Q3: 350mA or 700mA? AND Lux1 vs. Lux3 efficiency?

I've read on CPF that the Lux3 in the Q3 is being underdriven at around 350-400mA and thus can be driven harder and made brighter.
However, on Craig's site (ledmuseum), he measured the current draw to be 762mA.
Which is it?

If it's actually being driven at 700+mA as spec'd for a Lux3, why is the light output only equivalent to that of most Lux1 lights? Quickbeam's site shows it to be about the same light output as a Fenix L1/P, and just a bit more than a 2611X or a Longbow Micra, all Lux1s. The E1L also seems to be pretty low light output for a Lux3. I'm new and still getting used to all the binning stuff. Is it because these companies are using R-bin Lux3s and the others R-bin Lux1s?

If both Lux1 and Lux3 LEDs are the same bin (i.e. "R"), doesn't that mean that the Lux1 is considerably more efficient since it's able to produce the same amount of light at half the current? If so, what's the purpose of sub-"S" bin Lux3s since Lux1s are available up to "R"-bins?

IIRC, current to the LED can be different from current off the batt. This might explain the discrepancy. But, I'm not electronics guru, so I'll stop blabbering.

I'm no electronics expert myself but I will agree that my Q3 and Fenix L1P are about the same in light output. I also have my Q3 with the regular primary CR123 battery that it came with which is 3.0v i believe. I have read here on the boards that rechargeable CR123 batteries at 3.7v will make the light significantly brighter but have also heard that it may be over driving the 3w lux and could lower its life expectancy. So I'm curious to see my Q3 with a RCR123 (dont have any of these...yet) but at the same time i'm unsure if using them will ultimately ruin the light in the long haul. Its been stated somewhere also that the Q3 goes to direct drive when using a RCR123 but if its at the cost of deminishing lumen life, I would rather not use it. But then again.....by the time the light does lose its brightness, its time for a new and better one no?!

Keep in mind that with regulation or any type of circuit (vs a pure resistor) what you measure at the tailcap will ALWAYS be higher than what the star receives... That's part of the whole effeciency of circuit that so many guys have issues with. The Q3 is considered to have one of the least effecient circuits.

I've had a couple Q3s and have two Q1s that I've swapped Lux IIIs into. I run them on R123s so the different between a Q1 a Lux III and Q3 is pretty minimal.

Speaking of R123s. I think I measured my TW0J-modded Q3 in the low 900ma range on a fresh R123 cell which will drop as the cell drops below 4V and I measure in the high 900ma range on my Q1 with a TYAK star. This isn't significantly overdriving the Lux III. I think as long as you don't have an H bin star (which isn't likely), you'll still get LONG life out of the Q3 when using R123s.

On R123s, they are a good bit brighter, but I only see about 45 minutes of runtime based on my three examples.

As for measurements, I just took these in the last couple minutes... all are with completely topped off or fresh cells:

Nuwai Q1 w/TYAK Primary 0.36
Nuwai Q1 w/TYAK R123 0.98
Fenix L1P w/NiMH 0.76
Fenix L1 w/NiMH 0.62

The reason the LED might be overdriven in a Q3 with an R123 isn't because of average current to the LED, its because of the peak current to the LED. If you look at the current flow to the LED on an oscilloscope, you will see not a smooth current delivery, but a square wave pattern with a very sharp transient spike at the leading edge of each wave. At this point current flow is very much higher than the average current to th LED. So, if average current to the LED is at the high end of specs, transient current flow is much higher and could be significantly reducing LED life. Here is a screenshot from an oscilloscope on a Q1. Its a voltage tracing not a current trace. Due to the nature of voltage vs. current in an LED, the voltage spike is far less impressive than the current spike would be.

As for efficiency, the Lux1 and Lux3 do not inherently have differences in efficiency - in fact I think they may be the same animal but binned at different currents. This wasn't always the case. In the past the Lux1 used a less advanced phosphor deposition process but now the Lux1 uses the same process as the Lux3.

I don't think you'll find any Lux3 LEDs being sold today with less than an S bin, and they go as high as the U bin (rumors of V bin Lux3 samples abound but haven't been confirmed here). The Lux1 typically is a Q bin animal, but R bins are becoming typical and there are occasional S bins showing up.

If you drive an R bin Lux1 at 700 mA instead of its binning current of 350 mA, it would probably equal a T bin Lux3.

The Nuwai Q3 draws about 700mA for the original version -
there is a more recent version (distinguished by the "tactical" type switch with momentary ON) that has a newer circuit board, that has been reported to draw 1A(!)

However many people run the Q3 on rechargeable Li-Ion 3.6-3.7V RCR123

Please take a look at this thread

Nuwai Q3 with RCR123 + Nano Charger

Rechargeable Li-Ion RCR123 batteries are nomially 3.6-3.7V which is quite a bit higher than the regular non-rechargeable CR123A which are rated at 3.0V. When freshly charged RCR123 can measure as high as 4.2V!

The Nuwai Q3 (both versions) seem to by-pass the DC-DC step-up circuit when the Vin (ie: battery) exceeds the set Vout (in this case it's the Vf of the Luxeon) - so the Q3 in effect becomes direct-drive.

The current draw is in the region of about 740-800mA - at the rated 3.7V for the RCR123 - this close to about 3 watts - which is fine for the Q3 - since it is using a Luxeon III (3watt) LED.

BUT on a Luxeon I (1watt)
- the above power draw is probably too much for the LED -
as per the brief usage of a RCR123 in my S1801 1watt Luxeon (in the thread above) shows -
The S1801 1watt with RCR123 was very bright, and became very warm very quickly -
drawing about 740mA which is close to 3watts.......

