|
Lamps?
Looking for tiny incandescent lamps for my TM-451A Kenwood.
Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? Bob |
Bob wrote:
Looking for tiny incandescent lamps for my TM-451A Kenwood. Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? Bob Could they be 5 volts? If so, Mouser has some lamps with wire leads and ..094 diameter bulb. Search p/n 6833 and 7153. -Bill M |
Bob wrote:
Looking for tiny incandescent lamps for my TM-451A Kenwood. You might try a model train shop. The ones catering to people who build their own locomotives have small bulbs of various voltages, though 1.5 and 12 volt are the most common. Prices range from $1 to $3 per bulb. |
Looking for tiny incandescent lamps for my TM-451A Kenwood. Have you considered putting in a small clear LED with limiting resister to the 6 volts? I've done this. Never have to replace a bulb again. Ed |
Bob wrote:
Looking for tiny incandescent lamps for my TM-451A Kenwood. Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? The 272-1140 6V lamp from Radio Shark should work, if they still stock it. Bob |
James Robinson wrote:
Bob wrote: Looking for tiny incandescent lamps for my TM-451A Kenwood. You might try a model train shop. The ones catering to people who build their own locomotives have small bulbs of various voltages, though 1.5 and 12 volt are the most common. Prices range from $1 to $3 per bulb. One thing that you should already realize is that the new ones will eventually burn out, too. So it would be wise to do the right thing and replace them with LEDs, and they will last tens of thousands of hours. |
Lizard Blizzard wrote: James Robinson wrote: Bob wrote: Looking for tiny incandescent lamps for my TM-451A Kenwood. You might try a model train shop. The ones catering to people who build their own locomotives have small bulbs of various voltages, though 1.5 and 12 volt are the most common. Prices range from $1 to $3 per bulb. One thing that you should already realize is that the new ones will eventually burn out, too. So it would be wise to do the right thing and replace them with LEDs, and they will last tens of thousands of hours. I do that routinely at the shop where I work on TAD M-8's and MD-150's, which use a similar scheme. However, you have to be sure to add appropriate limiting resistors for each series string! Cheers, Fred -- +--------------------------------------------+ | Music: http://www3.telus.net/dogstarmusic/ | | Projects, Vacuum Tubes & other stuff: | | http://www.dogstar.dantimax.dk | +--------------------------------------------+ |
I have searched many of the usual sources and can't seem to locate
replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? ======== Suggest you have a look at QST -Sep 2003 , page 38 . There you find an article : Solid-State Those Pilot Lamps , by AD5X Since your bulbs have wire leads you can readily replace them by a LED (of your desired coulour) and an appropriate resistor. After that you can forget about replacement for ever . Good Luck Frank GM0CSZ / KN6WH |
In article , Lizard Blizzard wrote:
eventually burn out, too. So it would be wise to do the right thing and replace them with LEDs, and they will last tens of thousands of hours. I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from Radio Shack. The supply voltage is 5 volts so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Are there any 5 volt LEDs around? -- Sven Weil New York City, U.S.A. |
Sven Franklyn Weil wrote: In article , Lizard Blizzard wrote: eventually burn out, too. So it would be wise to do the right thing and replace them with LEDs, and they will last tens of thousands of hours. I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from Radio Shack. The supply voltage is 5 volts so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Are there any 5 volt LEDs around? Any LED can be a 5 volt LED with an appropriate dropping resistor. ;-) That being said, there *is* an LED rated for operation directly from a 5 volt line. Unfortunately, it's a flasher. Cheers, Fred -- +--------------------------------------------+ | Music: http://www3.telus.net/dogstarmusic/ | | Projects, Vacuum Tubes & other stuff: | | http://www.dogstar.dantimax.dk | +--------------------------------------------+ |
"Fred Nachbaur" wrote in message
news:xe33b.61864$K44.43700@edtnps84... That being said, there *is* an LED rated for operation directly from a 5 volt line. Unfortunately, it's a flasher. Either blue or while LEDs have pretty high voltage. Of course, they require current limiting, which requires an overhead of voltage... Tim -- In the immortal words of Ned Flanders: "No foot longs!" Website @ http://webpages.charter.net/dawill/tmoranwms |
To all who suggested LEDs, thanks for the suggestions but there is a
problem. These are not pilot lamps. They illuminate an LCD and need to be controllable by a regulator circuit for intensity. LEDs aren't really suited to this application, although some modification of the circuitry and optics might make it work. All I want to do is get some more incandescent lamps for this radio, and keep it close to original. Bob |
