Jinx wrote:
>
> Twice this week I've had my work spotlight bulb blow when I turned
> it on. Other spotlights in the house seem to fail more often than
> ordinary bulbs, and quite regularly. And I'm sick of it. The other day
> I said I thought that cold filaments are more likely to burn out if
> power was applied at the peak of the mains cycle. Is this true ?
>
> Is there a simple non-PIC solution to reduce this stress or reduce the
> 230V down by 10% (which would significantly increases bulb life) for
> a 60W bulb. A series resistor sounds like it should work, but are there
> any real safety concerns with a few watts of heat and/or regulations
> that prohibit this
>
> I'm peed off enough, if all else fails, to make a PIC circuit that will
> allow initial power to the bulb only at 0V (and I don't care if I don't
> break even in the long run. The satisfaction of almost never replacing
> a bulb is quite appealing right at this moment)
>
> Any comments or experiences ? One other thought was to replace
> filament bulbs with the more expensive fluorescent bulbs, although
> I've always felt they're "a bit cold"


Yes. Spots are notorious for blowing often when turned
on, low life and low vibration tolerance. We had them
on the awning for one of our shops and they blew every
few weeks. Try to keep them cool if possible.

For startup, just use a resistor? Why didn't anyone
mention this? I thought it was common knowledge. The
cold filament has a very low resistance, and startups
kill bulbs. A resistor that drops 5% volts at running
will give a very soft start.
230v/60w=261mA, drop 5%=11.5v=44ohms@3w (use 10w or
2x5w). Remember a 5w resistor run at 1.5w will get
quite hot. Keep them away from the bulb.

You will get *huge* bulb life improvement from this.

-Roman

PS. We had the high efficiency bulbs in a shop, they
blew all the time too. The light fittings were recessed
into the roof, and they got hot. Don't use these
electronic ballast things anywhere they don't have
enough cooling airflow.

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