[simpits-tech] RE: CP Clock

[Ben Jones]

Filament bulbs will yes work on both ac and dc current ,

the reason they will last longer on ac is because of the sinusodial wave form of ac current

 ( Bare with me and imagine if you wish to )
 
with dc currrent the electrical current or applied electrical pressure is constant, means the wave form rises once turned on then stays a a constant ish level in the positive area of the x and y axis.

with ac current because it oscillates between posative pressure through to no pressure then to negative pressure this provides a small cooling effect on the fillament,

eg : the voltage ac applied  starts off at 12v pos then drops to 0v then drops to -12v then back up to 0v then back to pos 12v , and then continues on a huge loop untill the voltage is switched off, because this happens the fillament for a nanosecond has time to slightly cool. 
adding to that as the voltage changes the current is proportional meaning as the voltage is high the circuit is operatingon a low amperage , then the voltage decreases to 10v and the amps go up further to 8 volts and then the amps incerase again, and hand in hand this works in reverse as the voltage increases the current starts high  as the voltage gets to peak level the amps will be minimal , this provides a "soft start" and a "soft stop" for the fillament which lenghens the life of the fimmanent.

with dc because the voltage and current are constant the fillament heats up and is not given any chance to cool at all highly decreasing there life span .

i can draw some diags and up load them to the simpits site  of the  wave form above explained in lay mans terms if any one would like me to   do just will take a couple of days due to work and mil commitments 

sorry if i have offended any ee people here , as this is only my understanding of my hoards of books in my library shelf , due to my trade



hope it helps



BEN   JONES 
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bjones@pipecomp.com.au
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-----Original Message-----
From: Roy Coates [mailto:roy@flightlab.liv.ac.uk]

some devices, like filament bulbs don't care if its AC or DC. However, I
seem to recall that bulbs driven with AC last longer - though I can't
remember why.

Roy.