Yeah, vibration, knocking etc.
In Australia our main type of globes are not screw in but bayonet. (push in
& 1/4 turn).
Most globes here for household type use only have 3 supports holding the
element up. It is possible to get ones that have 7 or 8 supports & these can
take much more rough treatment. They are designed for "trouble lights" for
mechanics etc.
Another recent type of globe has just recently taken over the trucking scene
here in Aussie is a type of LED light but I doubt if it would be bright
enough for your purposes. They last "forever" on truck side light useage.
BruceM


"Leanne" wrote in message
...

"Tom Best" wrote in message
om...
I would appreciate some help with a 12 volt question.

I would think it would be from excessive vibration if they were
originally for fixed service in the yard.

Leanne

Thanks for the info. Small (important?) corrections and additional
info follows:

Seven bulbs in paralled and are 25 watts, not 40 watts. Resulting in
a total of 175 watts on a 300 watt transformer. However, one bulb
still burns at regular brightness.

The copper wire is 12 guage and stranded. About 30 feet long.

I though the low voltage yard lights were transformed to 12 volt DC
not 12 volt AC. Is that the issue?

Tom

"Tom Best" wrote in message
om...

I though the low voltage yard lights were transformed to 12 volt DC
not 12 volt AC. Is that the issue?

The light bulb would not care if it got 12 VDC or 12VAC.

It might help if you provided more detail on the "DC Converter".

Why are you using a DC converter instead of a simple AC transformer?

You said it was made for this so one would assume the voltage is correct,
but you should measure it anyway. Have the lights been on 24 hours a day, or
just a few hours each evening?

Light bulbs are rated in number of hours they can be expected to last. Some
light bulbs will last thousands of hours. Others, like a projector bulb for
example, may last only tens of hours.

Heat, shock and vibration are reasons for premature bulb failure. Some
bulbs are not rated to operate in an "upside down" position, as it will
cause the base to overheat. Make sure that the bulb is not being used in an
inappropriate application.

Perhaps if you told us exactly what bulbs you were using it would help. You
said they were in a screw base, are these the 12volt bulbs that are often
used in RVs or boats?

Rod McInnis

My apologies to all for bothering you with a stupid question. The yard
light converter converts from 120 V. AC to 12 V. AC. Not DC as I assumed.

I never would have guessed. Thanks for the help.

Tom


"Calif Bill" wrote in message
link.net...
Check the voltage. My Malibu is 12V AC from what I remember.

"Tom Best" wrote in message
om...
I would appreciate some help with a 12 volt question.

I set up a 7 light long string of 12 volt, 40 watt bulbs on a strand
of 12 guage, outdoor lighting, copper wire. The bulbs and bases were
standard Edison screw base types. The lights were connected to a 300
watt DC converter made for outdoor yard lights. In theory, I would
like to take the same string (with lower wattage bulbs) on sailing
trips.

In 4 days, 6 of the seven lights have burned out. One light continues
to burn at normal brightness.

Any ideas or comments on these failures apprecitated.

Thanks
Tom

Thomas,
your query remains as sensible as it did before you mentioned the AC
output. The lamps would have failed from overvolts (not much is
necessary!) or vibration - whether the supply was AC or DC.

Brian W

On Wed, 03 Dec 2003 00:33:11 GMT, "test"
wrote:

My apologies to all for bothering you with a stupid question. The yard
light converter converts from 120 V. AC to 12 V. AC. Not DC as I assumed.

I never would have guessed. Thanks for the help.

Tom


"Calif Bill" wrote in message
hlink.net...
Check the voltage. My Malibu is 12V AC from what I remember.

"Tom Best" wrote in message
om...
I would appreciate some help with a 12 volt question.

I set up a 7 light long string of 12 volt, 40 watt bulbs on a strand
of 12 guage, outdoor lighting, copper wire. The bulbs and bases were
standard Edison screw base types. The lights were connected to a 300
watt DC converter made for outdoor yard lights. In theory, I would
like to take the same string (with lower wattage bulbs) on sailing
trips.

In 4 days, 6 of the seven lights have burned out. One light continues
to burn at normal brightness.

Any ideas or comments on these failures apprecitated.

Thanks
Tom

Tom,

Nothing to apologize for. I tend to think that the AC in this case
would not harm the bulbs as Rod said. Do you have a multimeter that
you can use to check the converter to see what the actual output
voltage is? Also, where did you obtain these bulbs and what were
they marketed for?

-JimL



test wrote:
My apologies to all for bothering you with a stupid question. The yard
light converter converts from 120 V. AC to 12 V. AC. Not DC as I assumed.

