# Anyone try the Lightsaver Miser for SureFire?



## wrathothebunny (Jul 4, 2007)

It allows variable levels of output (100%, 75%, 50%, 25%) via a PWM (Pulse Width Modulated) regulator circuit on any SureFire 6P/9P/C2/C3/Etc. & E2E/E2D - while keeping full color temp. The questions I have are - Is it reliable? How is build quality? Do the oscillating pulses damage the Xenon bulb filament? Do the output levels perform as advertised? How is the UI? What are your overall impressions? Here's the link to the product.

http://www.wargear.info/products/lightsaver-miser-multi-function-tail-cap-upgrade.html


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## 021411 (Jul 4, 2007)

Never heard of this until now. It looks pretty nice. Multi-levels would be nice to have. Until proven otherwise I wouldn't carry it on my EDC. Maybe for around the house type stuff...


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## DM51 (Jul 4, 2007)

With an incan you shouldn't get any flicker, but I don't see how it can keep the color temp up.


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## wrathothebunny (Jul 4, 2007)

DM51 said:


> With an incan you shouldn't get any flicker, but I don't see how it can keep the color temp up.



Pulse Width Modulation keeps the color temp up by cycling between full voltage and no voltage very rapidly, so the filament is never undervolted, thus maintaining the high color temp.


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## DM51 (Jul 4, 2007)

wrathothebunny said:


> Pulse Width Modulation keeps the color temp up by cycling between full voltage and no voltage very rapidly, so the filament is never undervolted, thus maintaining the high color temp.


I know the principle, but does this work in practice? An incan doesn't go instant-on like a LED, so the square wave must get rounded off and end up looking like a sine wave, or even nearly flat. It isn't like an A2's regulation, where the voltage is kept to a constant optimum figure - with this thing you are dragging it down to 50% or 25% etc. I just don't see how the color temp doesn't suffer.


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## wrathothebunny (Jul 4, 2007)

I expect that the voltage waveform would look rather flat. In fact, instead of a sine wave, there might be a voltage surge at the very beginning that quickly levels out to a flat waveform.


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## DM51 (Jul 4, 2007)

Roughly what I thought - so wouldn't it flatten out at much lower than the bulb's optimum voltage?


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## wrathothebunny (Jul 4, 2007)

I see no reason why it would operate below the bulb's optimum voltage. The only thing that would cause voltage to sag substantially would be excessive current. The only thing that would cause excessive current would be a decrease in resistance along the filament (assuming constant internal resistance for the cells). The only thing that would cause a decrease in resistance along the filament would be a cooler temperature. So, basically, the filament would have to cool enough between each cycle to actually lower resistance to the point that it would be drawing excess amps from the cells. I don't really see this happening, especially if running on Li-ions. If the filament provides roughly constant resistance, then I am sure that the switching mechanism can supply a pretty flat oscillating voltage square waveform - where the peaks reach full voltage as provided by the cells, and the valleys reach near or complete zero. You would basically have a strobe that is flashing so fast that it looks like one continuous beam, just like TV and Movies have frames that cycle so fast it looks like smooth motion rather.


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## 021411 (Jul 4, 2007)

Here's the solution. Buy it and test it out for all to see. :naughty:


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## DM51 (Jul 4, 2007)

I see exactly what you mean, but the whole idea seems counter-intuitive. You have an optimum voltage and a zero voltage. At the 50% setting, it is going to be half the time on optimum and half the time on zero. It doesn't seem logical to me that the apparent average, or the peak of whatever the voltage wave profile looks like (maybe pretty flat) ends up being the same as optimum. It would be just as logical to suggest the apparent average voltage should be zero. That's the problem I have with it - it seems to me the average voltage should be just that - average (ie half optimum). Ergo, yellow bulb. 

Maybe there's a major flaw somewhere in my reasoning, but if you cut the power half the time to a relatively large, slow-reacting thing like an incan filament, I don't see how you can expect anything other than an averaged-out response.


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## wrathothebunny (Jul 4, 2007)

I don't think filaments are as slow reacting as you think they are. Take flashes for your camera for instance. You can sync those to 1/500th of a second. I know all this sounds counterintuitive, but such is the nature of square waveforms. In terms of overall signal strength, sure, you average the output. Thus a 50% peak & 50% valley square waveform produce a light as half as bright to our eyes. But in terms of the interaction with the filament, it will only see full voltage, and no voltage - it will not experience "average" voltage for more than a miniscule instant compared to the valleys and peaks. Anyway, on 2 18500s running a P90, it would look like this. 

XXXXXXXXXXXXXX 7.6 V
XXXXXXXXXXXXXX
XXXXXXXXXXXXXX
XXXXXXXXXXXXXX
XXXXXXXXXXXXXX 0.0 V

The peaks will push the filament to full bright, the valleys might still allow some glow to linger, but no voltage=no current=no electromagnetic radiation emitting from the filament except due to residual heat.


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## KeyGrip (Jul 4, 2007)

I might pick one of those up once my LF lamps arrive. I can't give very in depth reviews, but I can take basic beamshots, and I know a guy with an A2 to use for comparison.


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## leukos (Jul 4, 2007)

I would be interested in reviews, but it looks like it is the same IQ switch for minimag lights but in aluminum housing for SF lights. The IQ switch was met with mediocre reviews here at CPF.


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## carrot (Jul 5, 2007)

This product sounds pretty wicked cool to me. The A2 is proof of PWM working perfectly for brightness and tint control... the circuitry inside, Willie Hunt's LVR, uses it to ensure a bright white light. So I'm willing to believe their claims.