Lizard Blizzard wrote:
Bob wrote: Looking for tiny incandescent lamps for my TM-451A Kenwood. Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? The 272-1140 6V lamp from Radio Shark should work, if they still stock it. They have them. I just bought a pack a few weeks ago. - Mike KB3EIA - |
"Sven Franklyn Weil" wrote in message
... In article , Lizard Blizzard wrote: Are there any 5 volt LEDs around? Indeed there are. Check for panel lights or LED panel illuminators in any good electronics catalog- they come in lamp style mounts. The units have multiple dice inside and the proper dropping resistor in place already. Cheers! Chip Shults My robotics, space and CGI web page - http://home.cfl.rr.com/aichip |
Bob wrote: All I want to do is get some more incandescent lamps for this radio, and keep it close to original. email JKL Lamps and ask what they've got to meet your specs. If they don't have it - you're in trouble- they have several THOUSAND types available. You do have to go through one of their distributors - but they'll tell you who has the lamp you want. You're going to need to measure the bulb very carefully length & diameter - is it round or cylindrical; wires out the bottom (standard) or each end (axial)... and you're going to need the voltage and current of one bulb. JKL has wire base bulbs in 5 and 6 volts from T-3/4 size (.187 Long X ..094 diameter( to T-1 3/4 (.520 long X .230 diameter)... the T-1 1/4 standard size come in 5V @21, 40, 60, 75, 115ma - 6V @ 40, 60, 200ma 6.3V @70 & 200ma - life ave 10,000 - 100,000 This is the bunch that the has "fuse clip" bulbs in 6.3, 8 and 12V email: best regards... -- randy guttery A Tender Tale - a page dedicated to those Ships and Crews so vital to the United States Silent Service: http://tendertale.com |
Sven Franklyn Weil wrote:
In article , Lizard Blizzard wrote: eventually burn out, too. So it would be wise to do the right thing and replace them with LEDs, and they will last tens of thousands of hours. I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from Radio Shack. The supply voltage is 5 volts so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs myself.... |
But the light output goes down with at least as strong a function, I
believe. So although you can greatly extend the life of a bulb by reducing the voltage, you also greatly reduce the light output. And without nearly as much of a reduction of the input power. So you end up with a dim, very inefficient bulb. That might be ok for some applications (say, if it's at the top of a tower where it's a really major pain to change) but not others (like all the bulbs in your house, unless you love to pay that electric bill). Roy Lewallen, W7EL Robert Casey wrote: Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs myself.... |
In article , Robert Casey wrote:
Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs myself.... Rob, I'm probably being dense but I don't follow the math. Then again I was never really good at math. what is the ^6? Elevated to the 6th power? So is this bulb going to last a while? P.S.: If it blows in my lifetime I'm not replacing it again. The only reason I did so the first time was because the original had blown its glass envelope (I _don't_ know why). Yikes!! -- Sven Weil New York City, U.S.A. |
Sven Franklyn Weil wrote:
In article , Robert Casey wrote: Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs myself.... Rob, I'm probably being dense but I don't follow the math. Then again I was never really good at math. what is the ^6? Elevated to the 6th power? So is this bulb going to last a while? That's right. P.S.: If it blows in my lifetime I'm not replacing it again. The only reason I did so the first time was because the original had blown its glass envelope (I _don't_ know why). Yikes!! |
my recollection of the equation for life as a function of voltage is that
it's the 13th power, not 6th. - unfortunately, I can't find the GE lighting handbook I got this out of to confirm. by the way, if anyone wants some optoelectronics catalogs from the early 70s, contact me off the list snip Imagine my surprise when these damned things are only rated for 15 hours!!!! Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs myself.... |
I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from
