"First Light" review of the Veleno Designs Quantum DD flashlight.

[Norm]

Got my light today.

Verdict: Severaly diappointed, light basically unusable.

Seriously. Yes, it is tiny and all. And thats all of it. The most important part is working less than shitty.

And with that I mean the actual function of the light, i.e. making light. There are like 20 turns of thread between head and body, most of them do nothing. Between onset of light and full power is maybe one rotation. Getting the light brighter than 10 lumens is difficult even when using both hands. When I finally got it tight enough to be relatively bright, it dented the bottom of the battery (which cannot be healthy).

The power ramping is EXTREMELY fragile, brightness jumps all over the place even when slowly rotating the barrel. After the first time getting it to maybe 30 lumens, the bottom of the cell was dented enough that the edges actually bypassed the QTC, making it a pretty bright direct drive light. Only that I needed a screwdriver jammed into the keyring port to get enough torque on it to be able to switch off again.

Tried the whole thing with the second battery I ordered, same game: Lots of force and dented bottom before I got it significantly higher than a quark mini on low. Without acutal force it went maybe to 5-10 lumen, and even getting there was no smooth sailing.

One handed operation is impossible.

I seriously consider right now to rip that stupid QTC out and replace it by a resistor to make an actually useable direct drive light with reasonable runtime.

It's always disappointing to read a post like this, your first approach should always be to the retailer you purchased the light from. Obviously you've read other positive reviews in this thread, having read those reviews the first thing I'd think is "my light is faulty" I'd then contact the retailer and give them a chance to make it right before posting a rant on a public forum.

Norm

 

[IMSabbel]

It's always disappointing to read a post like this, your first approach should always be to the retailer you purchased the light from. Obviously you've read other positive reviews in this thread, having read those reviews the first thing I'd think is "my light is faulty" I'd then contact the retailer and give them a chance to make it right before posting a rant on a public forum.

Norm

I did a complete doover for the light, degreased and regreased the threads and used another fresh battery, careful not to overtighten it at any point (which is deadly. As soon as the bottom of the battery is anything but perfectly flat, you get really strange behavior), and got it to run OK now, as long as I am careful when operating.

The main issue is that when trying to get bright, turning slowly (i.e. what normally would be considered "careful") is counterproductive: The torque needed is far to high without hooking the fingernail in the port for the keyring. Seems like the battery is sticking to the QTC or something.
Turing it on with oomph, i.e. directly as far as you want without slowing down, otoh, works ok (although it still is a bit dangerous in terms overtightening).

The main problem is that the way the QTC is used (i.e. just stuck at the bottom of the tube, in direct contact with the battery) is a bit of faulty design. Sandwitching it between two metal plates (with insulated edges) would have avoided most of the problems, and only made the light maybe 1mm thicker.

Just a question: is the QTC supposed to be magnetic? As it is astonishingly difficult to get a battery out of the tube again. Need to grab it with some needle pliers...

So as a final verdict, after getting over the initial diappointment (which was there, that was a heated post after I had to take an afternoon off to drive to the customs office as the parcel got stuck there), I am beginning to like the light. It has some difficulties, but on the other hand, size matters, and here the thing is just so rediculously tiny that it gets lost in the pant pockets.

 

[waywardgeek]

Disclaimer: I own no light this size, and have zero relevant experience with this class of device...

This category looks very cool, and the fit and finish looks excellent in pictures on this thread. I love the idea of a USB charger and shipping with the correct rechargeable battery. This is a clever use of a pressure sensitive resistor. I love that it's infinitely variable output, rather than having to rotate the head back and forth to select a brightness level that is unlikely to be exactly what I want at the time. I'm also a fan of TIR optics. Very cool stuff.

However, I'm wary of battery crushers. The engineer in me cringes at the power wasted in the resistor in medium and low light modes. The heat-sink designed into the tail is clearly aimed at cooling the variable resistor, rather than the electronics or LED. It's been suggested that power wasted in well designed power converter electronics is comparable to the power lost in a resistor, but this simply is not the case, even in low brightness modes. A fundamental limitation of any flashlight is it's reflector width. This light tapers down, limiting the size of the optics, making it harder to control the desired beam properties. The weight of this light without a battery is slightly higher than my Klarus MiX6, which takes a full AAA battery. Couldn't it be a bit lighter? The simplicity of this light's design is appealing, but there's wasted space in the head behind the optics, enough space to hold all the electronics. At this price, wouldn't it be better to build a non-crusher, slightly lighter and thinner, with better overall efficiency, reliability, and usability?

