing to remember is that batteries do not push current, the LED pulls it. At minimal brightness, there will be minimal current draw.

and where can one acquire this QTC that you speak of?? :)

You can call it a QCT or anthing else you want but it's still just a fancy variable resistor.

Resistors can only drop voltage one way - by converting electical potential into heat.

So you're still draining the battery like mad when you choose a low light output. But at least your hand stays warm.

It's far better to stick with dc-dc converters for their energy efficiency, and forget dropping resistors.


uhm.... Sorta. The Fv of the LED drops with current rather slowly, so the LED is actually drawing very little current at a slightly lower voltage. Yes, the QTC is dissapating some energy, but its quite trivial.

Any pics of that QTC? Also, where do you get them?

I never considered that the battery squasher design of the E07 could be a benefit. I have to try this with mine.

There's not really much to show - it's essentially a dark grey/black 4mm square of squishy rubber material. I got a couple of spares from Don here on the forums.

So where do I send my E07 so you can make it just like yours? :bigsmile:

Or I could send you a few pills of the stuff to play with. It is cheap but there is a rather large minimum order of the stuff so I had to buy about 70 of the pills. From memory the pills are around 35 cents each and they weigh next to nothing so postage will be cheap.

While it isn't 100% efficient, it is operating more or less as a tap here, passing only so much current depending on how squished it is. When it is unsquished it has a very high resistance and as you compress it the resistance falls.

I doubt it'd work well in high power applications, the heat has to be dissipated inside a 4x4x2mm chunk of rubbery stuff.


But they have a rather large minimum order.

What do you use to glue the QTC in place?

Awesome mod, Jekostas!

Don, if you have a few extra, I'd love to buy a few off of you. I've been wanting to experiment with that stuff for awhile now, but have had too many irons in the fire lately.