landscape lighting
Don Yuniskis
Greetings!
OK, here's the scoop... I've got a bunch of these classy
landscape (low voltage) lights here that use small 20W halogen
bulbs. They are powered off an (unregulated and probably unfiltered)
12VDC (yes, not AC) supply (can you spell "big transformer"?).
Well, these little puppies have been blowing out. Unfortunately,
they run about $6 - $8 each to replace. This is Not Good (Tm.Reg.).
The problem doesn't appear to be systemic as there are bulbs in the
circuit that have been there since day one while others have been
replaced twice! Voltages differences don't seem to be a cause,
either, (i.e. IR drops in the cables) since some lamps with short runs
(i.e. low IR losses) are good while others are bad. Likewise for
lamps with *long* runs (high IR losses).
So, what gives??
I'm sorely tempted to make some adapters to allow bayonet base
automotive bulbs to be used in their place. With a dozen of these
suckers on the property, it's just too damned expensive to replace them
all at $6 a pop!
Thanx!
--don
P.S. Anyone have a good source for bayonet sockets with pigtails
and mounting brackets?
Rolavine
The wire lengths would not drop enough voltage to make any difference. I
would suggest that the voltage does make a difference, and that lowering it
would allow the bulbs to run cooler and longer.
>Subject: landscape lighting
>From: d...@rtd.com (Don Yuniskis)
>Date: 26 Sep 1997 02:15:10 GMT
>Message-id: <60f5re$s...@baygull.rtd.com>
Don Yuniskis
In article <19970926173...@ladder01.news.aol.com>,
Rolavine <rola...@aol.com> wrote:
>The wire lengths would not drop enough voltage to make any difference. I
Running 4 or 5 of these lamps on a single wire (as they almost always
are!) places a sizable load on that conductor -- figure 5 or 6 amps.
The wire runs are typically 100 feet. Often, 16 AWG wire. Even a
half of a volt can be a sizable drop when you're dealing with 12VDC.
>would suggest that the voltage does make a difference, and that lowering it
>would allow the bulbs to run cooler and longer.
And a "pure DC" supply would also be better -- all else being equal...
You didn't read the entire message, apparently. There are 10 such lamps.
Of these, at least four have been burning without a problem since they
were installed. Of those remaining, some have been cannibalized for
bulbs. Others have burned out *twice* (i.e. this is the third bulb in
some of the fixtures). The effects of any IR losses are questionable
(i.e. the actual voltage at the particular lamps in question) since
I have one lamp at the end of a *6* foot cable that has never need
replacement. Likewise, a lamp at the extreme end of a 100 foot
cable burns without problems. Yet, others seem to burn up overnight!
All lamps are, of course, on at the same time so it's not a question of
service life...
I *strongly* suspect "electrical" causes are NOT the root of the problem!
>> OK, here's the scoop... I've got a bunch of these classy
>>landscape (low voltage) lights here that use small 20W halogen
>>bulbs. They are powered off an (unregulated and probably unfiltered)
>>12VDC (yes, not AC) supply (can you spell "big transformer"?).
>> The problem doesn't appear to be systemic as there are bulbs in the
>>circuit that have been there since day one while others have been
>>replaced twice! Voltages differences don't seem to be a cause,
>>either, (i.e. IR drops in the cables) since some lamps with short runs
>>(i.e. low IR losses) are good while others are bad. Likewise for
>>lamps with *long* runs (high IR losses).
--don
Kellybob1
I had a similar problem with a Halogen lamp... It seems that these bulbs run
hot, and this will damage the lamp socket! I don't kow why, but once the
socket is damaged, you can replace bulbs and they will fail very quickly! I
learned this by trial and error and error and error ( I think about $5 a try!)
. Check your sockets for integrity where the failures have been happening.
It they look corroded, this may be the problem.
Any halogen lamp gurus out there care to educate us on this topic?? Why does a
bad / corroded/ burned socket cause the lamps to fail so fast???
Good luck.
kell...@aol.com
Bob Kelly
Sr. Electrical Design Engineer RF/Video/Analog
San Diego, CA
Don Yuniskis
In article <19970930195...@ladder01.news.aol.com>,
Kellybob1 <kell...@aol.com> wrote:
>I had a similar problem with a Halogen lamp... It seems that these bulbs run
> hot, and this will damage the lamp socket! I don't kow why, but once the
> socket is damaged, you can replace bulbs and they will fail very quickly! I
> learned this by trial and error and error and error ( I think about $5 a try!)