 

[KuKu427]

So let me get this straight...

1. The force needed to overcome the "stickiness" between a 4mm square piece of plastic and a smooth metal surface is too much for ones fingers...
2. 16 grams is too heavy to carry around...
3. The main purpose of the fins in the tail are used to cool the QTC and not hold tritium vials...
4. The tapering of the head limits optical cavity size and isn't used to provide more material to cut slots into the body with...
5. You can put a variable output driver into a cavity that's about... 0.5mmx10mm
6. Adding more components like electronics increases reliability...

:tinfoil::tinfoil::tinfoil::tinfoil::tinfoil:
Lot's of tin foil hats and experts around here these days...

 

[egrep]

At this price, wouldn't it be better to build a non-crusher, slightly lighter and thinner, with better overall efficiency, reliability, and usability?

 

[127.0.0.1]

Disclaimer: I own no light this size, and have zero relevant experience with this class of device...

This category looks very cool, and the fit and finish looks excellent in pictures on this thread. I love the idea of a USB charger and shipping with the correct rechargeable battery. This is a clever use of a pressure sensitive resistor. I love that it's infinitely variable output, rather than having to rotate the head back and forth to select a brightness level that is unlikely to be exactly what I want at the time. I'm also a fan of TIR optics. Very cool stuff.

However, I'm wary of battery crushers. The engineer in me cringes at the power wasted in the resistor in medium and low light modes. The heat-sink designed into the tail is clearly aimed at cooling the variable resistor, rather than the electronics or LED. It's been suggested that power wasted in well designed power converter electronics is comparable to the power lost in a resistor, but this simply is not the case, even in low brightness modes. A fundamental limitation of any flashlight is it's reflector width. This light tapers down, limiting the size of the optics, making it harder to control the desired beam properties. The weight of this light without a battery is slightly higher than my Klarus MiX6, which takes a full AAA battery. Couldn't it be a bit lighter? The simplicity of this light's design is appealing, but there's wasted space in the head behind the optics, enough space to hold all the electronics. At this price, wouldn't it be better to build a non-crusher, slightly lighter and thinner, with better overall efficiency, reliability, and usability?

LOL what ?

the fins are for looks, and to hold a trit...there is no heat in the QTC

[you need about a 1/2 million volts to heat up QTC to any degree]

power wasted in the resistor ? it is not a resistor, it is QTC material.
not the same as a resistor as far as how electrons are handled.

a lighter one ? you should have the Ti version

"Disclaimer: I own no light this size, and have zero relevant experience with this class of device..."

right, so all your comments and questions...I'll answer them (as an owner of 40DD, 44DD, and Quantum DD).
The light is awesome. Created from the mad popularity of the very expensive 38,40, and 44 DD series, the
Quantum DD is a more affordable version. The light is refined and well thought out already, years in the making,
and refined after hundreds of comments from owners. So...

and I have no problem operating the light with one hand, to any brightness. It is on my key ring, and the
key ring holds the butt whist I twist the head. No issues, just a little bit of finger training. At first it was weird,
and now it is second nature to grab it anytime anywhere and light it up at any level with one hand.

 

[127.0.0.1]

Just a question: is the QTC supposed to be magnetic? As it is astonishingly difficult to get a battery out of the tube again. Need to grab it with some needle pliers...

there is a magnet in the bottom that holds the QTC in place
the magnet also holds the battery in slightly

a firm tap into your palm will pop the battery out easily.
tweezers are needed to pull the QTC off the magnet

 

[AnAppleSnail]

It's been suggested that power wasted in well designed power converter electronics is comparable to the power lost in a resistor, but this simply is not the case, even in low brightness modes.

I agree with above remarks that finger-sized lights will never throw. Putting a 20mm optic on one requires entry into another size class. Let's talk power.

Assume 3.6Vbatt and reasonable Vfs for the LED. My experience is that even at 1-2 amps, QTCs do not heat up noticeably. I am not sure why. Some people tell me that it must somehow not have a voltage drop to dissipate heat, but I don't believe in magic. Let's calculate the heat dissipated assuming that it is a conventional variable resistor. Since it is sandwiched between two metal plates it can't heat significantly at a half watt for a few minutes' runtime.

Now. Why in the world are QTCs used in small lights?

1. Efficiency at low current, and operation at high current.

Current, Vf. (Vbatt-Vf)*current dissipated, (Vf*current used), (Pdissipated/Ptotal)% efficient.

