At 06:37 AM 11/27/04, "Joe K1IKE" <[EMAIL PROTECTED]> wrote:
>Heating: I use a 40 watt light bulb in my repeater
>for heat. I have it plugged into a "Freeze Alarm"
>unit and set it to 55 degrees. The Freeze Alarm is
>something used up in the North that you normally plug
>a light into and put the light in your front window.
>If your heat goes off while you are away in Florida
>for the winter, it will alert your neighbor that there
>is a problem with your heating system. This works
>well and I probably will put two of these in my
>repeater this year. Last year, the light bulb burnt
>out a couple of times, probably from being turned on
>and off so many times.
Joe...
My folks had a swimming pool in the back yard of
their souther calif. home and the 400 watt bulb in
the underwater light used to burn out every 8 months.
Changing it was a major PITA due to the poorly
designed waterproofing of the fixture. And the bulb
was a special shape for pool lights, and was $20
(and that was in 1970 vintage dollars).
My solution was to reduce the frequency of the
burnouts. I took a ceramic heating element with a
light-bulb-screw-base and stripped it of 80-90% of
the nichrome wire and put it in series with the
pool light so that the voltage across the bulb was
around 100 volts.
That was in 1983. The same bulb is still in service.
Another trick was used by IBM on the old
(1970s and 1980s) mainframe computers
that had hundreds of incandescent bulbs on
the front panels. Their research said that the
bulbs burn out due to the inrush current into
the cold, low resistance filament. The resistance
ramps up rapidly with filament temperature.
Their solution was to add a resistor in parallel
with each open collector lamp driver so that the
current through the resistor kept the filament at
a dull, dull red, and the driver transistor shorted out
the resistor for full brightness.
You could also take advantage of the fact that it's
an AC circuit and put a capacitor in series with the
light bulb to change the voltage vs current phase
angles.... Don't know the value, but years ago
when I worked on tube-vintage Moto base stations
that had green and red "bulls-eye" panel lamps
for power and PTT on the front panel I found
a cap in series with the green power light on a
couple of stations...
Those with the cap never burned out, those without
had a box of bulbs that were left with the dispatcher.
Mike WA6ILQ
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