Radio Shack. The supply voltage is 5 volts, so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs... I was going to post something on this, but refrained. However... Many years ago, when transistor amplifiers were still new and exotic, Allied introduced the KG-870, an integrated amp using germanium alloy transistors (you know, the ones that barely got past 5kHz). At that time, a lot of attention was paid to protecting the output devices. (Germanium transistors were prone to thermal runaway.) Allied had an interesting solution -- the emitter resistors were actually 12V automotive lamps! If "too much" current passed through the transistor, the bulb's resistance would increase, restraining the flow. The bulb was also supposed to be a fuse. The writer of the Electronics World article explained that the life of a tungsten lamp varied as the 12th power of the applied voltage. Get the voltage high enough, and the lifetime becomes a fraction of a second. He didn't say where he got the 12th-power rule. Anybody know? |
In article , Robert Casey wrote:
That's right. Awesome! I like the sound of that!! :-) Thanks. I assumed that if since it was rated for 15 hours that it would last for 30 hours if run at approx half the rated volts. -- Sven Weil New York City, U.S.A. |
I found graphs in a 1978 GE miniature lamp data book, giving life,
candlepower, and current as a function of lamp voltage. It has a bunch of qualifications: "Calculations of characteristics shown in Chart I are approximate only between 95% and 110% of rated voltage for lamp types with 5,000 hours life or less. Certain lamp types will vary widely from calculated values. This chart will not apply to lamps with lives in excess of 5,000 hours. This chart does not apply to halogen cycle lamps." It extends from 60% to 140% of rated voltage. The text accompanying the graph says that, "as approximations", the light output varies as the 3.6 power of the voltage and the life varies inversely as the 12th power of the voltage. It also says of the graphs that "Indicated values (except for long life lamps) are reasonably valid, between 95% and 110% rated volts. Beyond that, indicated characteristics may not be realized because of the increasing influence of factors which cannot be incorporated into the chart." I assume that long life bulbs are excluded because they're already running a a considerably lower than "normal" voltage. At 60% of rated voltage, the graphs show that the current had decreased to about 75% of rated current, while the candlepower has dropped to something like 17% of rated output. (This means the efficiency is around 38% of normal.) Life is around 650 times the rated life. In the other direction, at 140% of rated voltage, you get about 120% of rated current, about 325% normal brightness, and about 0.016 times normal life. "Double life" bulbs are popular. You can make any bulb into a "double life" bulb (according to the graphs) by running it at 95% of normal voltage. Current will drop 3 or 4 percent, and you'll get about 85% of normal light output. I'm sure more information is available on the web for anyone who's interested. Roy Lewallen, W7EL |
030827 1317 - Al wrote:
There's never enough time to do it right the first time....... Or: There's never enough time to do it right, but there's always enough time to do it over... |
Thanks for the confirmation of 12th power.
It extends from 60% to 140% of rated voltage. The text accompanying the graph says that, "as approximations", the light output varies as the 3.6 power of the voltage and the life varies inversely as the 12th power of the voltage. It also says of the graphs that "Indicated values (except for long life lamps) are reasonably valid, between 95% and 110% rated volts. Beyond that, indicated characteristics may not be realized because of the increasing influence of factors which cannot be incorporated into the chart." I assume that long life bulbs are excluded because they're already running a a considerably lower than "normal" voltage. At 60% of rated voltage, the graphs show that the current had decreased to about 75% of rated current, while the candlepower has dropped to something like 17% of rated output. (This means the efficiency is around 38% of normal.) Life is around 650 times the rated life. |
In article ,
mentioned... I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from Radio Shack. The supply voltage is 5 volts, so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs... I was going to post something on this, but refrained. However... [snip] He didn't say where he got the 12th-power rule. Anybody know? Well, the GE mini lamp catalog mentions this, and GE has been around since day 1, so I would guess that they came up with the figure. -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ |
