🚀 go-pugleaf

On Thu, 11 Oct 2012 05:55:15 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Oct 10, 11:50�pm, Jeff Liebermann <je...@cruzio.com> wrote:
>> On Mon, 8 Oct 2012 06:27:05 -0700 (PDT), George Herold
>>
>> <gher...@teachspin.com> wrote:
>> >Hi SEB. �Well I sent an email to Don klipstein on this topic. �And
>> >have permission to copy his reply.
>> ><from Don K. below>
>> >2: �In incandescent traffic signals, the bulbs for yellow last
>> >longer than for red and green. �So even after being switched on
>> >and off about a million times, on-time is still a significant
>> >factor in life expectancy.
>>
>> That means for my proposed test comparing a 50% duty cycle flashing
>> light bulb, with one that is on continuously, the continuous light
>> bulb will burn out first. �That's the opposite of what I saw with the
>> theater marquee bulbs. �Now, I'm really tempted to run the experiment.

>Experiments can be very useful.

Yep.  However, it's more fun to predict, speculate, guess, reverse
engineer, and maybe calculate.

>I'd worry most about how you turn on the bulbs.
>Maybe just some simple relays?

No.  I didn't want to life test the relay contacts, just the light
bulbs.  I have plenty of solid state switches that will suffice.  The
reason I wanted two was to make sure the voltage drop across the
switch was the same for both the flashing and continuous bulbs.

>1,000 hours isn't all that long.  (or are you going to over-voltage
>the bulbs?)
>I guess I'd want at least 10 bulbs in each group.  Say 60 watts.....
>1200 kW-hrs.

Much as I would like to use a rack of bulbs, 
<http://pinterest.com/pin/172122016978363241/>
<http://pinterest.com/pin/172122016978761590/>
I think two bulbs will suffice for a start.  The plan of the moment is
to use a variac to boost the voltage from 120VAC to about 135VAC,
which should reduce the 1000 hr life to a more tolerable 112 hrs.
Cut-n-paste from a previous posting:

Instead, an accelerated life test can be done with higher than normal
voltages.  
<http://www.welchallyn.com/documents/Lighting/OEM_Halogen_Lighting/MC3544HPX_Catalog_2_11_09.pdf>
For halogen bulbs, they use:
  Life = (Vdesign / Vapplied)^12.0 * Life at design voltage
For a 1000 hr lamp running at 120% of the rated voltage, the life
might be:
  life = (1/1.2)^12 * 1000 = 112 hrs
which is more reasonable.

>That's looking like more money than I'd want to spend on the
>electricity.

I'm trying to determine where to run the test.  I don't want a
flashing bulb in my bedroom.  I also don't want to run an unattended
rack of bulbs in the office which could become a fire hazard. Methinks
just 2 bulbs and a 3-4 day accelerated test will be sufficient.

>George H.

-- 
Jeff Liebermann     jeffl@cruzio.com
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