[RFI] 120v halogen lights

[Ron Rossi]

It is refered to as electromigration at least within the semiconductor 
design industry. It is an issue we take into consideration when 
designing the wiring of our circuits.

-- 
73 es God Bless de KK1L...ron (kk1l at arrl.net)
ASIC PE IBM Microelectronics
<><
QTH: Jericho, Vermont
My page: http://www.qsl.net/kk1l


stuart benner wrote:

>The reduction in life of an incandescent lamp when operated on DC versus AC is
>attributable to a phenomenon known as "DC notching." With DC applied, the
>tungsten molecules migrate within the filament and the filament takes on a
>"notched" appearance. The increased local resistance at the notch points along
>with the reduced physical strength result in decreased life. If AC is applied to
>the filament, this condition is avoided. A lamp operating on DC may have 20% to
>50% of the same lamp operated on AC.
>
>Much research was done on this at NASA-Goddard by their lamp expert Dr. Henning
>Leidecker. One of the life-limiting factors on the earlier GOES spacecraft (and
>others) was the life of the black bias (incandescent) lamp in the satellite
>sensors.
>
>Stu Benner
>W3STU
>
>Quoting Martin Ewing <martin at aa6e.net>:
>
>  
>
>>OK, I've heard this said before.  But inquiring minds want to know:  why 
>>should DC be worse than AC for lifetime in lighting applications?
>>
>>I seem to recall it was an issue for vacuum tube filaments, presumably 
>>because having a DC gradient on the filament led to unequal 
>>concentration of emission on the filament.  (On the other hand, AC 
>>supplies could lead to hum.) But in a lighting situation?
>>
>>I can think of a couple reasons why DC might be better: no AC-induced 
>>vibration, unity peak to average power, etc.
>>
>>73 - Martin, AA6E
>>
>>    
>>
>>>Subject:
>>>Re: [RFI] 120v halogen lights
>>>From:
>>>"Tom Rauch" <w8ji at contesting.com>
>>>Date:
>>>Sun, 4 Apr 2004 10:23:22 -0400
>>>To:
>>><rfi at contesting.com>, "Pete Smith" <n4zr at contesting.com>
>>>
>>>
>>>      
>>>
>>>>I assume that there is no reason why any real transformer that delivers 
>>>>12.6vac couldn't be used -- perhaps even an AC wall wart.
>>>>   
>>>>
>>>>        
>>>>
>>>That's right, as long as it is AC. If you run DC bulb life is shorter.
>>>
>>>73 Tom 
>>> 
>>>
>>>      
>>>
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>>    
>>
>
>
>
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