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## DM51 (Jul 5, 2007)

I think 021411 has the safest solution - test it and see. It's a bit like global warming - the claims may be true, but I'm not convinced yet.


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## nerdgineer (Jul 5, 2007)

wrathothebunny said:


> I don't think filaments are as slow reacting as you think they are. Take flashes for your camera for instance. You can sync those to 1/500th of a second. I know all this sounds counterintuitive, but such is the nature of square waveforms....



I think you might be mixing technologies here. A camera flash is a high voltage discharge through a noble gas with no filament involved. It IS fast. An incandescent is current heating a wire filament, where the halogen gas just helps reduce vaporization of the filament metal, and it is much slower (a typical household incandescent bulb evens out 60 Hz AC into about flat, it responds to 127 V pk-to-ground AC just like it would to 110 V or so (I forget the actual numbers) DC. 




wrathothebunny said:


> ...In terms of overall signal strength, sure, you average the output. Thus a 50% peak & 50% valley square waveform produce a light as half as bright to our eyes. But in terms of the interaction with the filament, it will only see full voltage, and no voltage - it will not experience "average" voltage for more than a miniscule instant compared to the valleys and peaks...


The filament will keep glowing as it cools and so puts out light at a reduced color temperature even when the voltage is off. Also, it takes a while for the filament to reach steady state temperature, so it won't heat all the way to full temperature when the voltage is on for a fast enough pulse repetition frequency (~ 60 Hz or faster for a household type incan bulb).

The net result is that the _*temperature profile*_ of the filament (which is what makes the incan light) under PWM WILL smooth out the voltage ripples and act just like it would under a DC voltage of lower value - hence you would get lower color temperature. 

It's either that, or you get a real slow PWM which you will be able to see and be annoyed by, or you will have to have some exotic incan filament with a very fast temperature rise (on the order of a millisecond) for this to work. Such a filament would be very thin and probably have a very short lifetime. Maybe incan flashlight filaments actually have millisecond temperature rise times, I don't know; but if not, there's no way around this.


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## DM51 (Jul 8, 2007)

A response from the bunny?


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## chumley (Jul 8, 2007)

I have 2 Black Diamond headlamps that have pwm dimming and the light color gets more yellow with the dimming, just like any incan that isn't getting full voltage. I didn't see any claim on the link that it would maintain full output color temp while dimming.


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## senna94 (Jul 14, 2007)

I am really surprised no one has ordered one of these yet. I am tempted to get one and find out if it really does all it says. I haven't dealt with this company before, but it seems they want you to be happy with your purchase.


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## Art Vandelay (Jul 14, 2007)

If it will let a G2, 6P, or E2E tailstand it's worth the price, even if the PWM does not work.


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## LuxLuthor (Jul 14, 2007)

DM51 said:


> A response from the bunny?



I'm going to have nightmares tonight.


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## KeyGrip (Jul 14, 2007)

senna94 said:


> I am really surprised no one has ordered one of these yet.



I'm planning on picking one up after I get back from Ireland. Until then, all my money must be saved. :mecry:


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## LightToad (Jul 15, 2007)

Just received the E2E version this week. It seems well made but it does turn progressively more yellow at each reduction. Still useful and you don't have to cycle through each time to turn it off. After you settle on a setting for a few seconds the next click shuts it down.


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## DM51 (Jul 15, 2007)

LightToad said:


> Just received the E2E version this week. It seems well made but *it does turn progressively more yellow at each reduction*. Still useful and you don't have to cycle through each time to turn it off. After you settle on a setting for a few seconds the next click shuts it down.


In other words, the color temperature goes down. Despite all that talk about PWM being able to work for incans just as it does for LEDs, with no loss of color temperature, you might just as well not bother - all this thing does is effectively lower the voltage.


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## leukos (Jul 15, 2007)

I'm assuming this is designed for the input voltage from two CR123a and wouldn't accept variable voltages. I wouldn't have much use for it.


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## wrathothebunny (Jul 18, 2007)

nerdgineer said:


> The net result is that the _*temperature profile*_ of the filament (which is what makes the incan light) under PWM WILL smooth out the voltage ripples and act just like it would under a DC voltage of lower value - hence you would get lower color temperature.
> 
> It's either that, or you get a real slow PWM which you will be able to see and be annoyed by, or you will have to have some exotic incan filament with a very fast temperature rise (on the order of a millisecond) for this to work. Such a filament would be very thin and probably have a very short lifetime. Maybe incan flashlight filaments actually have millisecond temperature rise times, I don't know; but if not, there's no way around this.



Sorry, I've been on vacation for the past 2 weeks. Anyway, I don't know that it is a foregone conclusion that human optical processing averages varying levels of color temp like you describe. The higher color temp would be emitting max lumens during the peak voltage of the waveform, and the lower color temp emitted during the valleys would be at lower lumens.

In any case, LightToad's experience with warming does seem to confirm the difficulty implementing a pulse-width-modulating setup with incans. However, this difference may reflect what you were discussing before, concerning the length of time needed for incandescent filaments to respond to voltage input rather than how the human optical system averages oscillating color temp values. It may be possible that the filament never reaches max burn on the lower settings, or perhaps the PWM circuit is poorly made.


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## Dinan (Aug 8, 2007)

This tailcap looks good on paper... but it would kinda stink if it only worked for 6V setups. Also, doesn't strobing an incan lamp reduce the life of it significantly?

EDIT: I did find this though - 



> • Functions with 6 to 12 Volt lights - 2, 3 and 4 cells



Not sure if that means it only works with 6, 9 and 12 discretely or if it works with 7.2/7.4V rechargeable setups... I'm not an electrical engineer =)


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