So unless a 1watt Lux light has some other means of regulation/protection -
I would suggest it is probably not a good idea to use a 3.6-37V rechargeable Li-Ion RCR123 in it.

Thanks for the info guys. It still doesn't seem definitive to me whether the Q3 is driven at 350mA or 700mA. Cratz2's measurements on primaries at the tailcap would seem to indicate the 350mA range, but Craig's (LED Museum) measurements indicate 700mA range.

wasBlinded: thanks for the scope output. It seems the circuit in the Q3 does no filtering of the signal and just sends the actual signal thru at a frequency that the human eye can't see (in contrast to drivers that will take a PWM signal to control it's output, but the output is DC). Thanks for the info on the Lux1 and Lux3 bins...to me, if an equal flux-binned Lux1 and Lux3 can create the same light output, but the Lux1 uses half the current, it's more efficient. However, it seems Lux1s aren't readily available (except for processing anomalies - the rare S-bins) in anything higher than an R-bin, while Lux3s start at S-bin, so that makes sense now.

jsr wrote: "It still doesn't seem definitive to me whether the Q3 is driven at 350mA or 700mA. Cratz2's measurements on primaries at the tailcap would seem to indicate the 350mA range, but Craig's (LED Museum) measurements indicate 700mA range."

Scott/milkyspit does a lot of Nuwai Q3 upgrades so he probably can be pretty definitive about the current draw and any variations.......

To answer your question on battery vs emitter current it is imperative to know how a light is driven.

In some cases, the emitter is driven directly off the battery, through a resistor or through a PWM'd (pulse width modulated) switch. In these cases, the emitter currect and battery current should be the same as it is a series-connected circuit and the current flows in a loop.

A reasonable measurement of the current in the first two cases can usually be done with a DMM (Digital MultiMeter) on the highest current setting (often 10A). Why the 10A setting when measuring only a fraction of an amp? Because the 10A setting will introduce the least resistance to the circuit under test and therefore have a smaller impact on the operating parameters of the circuit. In essence, there is a slight voltage drop across the point where you insert the DMM in series with the circuit when measuring current - this voltage drop results in less voltage getting to the circuit and can result in a higher (or lower) reading than if the DMM were not in the circuit.

For the PWM direct-driven circuits (such and Lion cub/heart, POP, FLuPIC), you would want to measure the averaged current. Unfortunately for measurement purposes, many TrueRMS DMMs do not measure accurately at the switching frequencies used in these drivers.

That covers the direct-driven type lights. The other type of lights use switcher-type drivers where electrical energy is converted to another form (magnetic field in a tiny coil or energy stored in capacitors for charge pump circuits) and then back to electrical energy at a higher/lower (boost/buck) voltage. (There are many flavours of converters out there.) This energy conversion comes at a cost (converter losses). Converter losses are usually presented as converter efficiency. The efficiency figure should be presented as a range because, the efficiency will vary over the input and output range of the converter.

To sum this up in an equation:

Power Out = Power In - Efficiency Losses

Power = Voltage x Current

Note that for a given power level, if you change either the voltage or the current, the other must go up or down to deliver the same power. So, to put that into real terms, if you have a fully regulated driver such as a NexGen that puts out a constant current, the current draw from the battery will go up as the battery voltage drops until the driver can no longer remain in regulation.

For example:
Let's take an non-existant lossless regulated driver (efficiency = 100%).
Let's assume it drives a LuxIII at 800mA and the Vf at this current is 3.8 volts.
Power to the emitter is: P=V*I = 3.04Watts
Let's power this with a primary Lithum CR123A. The battery will be under load so the voltage will sag. Let's say it sags to 2.8 Volts under this 3.04Watt load (remember that we have a 100% efficient converter).
3.04 Watts (P) = 2.8V (V) * (I)
I = 1.086 Amps
So in this case, the battery current would need to be 1.086 Amps to produce 0.8 Amps at the higher emitter voltage.
When the battery becomes depleted, the voltage will drop even more and teh current will have to continue to rise to keep the driver in regulation. Eventually, the battery will not be able to supply enough power and the driver will fall out of regulation.

Now, let's look at the effect of converter efficiency. If, in the example just given, the converter efficiency was 75%, the battery would have to supply 3.04/0.75 = 3.58 Watts to get 4.05 Watts to the emitter.
Let's assume the same battery sag (2.8V). 3.58/2.8 = 1.44 Amps! Compare that to the ideal driver above.

Note that the Q3 has a switching regulator. So battery current is not emitter current.

This simple example covered one type of driver. There are many other types including some that combine PWM and current regulation. There are also different flavours of Q3s with slightly different circuitry. The Vf of the emitter in the Q3 also affects the drive current. Running the Q3 with the stock driver circuit more or less results in a direct-driven situation while the battery voltage is greater than the emitter forward voltage. There may still be some losses through the driver.

This is certainly not and exhaustive explaination. There are lots of posts regarding converter efficiencies and taking accurate measurements. Happy reading.

Paul

didnt nuwai make some changes on the Q3?

-David

Yes Nuwai changed driver boards. I have one of each. You can also read more here.

Paul

jsr said:

Thanks for the info guys. It still doesn't seem definitive to me whether the Q3 is driven at 350mA or 700mA. Cratz2's measurements on primaries at the tailcap would seem to indicate the 350mA range, but Craig's (LED Museum) measurements indicate 700mA range.

Click to expand...

Please note that the numbers I just posted above are for a Lux III in a Q1 host with the stock Q1 circuit. I believe the Q1 and Q3 circuits are simple voltage boosts and allow the 3.7-4.2 volts from an R123 to simply pass through leaving the light to act as a direct drive. On a primary 123, the Q1 with the Lux III is a bit dimmer than a Q3 with a T-bin star.