1A, 3.15v Vf. (0.45W dissipated, 3.15W used, 87.5% efficient). This is a bit less than high-power, 1-cell driver circuits. I could do this trial with an XP-E and get better results through Vf matching, or use a lower-voltage Li-Ion chemistry for the same.
0.5A, 2.95v Vf. (0.325W dissipated, 1.475W used, 82% efficient). About what a cheap driver manages.
0.1A, 2.75v Vf. (0.085W dissipated, 0.275W used, 76% efficient). Not good performance for specialty low-performance drivers
0.01A, 2.5v Vf*. (0.011W dissipated, .025W used, 69% efficient). The 'overhead' of many drivers is 1 mA at 3.6v, or three times what is used here.
0.001A, 2.4 Vf*. (0.0012W dissipated, 0.0024W used, 67% efficient). I do not know of microcontrollers able to run at 400 microamps, nor many MOSFETs rated to 1A that run at this current.

This shows the operation range for the QTC. The efficiency levels out at about 67%, the ratio of the minimum expected Vf* of the LED and the nominal battery voltage.

*At very low currents, the Vf becomes extremely variable.


2. Size. Show me a microcontroller that can be mounted in this light to give a similarly convenient operation.

3. Cost.

4. Reliability. Yes, it fails. In that eventuality, remove or replace the QTC sticker and you get full functionality or a one-mode light. I can't do this with a conventional driver, even if I could build one to spec and size and cost!

 

[benthiccracker]

Trits on the battery capsule ? Why not...

Close up of trits

Did Precision works do the trit slots? Are these two different spare battery tubes, one with two slots in the bottom and the other with three?

 

[luceat lux vestra]

No beam shots?!!!!! What are you guys thinking? and does anyone have a one lumen run time number? This looks like a incredible little light!
I think I might need one.

 

[shao.fu.tzer]

No beam shots?!!!!! What are you guys thinking? and does anyone have a one lumen run time number? This looks like a incredible little light!
I think I might need one.

Just for you... No tripod or image stabilization, Quantum DD on fresh cell on second charge - compared with common Surefire P60 with new Surefire primaries. Beamshots taken at 12 and 40 feet.

First, 12 ft control:

P60 at 12 ft:

Quantum DD at 12 ft:

Control at 40 ft:

P60 at 40 ft:

DD at 40 ft:

Sorry again for the bad picture quality, but it's some form of reference...

 

[zebedee]

Thank you for the review :twothumbs, it made me order one. Now the wait for it to arrive

 

[kaichu dento]

This looks to be a great read, but first I just wanted to know, is that $20 hiding $1's or $100's?

 

[levi333]

Looks very interesting. I think I found my new keychain light.

 

[crizyal]

I have a first run 38 DD Ti with custom anodizing and trits. I have had this light on my person every single day since it arrived. It has made light like it was intended to without fail. It is the ultimate backup light (two is one, one is none)! I just purchased this Quantum DD for my wife. I am going to just slip it onto her keychain and see how long it takes her to find it. I love how there is very little to go wrong with this light. I am very appreciative that this style of custom lights has been made affordable to the masses. Thanks Steve and Craig for getting this developed and distributed.

 

[Coolz]

Thanks for this review, it helped me make the decision to purchase one! I really enjoy my Quantum DD. It doesn't get a whole lot of use quite yet, but it will soon, and I even ordered some yummy ice blue trits for it. I was curious as to what the expectations are when it comes to runtime for say, 25% to 50% brightness (1/2 a turn or so), a little more than firefly/moonlight mode would be. Surely it would be more than 16 minutes!?

Also, Steve, do you think you will be making a Ti version?

 

[Norm]

Also, Steve, do you think you will be making a Ti version?

There have been similar TI runs in the past, have a look at threads in the Marketplace, you might ask the question there.

Norm

 

[Coolz]

There have been similar TI runs in the past, have a look at threads in the Marketplace, you might ask the question there.

Will do, thanks.

 

[KarstGhost]

Here:

Thanks to this picture and the current price on this light I couldn't resist!

Has anybody used the 2nd version much yet? Thoughts?

 

[IMSabbel]

I finally dug this light out of a drawer again after I had forgotten about it for a couple months after my inital disappointment.

After some prodding, it seems that the 10440 cells are the single weak link. As soon as they are dented even a tiny bit, the QTJ will only get pressure at the corners, needing more pressure for the same resistance and increasing the problem.

I fixed a small 8x0.5mm supermagnet on the bottom of my cells with a tiny bit of epoxy in the hollow of the dent, and they work like a charm (as there is no way that the ceramic of the magnet would ever dent...)