I wonder why mfgrs like mag use it. Energizer on their lithium lite i saw at target advertized using it saying it adds to efficiency. My quark AA does not use it. PMW wreaks havoc on a camera when im trying to film under it 
PMW.... WHY???
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Maybe they use it since many microcontrollers have built in PWM outputs. Then its simply two parts, the micro and a FET to control brightness. Now why they select a frequency that is so low I'm not sure why. Its very easy to run a PWM at 30kHz and higher where it is out of the range of hearing.
no, the quark does NOT us pwm on any level
bshanahan14rulz
Flashlight Enthusiast
Yeah, I understand the why, I don't understand the choice of a low frequency PWM.... it's very annoying. Probalby has something to do with keeping the external components count down or keeping the supporting components' size down.
Swedpat
Flashlight Enthusiast
I guess it's a misunderstanding here concerning PWM of Quark. Regular and tactical Quarks don't use PWM but the Quark Minis do.
AnAppleSnail
Flashlight Enthusiast
And the full-Quark's digital regulation circuit modifies its output a certain number of times per second - at extremely low levels in some individual lights this creates a bright/dim cycle that looks like PWM.
HKJ
Flashaholic
I wonder why mfgrs like mag use it. Energizer on their lithium lite i saw at target advertized using it saying it adds to efficiency. My quark AA does not use it. PMW wreaks havoc on a camera when im trying to film under it
There are some very good reason to use it. One of the reasons are that without pwm it would not be possible to dim LiIon light that only uses a boost converter.
Another reason is cost, it is nearly free to implement pwm, when using a microcontroller.
With the camera you just have to select a slow shutter speed to get around the pwm, 1/100 second will usual work.
Wiggle
Flashlight Enthusiast
I don't mind PWM at all. It never shows up in any of my normal uses. Its true that it's less efficient but it also seems less likely to tint shift a light at lower drive levels which is nice.
Sub_Umbra
Flashlight Enthusiast
Bingo. It's also a great way to fine tune the tint on 'white' LEDs for those among us who are sensitive about that. (Not ne but there are quite a few tint sensitive folk out there)
PWM is also the only game in town for varying the output of monochromatic lights without drastically shifting the color. CYAN LEDs are a good example for this. I have a Rigel MIL Starlight Mini, which has widely adjustable output. It's a great light but it drops rapidly towards green on any setting but max, where it is CYAN. OTOH the Photon Freedom NV Green (CYAN) with PWM ramps down throughout it's entire output range with very little change in color.
when i use it as a video light it goes crazy. I use it (XL100) as a lighting aid in some of my videos i put on youtube..
Ray_of_Light
Flashlight Enthusiast
PWM is usually a power miser. PWM controllers usually necessitate a very low drive current, to overcome the Gate-Source capacitance of the power MOSFET.
Higher is the pulse frequency, higher has to be the drive current. This phenomena is well known to computer chip makers, where the clock frequency is routinely lowered to decrease the current consumption.
PWM was a very spread design technique for motors and incandescent lamp, which both had respectively high mechanical and high thermal inertia to make inconsequential the use of pulsed currents.
For LEDs, PWM is used to keep the driver component count low. Low frequency PWM is used in case of ultra-low power bootstrapped controllers (see the Olight M30).
In terms of electrical efficiency and luminous rendering, in the case of LEDs, PWM is a very objectionable choice.
Anthony
Higher is the pulse frequency, higher has to be the drive current. This phenomena is well known to computer chip makers, where the clock frequency is routinely lowered to decrease the current consumption.
PWM was a very spread design technique for motors and incandescent lamp, which both had respectively high mechanical and high thermal inertia to make inconsequential the use of pulsed currents.
For LEDs, PWM is used to keep the driver component count low. Low frequency PWM is used in case of ultra-low power bootstrapped controllers (see the Olight M30).
In terms of electrical efficiency and luminous rendering, in the case of LEDs, PWM is a very objectionable choice.
Anthony
shipwreck
Enlightened
I was all set to pick the Oilight M30 as my next light until I read the complaints about the PMW on this model. Apparently it can be noticed.
DeadButAlive
Newly Enlightened
There are some efficiency advantages to lower PWM frequencies that arise from the effects of gate capacitance in the switching FETs (much more can be said about this), plus the microcontrollers must run at higher clock speeds to attain higher PWM frequencies and they use quite a bit more power at higher clocks (its not a linear relationship between clock speed and power consumption) - thus there are trade-offs to be made. There are most likely economic reasons as well, I'm sure low gate capacitance FETs cost more and I know more power efficient micros cost more.
I agree that low PWM frequencies are very annoying. I recently returned an M20S to the relailer in exchange for the M20 (non-S) model because I could see the PWM at the low and medium levels. Frequencies in the kHz ranges should be more-or-less undectable and don't introduce that much loss overall, so I really can't see why a manufacturer wouldn't at least get out of the hundreds of Hz ranges... :shrug:
AnAppleSnail
Flashlight Enthusiast
TLAs are important. Pulse Width Modulation, not PMW. That'll keep you from getting no search results when you go looking 
On 11/12/2009, 4Sevens posted this very interesting info here on CPF.
About his Quarks vs. Preon circuits.
http://www.cpfmarketplace.com/mp/showpost.php?p=2388756&postcount=327
About his Quarks vs. Preon circuits.
http://www.cpfmarketplace.com/mp/showpost.php?p=2388756&postcount=327
tolkaze
Enlightened
I also notice PWM when using a video camera (well, one of three cameras... my Sanyo waterproof is susceptible) For filming under torch light, I use my ET M2C4, if you take the bezel off, it can accept 58mm filters (hoya at least) so I can stop down light with ND filters and colour it slightly with my gel filter holder.... just need a better stand and a better diffuser and it would make a good portable studio light
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