"Roy Lewallen" wrote in message ... I found graphs in a 1978 GE miniature lamp data book, giving life, candlepower, and current as a function of lamp voltage. It has a bunch of qualifications: "Calculations of characteristics shown in Chart I are approximate only between 95% and 110% of rated voltage for lamp types with 5,000 hours life or less. Certain lamp types will vary widely from calculated values. This chart will not apply to lamps with lives in excess of 5,000 hours. This chart does not apply to halogen cycle lamps." It extends from 60% to 140% of rated voltage. The text accompanying the graph says that, "as approximations", the light output varies as the 3.6 power of the voltage and the life varies inversely as the 12th power of the voltage. It also says of the graphs that "Indicated values (except for long life lamps) are reasonably valid, between 95% and 110% rated volts. Beyond that, indicated characteristics may not be realized because of the increasing influence of factors which cannot be incorporated into the chart." I assume that long life bulbs are excluded because they're already running a a considerably lower than "normal" voltage. At 60% of rated voltage, the graphs show that the current had decreased to about 75% of rated current, while the candlepower has dropped to something like 17% of rated output. (This means the efficiency is around 38% of normal.) Life is around 650 times the rated life. In the other direction, at 140% of rated voltage, you get about 120% of rated current, about 325% normal brightness, and about 0.016 times normal life. "Double life" bulbs are popular. You can make any bulb into a "double life" bulb (according to the graphs) by running it at 95% of normal voltage. Current will drop 3 or 4 percent, and you'll get about 85% of normal light output. I'm sure more information is available on the web for anyone who's interested. Roy Lewallen, W7EL Running a lamp undervoltage sure does work. I put 220 volt bulbs in a 110v porch light. Bright enough to see ok and they have lasted for 8 years now being on nearly every night! I don't care if I get as lumens per watt as the house next door. It works! Ghost |
"William Sommerwerck" wrote in message ... I replaced a grain-of-wheat lightbulb for a clock-radio dial with one from Radio Shack. The supply voltage is 5 volts, so I bought a 12 volt bulb. Imagine my surprise when these damned things are only rated for 15 hours!!!! Well, the life of a bulb is roughly (rated voltage/operating voltage)^6 so (12/5)^6= 191 * 15 hours = 2865 hours. I'd call these 5V bulbs... I was going to post something on this, but refrained. However... Many years ago, when transistor amplifiers were still new and exotic, Allied introduced the KG-870, an integrated amp using germanium alloy transistors (you know, the ones that barely got past 5kHz). At that time, a lot of attention was paid to protecting the output devices. (Germanium transistors were prone to thermal runaway.) Allied had an interesting solution -- the emitter resistors were actually 12V automotive lamps! If "too much" current passed through the transistor, the bulb's resistance would increase, restraining the flow. The bulb was also supposed to be a fuse. The writer of the Electronics World article explained that the life of a tungsten lamp varied as the 12th power of the applied voltage. Get the voltage high enough, and the lifetime becomes a fraction of a second. He didn't say where he got the 12th-power rule. Anybody know? Lamps and PTC thermisters are used as non-linear resistors. The diode knee is also very non-linear. Lamps are sometimes used in the feedback loop or good clean sine wave oscillators. They stabilize around the non-linearity. Ghost |
Bob wrote:
Looking for tiny incandescent lamps for my TM-451A Kenwood. Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? Bob Perhaps one of these might fit the bill, LED replacements for typical incandesents... http://dkc3.digikey.com/PDF/T033/1200.pdf |
In article ,
"Mark Jones" 127.0.0.1 wrote: Bob wrote: Looking for tiny incandescent lamps for my TM-451A Kenwood. Apparently these are 6 V or so; there are four of them in series parallel controlled by a regulator to vary intensity. They light up the LCD and two of them are burned out. I have searched many of the usual sources and can't seem to locate replacement lamps; as a last resort I could go to Pacific Parts but they are so expensive. These are just inexpensively made tiny bulbs with wire leads. Any suggestions? Bob Perhaps one of these might fit the bill, LED replacements for typical incandesents... http://dkc3.digikey.com/PDF/T033/1200.pdf You seem fixated on replacing the originals with incadescent bulbs. Here is another source: http://www.lightbulbwarehouse.com/ And if that is too expensive, try the miniature bulbs used for model trains or doll houses or christmas tree lights. Al -- There's never enough time to do it right the first time....... |
William Sommerwerck wrote: He didn't say where he got the 12th-power rule. Anybody know? I don't know where it came from, or if it is accurate. (I don't doubt or dispute it - I just don't know.) But in 1978 I wired the 2 bulbs in the each of the EXIT lights in the church in series. They were burning out in 3-4 months before that. Since I wired them in series, we haven't had to replace a single bulb. The bulbs are lit 24x7, so they don't go through any on/off stress. |
On Thu, 28 Aug 2003 12:44:54 -0700, the renowned "William Sommerwerck"
