🚀 go-pugleaf

In article <s9MTj.40$wj3.23@newsfe06.lga>, 
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net says...
> Mark wrote:
> 
> > On May 5, 9:36 am, a7yvm109gf...@netzero.com wrote:
> > 
> >>On May 5, 7:24 am, "Phil in Melbourne" <reply@tonewsgroup> wrote:
> >>
> >>
> >>>So I would have thought that this would be a simple problem but the more
> >>>information I get the more I get confused......
> >>
> >>>I want to PWM a whole lot of LEDs. The current consumption of the bank of
> >>>LEDs is in the order of 15 Amps, at 12V.
> >>
> >>>For reasons I won't go into, my only option is to use a high side mosfet.
> >>
> >>>I have chosen an N-channel MOSFET (IRL3803) mainly because of its huge
> >>>current capability and very low on resistance of 7 milli ohms.
> >>
> >>>I am hoping to use PWM at a reasonably high frequency, say 20khz or higher,
> >>>and I want to use an efficient MOSFET driver IC that is designed for the
> >>>job.
> >>
> >>Why so high? If it's just for brightness control, you don't need that
> >>surely?
> > 
> > 
> > if you strobe LEDs too slow, then it causes a strobe effect if there
> > is any  movement... if you scan your eye past some LED rear car lights
> > you can get the strobe effect and it is very annoying... even if the
> > LED is not moving, your eye is always moving
> > 
> > I don't know how fast you need to pulse to avoid this but a few
> > hundred Hz is too slow.   5 kHz might be OK  I don't know...
> > 
> > At 5 kHz you might get audio interference so that is a good reason to
> > go to 20 kHz.
> > 
> > Mark
> 32 frames/Sec I believe is the minimum needed to prevent strobe flash in 
> the human eye.. or some figure like that.

Not at all.  Movies use 24fps, but open the shutter two or three 
times per frame to eliminate the flashing.  TV interlaces 30Hz 
frames with 60Hz fields for similar reasons.  
  
-- 
Keith