>>> PWM Frequency List <<<

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EngrPaul

EngrPaul

Flashlight Enthusiast
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The following is a list of measured frequencies for various flashlights. This will be updated as people contribute.

Jetbeam CL-E (AA): 73 Hz [Strobe mode is 8 Hz]
Jetbeam C-LE v1.2 (AA): 315 Hz [Strobe mode is 8 Hz]
Fenix L0 multi-level series (AAA): 100 Hz [Strobe mode is 8 Hz]
Fenix L2D Series (2AA): NO PWM [Strobe mode is 8 Hz]
Fenix P1D Series (123a): NO PWM [Strobe mode is 8 Hz]
Huntlight FT-01-XRE (2x123a): 186 Hz [Strobe mode is 8 Hz]
Photon Freedom (2x2016): 185 Hz
FluPIC v2.2: 195 Hz
SafeLight SuperBright (9V): 1149 Hz
Inova Microlight: 95Hz
ALX-233C 3xC 3W: 128Hz
Streamlight Tasklights: (3AAA, 1AA) 189Hz [Strobe mode is 3 Hz]
LED Logic Striker-VG: 150~180 Hz [Strobe mode is 9 Hz]
Inova Microlight: 97 Hz [strobe mode is 3 Hz]
Freedom X-light micro: 185 Hz [strobe mode is 11 Hz]
HDS B42: Burst: no PWM, Primary: no PWM, Secondary: 1161 Hz, lowest level: 448 Hz
LiteFlux LF2: 7670 Hz
Nuwai 654C and 352: 9910 Hz
JetBeam MkIIX: 120Hz [12/14/5 strobes]
Jetbeam MKII (no X) 95 Hz [strobe mode is 14 Hz]
Rexlight 2.0: 94 Hz [strobe mode is 10 Hz]
Dexlight X.1: 120Hz [12/14/5 strobes]
Dexlight X.V: 73 Hz [strobe mode is 8 Hz]
Jetbeam JET-u (AAA): 315 Hz [Strobe mode is 8 Hz]
Photon Photon (AA): 197 Hz

[The strobe numbers are for the intentional pulsting mode of the flashlight, not related to PWM]

For those of you who don't know what PWM is, it's "Pulse Width Modulation". Instead of the flashlight circuitry dimming the LED by supplying less power, it "pulses" the emitter on and off rapidly. So instead of supplying 10% of the power 100% of the time, it's supplying 100% of the power 10% of the time.

The assumption here is that the eye has enough persistence of vision to not notice the pulsing on and off.

The "dislike" of PWM is either (1) the frequency is too low, and persistence of vision isn't enough to remove the flicker by the viewer, or (2) there is relative motion between the flashlight / environment / viewer, in which a pulsing light becomes more obvious.

Consider the case of two flashlights which are waved in front of a camera on extended exposure. The top one (Fenix) has a slower PWM frequency. The pulses on and off are more obvious to the user. The bottom one (Huntlight) has a faster frequency. It's less likely to be objectionable to the viewer.

PWM_Huntlight-Fenix.jpg


Again, the lower the frequency (Hz), the more noticeable the pulsing is.

How can frequency be measured? Well, if you don't have an oscilloscope, I have an easier method for you. If you have a digital volt meter with a "Hz" or frequency setting, hook an LED up to the leads and shine the flashlight on the LED in a dimmed setting (one step below maximum). LED's just happen to produce a small voltage when light is shined on them (somewhat like a stereo speaker can work like a microphone). Here is a picture of the setup, in which the meter is reading ".186 k Hz" (=186 Hz):

IMG_1042.jpg


I found that the LED is not sensitive enough for measuring lower light levels. Perhaps a solar cell would work better(?)

The goal of this post is to collect together PWM frequency data for different flashlights for member reference.

Comments and suggestions welcome :)
 
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Hey could you messure the frequency of the strobe on the lod when you have a spare moment. Im guessin it's at around 10Hz or less.

Cheers.
 
Hi EngrPaul - excellent idea, and I'd second adding strobe data to the list.

I tried this technique last night, but couldn't get the setup to work with my DMM. When I hook the leads up to an LED, I can detect a voltage deflection in the presence of light (although it's not stable - shows a strong drift corresponding to the brightness of the light). But my Hz mode continues to read 0. I'll try again tonight with another LED, but I'm not sure what the problem is. Any thoughts?
 
I've added all the PWM data for flashlights I own. The Fenix AAA's all came in at 100 Hz on the button. I'll try to collect strobe data too, if possible.

selfbuilt- try using a different LED, maybe colors work too (green?) reposition things too. Make sure the light is straight at the lens so it converges on the LED chip. Also try swapping + and - leads. In the picture above the - is connected to the the cathode.
 
the frequency might just be too low for your DMM. i've seen only a few that have a range lower than 1kHz, and some just have a bad resolution/accuracy in the 1kHz range.
 
errr....on second thought it's more probable that your DMM requires TTL levels (>2,7V) for correct measurement on the frequency range, you might check that.
 