I never would have guessed. Thanks for the help.

Tom

"test" wrote in message
...
My apologies to all for bothering you with a stupid question. The
yard
light converter converts from 120 V. AC to 12 V. AC. Not DC as I
assumed.

I never would have guessed. Thanks for the help.

Tom


AC/DC a light bulb doesn't know the difference. Remember the High
Intensity desk lamps? Tensor was a brand? A 12v AC supply and a tail
light bulb.

del cecchi

I would think it would be from excessive vibration if they were
originally for fixed service in the yard.
Agreed.

A good way to check for vibration is to set a dish of water near the bulbs,
rev up the engine while you observe ripples on the surface of the water.

I'd bet you'll see signs of excessive vibration at various throttle
settings. This is bad news for a hot filament (as you already know).


--
(¯`·._.· £ãrrÿ ·._.·´¯)



"Leanne" wrote in message
...

"Tom Best" wrote in message
om...
I would appreciate some help with a 12 volt question.

I would think it would be from excessive vibration if they were
originally for fixed service in the yard.

Leanne

Watts is a measure of power. Current is measured in amperes.

JimL wrote:

jean,

I'm confused on what you're saying. 40 watts is the current limit
for the bulb, period! Unless of course the voltage is too high
thereby forcing more current through. From what I see of these
outdoor converters, the voltage output is constant. Manufacturers
just don't want you to overdrive them with more wattage of bulbs
than the trancformer can put out.

-JimL

jean wrote:
TOM make sure that your circuit is a parrallel one, not in series.Also you
cannot reduce the watt of the bulb because you will reduce the resistance of
your circuit and let pass to much current on the same bulb (burning action)


"Tom Best" a écrit dans le message de
om...

I would appreciate some help with a 12 volt question.

I set up a 7 light long string of 12 volt, 40 watt bulbs on a strand
of 12 guage, outdoor lighting, copper wire. The bulbs and bases were
standard Edison screw base types. The lights were connected to a 300
watt DC converter made for outdoor yard lights. In theory, I would
like to take the same string (with lower wattage bulbs) on sailing
trips.

In 4 days, 6 of the seven lights have burned out. One light continues
to burn at normal brightness.

Any ideas or comments on these failures apprecitated.

Thanks
Tom

On Tue, 2 Dec 2003 14:01:11 -0800, "Rod McInnis"
wrote:


"Tom Best" wrote in message
. com...

I though the low voltage yard lights were transformed to 12 volt DC
not 12 volt AC. Is that the issue?

The light bulb would not care if it got 12 VDC or 12VAC.

I'm going to go out on a limb here. Assuming the voltage is in the 12
Volt range and the bulbs are of reasonable quality, there might be a
difference between AC & DC regarding these bulbs.

A 12 Volt bulb (automotive/RV type) running on AC is being turned on
and off 120 times per second (60 Hertz). Although way too fast for
general themometers, it's also experiencing a temperature change 120
times per second. By design, the bulb may be designed to withstand the
vibration associated with auto/RV applications, but not the super
rapid temperature changes.

I've noticed a similar scenario with garden lights. They use the exact
same type automotive bulbs used in some tail lights, yet last only a
fraction of the (relative) time. To save money, the transformer output
is AC, eliminating the bridge rectifier and smoothing capacitor.

I would guess that were the same string of lights hooked up to a
"smooth-ish" 12 Volts of DC, as experienced in a car charging system,
they would outlast the 12 Volts AC system every time. A liberal
sprinkling of diodes, chokes & capacitors will go a long way to
increasing the life of your bulbs.

FWIW, Tungsten filament bulbs are not the most efficient means of
lighting an area. They produce a great deal of wasted heat.

Regards.




It might help if you provided more detail on the "DC Converter".

Why are you using a DC converter instead of a simple AC transformer?

You said it was made for this so one would assume the voltage is correct,
but you should measure it anyway. Have the lights been on 24 hours a day, or
just a few hours each evening?

Light bulbs are rated in number of hours they can be expected to last. Some
light bulbs will last thousands of hours. Others, like a projector bulb for
example, may last only tens of hours.

Heat, shock and vibration are reasons for premature bulb failure. Some
bulbs are not rated to operate in an "upside down" position, as it will
cause the base to overheat. Make sure that the bulb is not being used in an
inappropriate application.

Perhaps if you told us exactly what bulbs you were using it would help. You
said they were in a screw base, are these the 12volt bulbs that are often
used in RVs or boats?

Rod McInnis