> -----Original Message-----
> From: Jinx [SMTP:joecolquitt@CLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 9:37 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> 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"
>
>
How about an NTC thermistor? High resistance to begin with so switch on
surge current to the lamp will be low.  As the thermistor heats up it's
resistance decreases and applies more power to the lamp.  I think the
concept is ok, but wether you could find a suitable thermistor is another
matter all together...

Alternatively you can get an opto isolators with built in zero crossing
detection and relatively high power triac outputs.  Might be able to rig one
of these up to ensure your lamps always get switched on at the zero crossing
point.

Mike

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