Novatac -- Battery Consumption

In the coarse of performing some testing on my (2) Novatac EDC 120P lights, I discovered something which I thought was rather interesting. I don't ever recall seeing this type of erratic behavior in any of my past HDS lights. These run-times were done on (2) different Novatac lights, each powered by a brand-new SureFire CR123 cell. They were locked into the default secondary mode (30-lumens according to the manual) and left to run only until such time when output dropped significantly.

The 1st graph plots the data over the first 5-hours, the 2nd for 10-hours and the 3rd for 12-hours. Does anyone venture to guess what could be causing this erratic fluctuation? Visually, it does not appear to be noticeable that this condition is occurring.

Could it be pulsing? pwm

Well, the HDS runs with in part with PWM, and for sure your Novatac does. Looks like sine waves, very obvious sine waves.

Bill

Is there really that much difference in output between your 2 lights? also if it is pulsing it does not seem to be changing that much. you might not be able to see it with your eye.

I'm would imagine it's your light meter and not your lights, try throwing on a DD incan light, or even leave it under a house light for a few hours.

65535 said:

I'm would imagine it's your light meter and not your lights, try throwing on a DD incan light, or even leave it under a house light for a few hours.

Click to expand...

Trust me, it's not the light meter, but thanks for the suggestion.

this_is_nascar said:

Trust me, it's not the light meter, but thanks for the suggestion.

Click to expand...

Earthquake?

Seriously, obviously there are some regulation issue, maybe heat related

The one I returned did the same thing. You could detect it if using it for reading, but not for walking around.

I don't think its heat related. You would not see it that early in the test.

Not that it isn't related to the PWM function, but it's definitely not the actual PWM frequency, seeing as how there's a cycle about every 5 minutes in the graphs.

It looks like some sort of underdamped circuit that keeps overshooting it's set point or a feedback loop. I don't know a lot about complex light circuits but one idea is some sort of thermal feedback, not not necessarily overheat protection, but something warms up which initiates a reduction in power output. Light output decreases correspondingly and after a few minutes, temperatures come down which initiates an increase in power and thus light output and the cycle repeats. One thing that makes me think it might be thermal is how slow the oscillation is.

ULF (ultra low frequency) PWM - the newest wave in power saving
Seriously though txmatt may be on to something. I would have to say that if it is not visually noticeable then I wouldn't be concerned about it but I think it would be interesting to ask Novatac about it and also to run a test with some other batteries - different brands and especially with an RCR123 to see if there is any difference related to other battery types.

That happens in my 120P too. Especially when i have it tailstanding against a white wall, I can see it pulsating by about 1/4 to 1/2 lumens up and down at most settings between 10 and 60 or so. Except it does that every 30 sec or so.

I agree with the heat. this is the circuit correcting and re-correcting for tempature.
If you can't see the effect (I can't). It doesn't make one bit of difference.
What you are seeing is the circuit (heat protection) doing it's work.
Why not send the question to Novatac?

Yaesumofo

It's not heat, or at least not the desired and programmed method of heat regulation.

When the original hds or novatac overheats, it steps down 1 level. Even if cooled it will NOT step back up automatically. You have to turn the light off and on for it to step back up.

And really, it would have to be perfect conditions for it to be that steady. For as the battery discharges, current increases, and heat output increases.

I vote for a non-finished power supply and/or led regulation. Especially since 1) it seems to fit the data shown and 2) Henry said the light shipped, against his advice, before he was finished with the circuit.

And now that I look at the data again, something else becomes apparent. 2 samples of the same model light differ by 33%. Output is 6000 on one and 8000 on the other. This further goes to show that there are problems with the power supply, led control, or calibration.

could this have incidence on the flicker at lower levels?

but on another note, is no one willing to make a whole emitter module (emitter, circuit, slug) or whatever to swap into novatacs? would probably be an instant hit...

should have known better about novatac not taking henry´s advice about the non finished circuit before buying one

manoloco said:

should have known better about novatac not taking henry´s advice about the non finished circuit before buying one

Click to expand...

I'm still trying to get over that the 85P and the 120P have the same efficiency.


rob

manoloco said:

should have known better about novatac not taking henry´s advice about the non finished circuit before buying one

Click to expand...

Well, just to be fair, that is purely speculation, unless I've missed something. I EDC and use my NovaTac everyday and I've been completely satisfied with it's gorgeous beam, rugged build quality, and flexible UI.

txmatt said:

...it's definitely not the actual PWM frequency...
It looks like some sort of underdamped circuit that keeps overshooting it's set point or a feedback loop...One thing that makes me think it might be thermal is how slow the oscillation is.

Click to expand...

Likewise, that's my guess. Definitely not PWM, slow frequency indicates possible thermal. Also note the left side of the first graph -- it doesn't begin for a while.

However it might be the power/current regulation changing as the battery fades, but doing so in fairly large steps.

The fact both units behave similarly indicates it's not an individual malfunction, but expected behavior of the present design.

The variation is roughly 4-5% of output. I seriously doubt that's visible. Even a 40% variation (1 brightness step on an HDS) is only a small visible change.

Thanks for all the feedback everyone. I'll check closely again, but like I said, in normal useage I don't believe you can see this changing/pulsing of output. Here's the same data, plotted to show the first 60-minutes.



You can see that most of the peaks and valleys have a couple minute period of time where that output is stable.

Yes and they are very uniform also. it doesn't look random