[ale] More on LEDs...

[Michael H. Warfield]

On Wed, 2013-08-14 at 09:11 -0500, Doug Hall wrote: 
> I just had my air conditioner replaced yesterday, and the AC guy said
> something that I thought was interesting. He said that Alabama Power
> (my provider) was fairly good at producing power inexpensively, but
> bad at distributing it. He said that rather than the supposed 60hz
> that they're supposed to deliver, it's usually a little less than that
> - say around 58-59Hz. It's usually close enough to not fry everything
> from brownouts, but also low enough to lower the longevity of things
> like these energy-saving lights that are supposed to last ten years.
> This has been my experience, by the way. They tend to go bad after a
> couple of years (maybe).

1) That should be easy to check with any half way decently frequency
meter.  Even my cheapo Radio Shack DVM has a frequency test scale.
You're talking well over 1% off on frequency (closer to 2% or 3%)...  A
decent frequency meter will be crystal controlled and can tell you to a
very small fraction of a percent.  Even a Raspberry Pi with their
ceramic oscillator and an audio input can give you that resolution (part
of my little RPi power line monitor project - which is still in progress
but delayed due to outside issues).

2) CFL's run on high frequency RF (high efficiency switching supply).
Power has to be rectified and then feed to a high frequency switcher.
THAT's what makes dimming a CFL such a huge PITA.  It takes additional
power duty cycle conversion circuity to convert the thyristor (duty
cycle) or rheostat (resistance) dimmer into high frequency duty cycle
for the tube at high voltage.   I can't see power line frequency having
a significant effect there.

3) LED's are fundamentally DC.  Power has to be rectified, filtered, and
regulated.  I can't see power line frequency having an effect here,
either.  Much simpler circuitry than a CFL.

4) US is on 120VAC/240VAC @60Hz but much of the rest of the world runs
on 50Hz and a lot of the circuitry can handle 50Hz and lower with no
degredation.  Most manufacturers are going to want to use common modules
in a wide variety of packages (which is why you now see so many wall
warts that take 80VAC - 250VAC and can function) just for inventory.
Even where they are pre-wired for 120VAC/60Hz, the internal circuitry
can generally handle a much wider range.

5) If they were consistently that far off, you would notice it in clock
drift of almost every line driving clock in your home.  You'd notice
that before you'd notice problems with your lights.

6) Only lower in frequency?  If they're drifting that much, I would bet
it's both plus and minus.  This may have changed from when I was in the
broadcast business (all our clocks were power line drive and checked
daily against WWV) but power companies could "drift" but they would also
have to drop or make up cycles on a daily basis so the number of cycles
would count out properly for a 24 hour day.  Even if they were +- one or
two Hz, they were going to hit 5,184,000 cycles in a 24 hour period.

7) I'll BET that he really meant "energy saving appliances" and NOT
"energy saving lights".  There's a big difference.  Motor driving
appliances can be impacted by power line frequency (though even my pool
pumps are rated for 50/60Hz 120/240VAC).  Lower frequency can result in
slight increase in heat generation and lower efficiency but, even down
the 50Hz, shouldn't be a killer.  If he said "appliances", I would cut
him some slack.  If he said "lights" I would accuse him of a
non-sequitar and improperly extrapolating from "appliances" to "lights".

OLD, large core, transformers, I can see degrading at 50Hz but not
significantly (58/59 Hz - trivial).  They would get a little warmer.
Most modern compact devices are going to want to get that power
rectified ASAP to keep component sizes to a minimum.

OTOH, voltage can have an effect on efficiency.  110/115/120 is all
considered the same and that's +- 10% and can drift outside that without
anyone batting an eyelash.  If standard US single phase is within 105VAC
to 125VAC, I doubt many would even notice a flicker (which is why you
need power line monitors - it's common).

I also experience premature failure of CFLs but it's almost always been
heat related circuitry failure or tube wear-out due to duty cycle.
Almost all of the CFL's I have seen are rated for 7.3 years at a duty
cycle of 3 hours per day.  If you leave them on continually, divide by 8
and subtract the additional heat buildup in enclosed fixtures.  If they
are turned on and off frequently, they're going to experience thermal
shock which can shorten the life of the CFL (much less so LEDs).  You
might see 7.3 years if you run a CFL 3 hours per day with one turn on
and one turn off per day.  The rest of us are going to experience much
less.  My CFLs in our kitchen and in our ceiling fans have a high
failure rate (kitchen can lights - two years tops) largely due to duty
cycle burn-out.  The LEDs I've replaced them with have yet to fail and
have lasted longer...  CFLs were very problematic in ceiling fans and
fixtures with vibrations (garage door openers).  LED's - big win.

> On Tue, Aug 13, 2013 at 4:38 AM, Jim Lynch
> <ale_nospam at fayettedigital.com> wrote:
>         On 08/12/2013 11:09 PM, Ron Frazier (ALE) wrote:
>                 I wish I could figure out a way to participate in the
>                 led market but the big box stores and online retailers
>                 eliminate most of the possibilities for little guys. 
>         There's always the niche markets, like RV and boat users  who
>         are looking for better ways to conserve power.
>         
>         Jim. 
>         
Regards,
Mike 
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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