OT:Extending light bulb lifetimes

It is what happens in the mind of George Dubbuyaw every time he looks in the mirror ;-)

Regards, Tony

It depends on which part of the sine wave you close the switch at. If it is at the zero-crossing point then no current will flow at all in the instant the switch contacts close, but at any other point on the sine wave there will be current flow, reaching maximum at the crest of the sine wave. This is one of the reasons for using zero-crossing point switching circuits to reduce interference.

Not a myth, it is based on fact, but the likelyhood of you always hitting the zero-crossing point is pretty slim, bearing in mind that you have 360 degrees of sine wave to hit when you turn on.

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Sorry, possibly bad terminology. Both me, and I suspect everybody else are referring to the sudden application of voltage to the bulb via a switch rather than the gentle ramp up of a nice A.C. sinewave, which can cause an inrush of power to a cold filament, thus momentarily increasing the power taken by the device.

Best Regards

Tom.

Nunce excretia in extractum est.

Amount of power on current is irrelevant to bulb life since filament regulates that current as required. Current is initially high because filament is cold. But temperature of filament (not current) determines how filament vaporizes. Inrush current quickly drops as filament warms.

Zero voltage switching using triacs is extremely important if you want to avoid interference during switch on/off. It is probably useful for all sorts of other reasons, but in equipment used anywhere near audio gear it is used to avoid interference. I used to run a mobile disco, and everything had to be switched this way or it caused problems (for simple on/off switches you could get away with suppressors).

Regards

Kevin

I've felt the gentle ramp up of an electricity board sine wave on more than one occasion. I get chest pains thinking about it...