> . Check your sockets for integrity where the failures have been happening.
> It they look corroded, this may be the problem.
Well, I'll take a look. But, there would have to be *several* of these
fixtures having this problem. And it must have started coincident with
their purchase! :>
>Any halogen lamp gurus out there care to educate us on this topic?? Why does a
> bad / corroded/ burned socket cause the lamps to fail so fast???
>Good luck.
Thx!
--don
Don Yuniskis
In article <60rtqo$kqp$1...@news.misty.com>, Don Klipstein <d...@Misty.com> wrote:
>
>Here are my guesses:
>
>1. Weak contact may be dimming the lamps. In some halogen lamps, the
>halogen cycle does not work right if the lamp is dimmed. As somewhat of
>an oversimplification, the halogen cycle may run "backwards" (eat parts of
>the filament and deposit tungsten somewhere on the inner surface of the
>bulb) or "sideways" (eat some parts of the filament and build up other
>parts of the filament).
> I have heard that reverse operation of the halogen cycle should not
>occur, but I believe the slightest contamination by oxygen or water vapor
>can make the bulb require most of full power to work right.
Hmm... kinda leaves you (i.e. *me*!) at the mercy of the socket vendor, then?
>2. The more compact, hotter-running quartz bulbs operate at blazing high
>temperatures and often at high pressure also. You don't want any ash to
>contact red-hot quartz - it could leach into the quartz after several
>hours or dozens of hours, and cause a weak spot or a strained spot in the
>quartz. (Salts also do this, and carbon may make dark spots that could
>overheat by absorbing light.)
Coming from some prior experience with theatrical lighting, rest assured
that the lamps were never "touched" prior to or during installation.
Once installed, they are *almost* hermetically sealed within the fixture.
>3. Poor socket contact may result in bad heating of the socket contacts,
>and this may overheat the base seal of the bulb.
Again, at tthe mercy of the manufacturer...
> Please note that some halogen bulbs (mainly double-ended tubular ones)
>must be operated horizontally. Otherwise, the upper end seal may overheat
>or convection currents may cause the halogen cycle to affect the filament
>unevenly - which can make a thin spot at one end of the filament.
Yes, however those bulbs are usually operated at 110VAC, etc.
These are quite small, "bulb shaped" with both contacts at the bottom.
Oh well... a few more ideas to try!
Thx!
--don
Don Klipstein
Bob Kelly / Kellybob1 (kell...@aol.com) wrote:
: I had a similar problem with a Halogen lamp... It seems that these bulbs run
: hot, and this will damage the lamp socket! I don't kow why, but once the
: socket is damaged, you can replace bulbs and they will fail very quickly! I
:
: Any halogen lamp gurus out there care to educate us on this topic?? Why
: does a bad / corroded/ burned socket cause the lamps to fail so fast???
Here are my guesses:
1. Weak contact may be dimming the lamps. In some halogen lamps, the
halogen cycle does not work right if the lamp is dimmed. As somewhat of
an oversimplification, the halogen cycle may run "backwards" (eat parts of
the filament and deposit tungsten somewhere on the inner surface of the
bulb) or "sideways" (eat some parts of the filament and build up other
parts of the filament).
I have heard that reverse operation of the halogen cycle should not
occur, but I believe the slightest contamination by oxygen or water vapor
can make the bulb require most of full power to work right.
2. The more compact, hotter-running quartz bulbs operate at blazing high
temperatures and often at high pressure also. You don't want any ash to
contact red-hot quartz - it could leach into the quartz after several
hours or dozens of hours, and cause a weak spot or a strained spot in the
quartz. (Salts also do this, and carbon may make dark spots that could
overheat by absorbing light.)
3. Poor socket contact may result in bad heating of the socket contacts,
and this may overheat the base seal of the bulb.
Please note that some halogen bulbs (mainly double-ended tubular ones)
must be operated horizontally. Otherwise, the upper end seal may overheat
or convection currents may cause the halogen cycle to affect the filament
unevenly - which can make a thin spot at one end of the filament.
- Don Klipstein (d...@misty.com)