So you wanted to know what PWM is? (NEW video inside)

This is a video of a working prototype of my upcoming flashlight converter.

One interesting detail on this video, and the reason I made a separate post for it, was provided by the digital camera I used (Lumix FZ7): the converter levels are controlled by PWM (Pulse wide modulation), if you look at the lens glow on high level you will see no gaps in it (100% duty cycle), but then when I switch to med (50%) and low (2%), you can clearly see how the glow shows the amount of ON-OFF that makes the LED dim.

This is the best visual explanation I ever saw on PWM, and it happened by simply serendipity.

Google Video Link (Better Quality)
Youtube Video Link

Enjoy it.


Pablo

Re: So you wanted to know what PWM is? (video inside)

Great post Pablo. Thanks for the video.

Re: So you wanted to know what PWM is? (video inside)

The link crashes my IE window

Re: So you wanted to know what PWM is? (video inside)

I added another video link Chris, it should be available pretty soon, Youtube is processing it as I write this.


Pablo

Re: So you wanted to know what PWM is? (video inside)

cool effects.Thanks for sharing that

C

Re: So you wanted to know what PWM is? (video inside)

fnmag said:

Great post Pablo. Thanks for the video.

Click to expand...

+1 :thumbsup:

Re: So you wanted to know what PWM is? (video inside)

yeah, really cool !!

Re: So you wanted to know what PWM is? (video inside)

very nice

Re: So you wanted to know what PWM is? (video inside)

Cool indeed stinky. :nana:

Re: So you wanted to know what PWM is? (video inside)

wow. I noticed the same effect when pointing my FF3 at my Sony DCS-W50. I didnt realize what I was seeing. thanks for the enlightenment!

Re: So you wanted to know what PWM is? (video inside)

You mean you didn't add that pink glarish line??? O btw thats damn cool what do you prefer and ultra high frequency pwm rate or a lower rate. I would assume that a super high rate would kill the led and as would a super low rate I suppose you found a safe good range? O also nice work.

Re: So you wanted to know what PWM is? (video inside)

I didn't added the glare, it was the camera that saturated

The frequency used is 400hz and Im almost sure you can't see the flicker at this frequency, and no, the led does not suffer used this way.

The glare in the video shows the duty cycle, not the frequency, it probably shows a multiple of the frequency, the video was taken at 30 frames per second, I guess if I use 300hz for the PWM rate the glare would stand still... :thinking: I will make a new program just for this, looks like an interesting test


Pablo

Re: So you wanted to know what PWM is? (video inside)

Cool indeed

Yesterday by simple serendipity I discovered that when the camera saturates with the power LED glow, it shows the duty cycle of the LED being PWMed, so I made this second video to show more PWM levels.

Also by calibrating the PWM frequency with the camera frames per second I managed to almost freeze the glow (in the first video it moved)

Hope you all like it.

Youtube Video

Google video (better quality)


Here is the code I used for the video:



Pablo

:goodjob:

Thanks for the video!, I can see the PWM of my LH with my bare eyes when I shine it on a reflective surface during use.

AlexGT

Very cool video Pablo :rock:

Will

AlexGT said:

Thanks for the video!, I can see the PWM of my LH with my bare eyes when I shine it on a reflective surface during use.

AlexGT

Click to expand...

The LH runs PWM at close to 800Hz. Can't imagine too many surfaces that would allow you eyes to see the PWM unless you were moving the light around rapidly ->

You can see PWM very clearly if you have a LED light that uses it. Just set the light on low and then swing it back and forth in an arc while looking at the LED. You'll see essentially what's on the video - on/off segments.

Of course with an oscilliscope you can observe the same on/off pulse train as you vary the duty cycle.

Old strobe tricks, if you vary the PWM frequency and shine at a moving object like fan blades you can make them 'freeze', vary the frequency a little and you can make them look like they are slowly moving forwards or backwards.

george.

Love the videos, especially the title cards! (no, I'm not old enough to have seen silent films at a theatre......)

On a similar note I have noticed that the led light clusters which buses around here use for rear lights can be seen to flash on and off on video recordings. The effect is quite odd as they seem to do so at random intervals, presumably as the video frames catch the "off" portion of the duty cycle.

Looking forward to seeing in a light Pablo!!