Hi EngrPaul & doc ... I suspect it's the LED (cheap white DX type used in fauxtons). I tried reversing the LED leads, to no effect. I also tried all the permuations my DMM allows for frequency/Hz measurements, including the alternate Hz~V setting for input scope >30V rms & <1kHz, all to no avail. My DMM is supposedly rated for 10Hz to 10MHz, so I suspect it's the LED. I'll try tonight with the coloured LEDs and see what happens.
[EDIT #1: I'm thinking it's possibly the signal requirement needed from the LED source - my DMM manual says I need >=200mV for Hz readings when on the Hz~V setting, and I don't think I was consistenly getting that from the LED. Not sure of the requirement for regular Hz setting, though].
[EDIT #2: Thanks Craig, I'll also try some of my colour LEDs tonight]
 
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selfbuilt said:
...I tried this technique last night, but couldn't get the setup to work with my DMM. When I hook the leads up to an LED, I can detect a voltage deflection in the presence of light (although it's not stable - shows a strong drift corresponding to the brightness of the light). But my Hz mode continues to read 0...
Click to expand...
Be certain that the LED you use is not a white LED.
Red, orange, yellow, or yellow-green LEDs would lend themselves well here.
 
Success! I used a red LED and was able to get stable Hz measurements.

Like EngrPaul, I've found only the highest intensity light levels would give a reading. I don't have the huntlight, but I can confirm EngrPaul's readings on the L0D-CE & C-LE.

JetBeam C-LE: 73.1 Hz on primary (aka medium)
7.66 Hz on strobe
Fenix LOD-CE: 99.8 Hz on primary (aka medium)
8.34 Hz on strobe

I tried the Streamlight tasklight 2AA, but intensity on low and strobe was too low to get a reading. I did managed to get a reading on my Photon Freemdom X-light micro:

Photon Freedom: 184.6 Hz on setting just below maximum
91.2 Hz on strobe mode
(doesn't make a lot of sense on strobe, but it oscillated a lot around 10-40 Hz before finally settling on 91.2Hz. May want to discount this one due to low light intensity?).

According to the voltage scale on my DMM, it seems I need a light to register ~0.6V intensity off the red LED before it gives me a stable voltage reading and allows Hz readings to be made. Below that, the voltage indicator sways madly, and no Hz reading can be made.
 
A few more for you:

Fenix L0P-SE: 99.1 Hz on primary (aka medium)
Fenix P1DCE: 8.03 Hz on strobe
Fenix L2DCE: 7.82 Hz on strobe

The LOP-SE on primary seems to be absolute lowest light intensity I can detect to get a Hz reading (0.6V exactly). You have to carefully align the LED right on the center of the lens to have a chance at a stable reading.

I'll try a few other color LEDs and see if anything changes.
 
Am I correct the L2D-CE doesn't use PWM? Please verify :)
 
Art Vandelay said:
Thanks EngrPaul. Could you please measure the frequency of the Surfire A2's PWM? I bet most people don't realize Willie Hunt's PWM engineering genius is behind the A2. http://www.candlepowerforums.com/vb/showthread.php?t=107943
Click to expand...

Are you asking me to measure the PWM of the incandescent bulb? I don't think you can do it externally because the filament stays hot between pulses.

As usual, correct me if I'm wrong. :grin2:
 
selfbuilt said:
Photon Freedom: 184.6 Hz on setting just below maximum
91.2 Hz on strobe mode
(doesn't make a lot of sense on strobe, but it oscillated a lot around 10-40 Hz before finally settling on 91.2Hz. May want to discount this one due to low light intensity?).
Click to expand...

Do you think it's pulsing AND strobing at the same time?

I want to measure a safelight but I have to dig around for some colored LED's, 'cuz the white one ain't workin'
 
EngrPaul said:
Do you think it's pulsing AND strobing at the same time?
Click to expand...

I'm not sure what's going on with the Photon Freedom. As I said, the strobe readings would vary from 10-40 Hz, then suddenly lock at 91.2Hz. It's definitely a faster strobe than the Fenixes, but it's not that fast, it seems to me.

As for the P1DCE & L2DCE, I know they don't use PWM - but I was just trying to measure strobe frequency. :)

It's a pity the SL-TL 2AA was too low intensity - I quite like the strobe freq on that light (lower than the Fenixes). I'll let you know if my other coloured LEDs do any different.
 
Just tried green and purple LEDs - no dice. Seems only red is sensitive enough.

BTW, I approve of your limits on significant figures (or digits, as the kids say today). The numbers I report are given to the precision that the DMM reliably gives (i.e. I do multiple tests). Of course, who knows how accurate that really is - so I agree with your decision to limit the sig figs to whole numbers.

It's a pet peeve of mine how people like to report output, lumens, etc to several decimal places, when that precision is clearly not available in their own instrument (i.e. if they do repeated tests, there's no way they are reproducing that). Not to mention there's no way of confirming accuracy to a true value.

Well done on a fun exercise - I'm looking forward to seeing results on other lights.

P.S.: Can you measure the huntlight at one more intensity level down? I'm curious if different PWM freqs are used for different intensities - none of my lights have more than one PWM mode that I can detect with my setup.

[EDIT: on further testing, I think the problem with the SL TL-2AA is simply that the strobe rate is too low for the DMM to pick up. My Inova microlight is similarly undetectable in strobe mode, despite providing enough voltage intensity to register on the DMM. Both lights tend to strobe around ~3 Hz, according to my manual counting with a stopwatch]
 
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The_LED_Museum said:
I do not own or have access to a DMM with Hz or frequency settings, so I cannot test in this manner. :shakehead:
Click to expand...

Sorry to hear that Craig. Here's one for $20. The specs are here and says Range=20KHz, Resolution=10Hz, Accuracy= 1.5% of reading / 5 digits, sensitivity .2V RMS and input max 10V.

Please put March 4, 2007 in your LED Museum as first date LED's were used as transducers in a PWM frequency measurement. :grin2:
 
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