wrote: Thanks for the confirmation of 12th power. The 12th power approximation does originate at GE Lighting, AFAIK, but is only valid for voltages rather close to the rated operating voltage, and for typical high voltage incandescent lamps. Long-life and halogen bulbs WON'T behave the same. http://www.eaoswitch.com/about/lamps.htm Here's a rule of thumb for low-voltage halogens: http://www.ndlight.com.au/low_voltage_lighting.htm They claim a 5% voltage increase will reduce life by 50%, which is more like the 13.5th power. The one time I checked the 12th power approximation against actual testing of low wattage high voltage (mains) lamps it was off by more than an order of magnitude, so take the whole thing with a grain of salt, IMHO, unless your lamp type matches the type used for testing. I'm sure a real lamp specialist could go on for hours about this sort of thing. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
The 12th power approximation does originate at GE Lighting,
AFAIK, but is only valid for voltages rather close to the rated operating voltage, and for typical high voltage incandescent lamps. Long-life and halogen bulbs WON'T behave the same. The urban legend about halogen lamps is that reducing the voltage even slightly causes the filament to burn out prematurely. The reasoning is that the slight drop in temperature reduces the halogen self-healing effect much more than it reduces the evaporation of the filament. I believe this is correct. Thanks for the references. Now... Does anyone know anything about helium reducing the life of incandescent lamps? grin http://www.eaoswitch.com/about/lamps.htm Here's a rule of thumb for low-voltage halogens: http://www.ndlight.com.au/low_voltage_lighting.htm They claim a 5% voltage increase will reduce life by 50%, which is more like the 13.5th power. The one time I checked the 12th power approximation against actual testing of low wattage high voltage (mains) lamps it was off by more than an order of magnitude, so take the whole thing with a grain of salt, IMHO, unless your lamp type matches the type used for testing. I'm sure a real lamp specialist could go on for hours about this sort of thing. |
On Sun, 31 Aug 2003 10:38:58 GMT, Spehro Pefhany
wrote: On Thu, 28 Aug 2003 12:44:54 -0700, the renowned "William Sommerwerck" wrote: Thanks for the confirmation of 12th power. The 12th power approximation does originate at GE Lighting, AFAIK, but is only valid for voltages rather close to the rated operating voltage, and for typical high voltage incandescent lamps. Long-life and halogen bulbs WON'T behave the same. http://www.eaoswitch.com/about/lamps.htm Here's a rule of thumb for low-voltage halogens: http://www.ndlight.com.au/low_voltage_lighting.htm The problem with Halogens is LOW voltage reduces the life of the bulb as well. The Halogen Cycle requires a minimum temperature in order to re-deposit the tungsten on the filament.Low voltage boils the tungsten off and deposits it on the glass envelope. Eventually the glass gets dark and the filament gets too thin and burns out. Specified voltage maintains proper temperature for thr reddepositing of tungsten on the filament. This operating heat is why quartz glass envelopes are generally used for halogen bulbs. This is copied from elsewhere on the web: What is the difference between the internal conditions and mass transports happening inside the noble gas fill, and the halogen cycle incandescent bulbs? Noble gases do not react with the tungsten vapor, leading to a layer of semi-opaque condensed tungsten on the inner surface of the bulb. Since the bulb is cooler than the boiling point of tungsten, tungsten is gradually transfered from the filament to the bulb until the filament burns out. Halogens react with tungsten vapor, resulting in a layer of tungsten halide on the inner surface of the bulb --- but since tungsten halide is transparent, less light is absorbed. Also, tungsten halide has a low enough boiling point that it can re-evaporate when the bulb is hot enough. Finally, if tungsten halide molecules get close enough to the fillament, they can disassociate back into tungsten and halogen atoms, and the tungsten can be re-deposited onto the filament, extending its lifetime, while the halogen goes back into the fill gas. There is an important elegance to the tungsten-halogen cycle. Because the filament is a series resistance with a positive temperature coefficient of resistance, any part that thins by sublimation runs hotter than the rest. In a conventional bulb the heavy gas fill acts to reduce sublimation and thermally insulate the filament so a given power level gives more visible light. However, a localized thinning gives positive feedback and failure. In a tungsten-halogen bulb, sublimated tungsten reacts to give volatile tungsten halides that thermally decompose and redeposit metal at the hottest spots. The bulb does not darken from transported tungsten. The hottest spots get rebuilt. Negative feedback allows a filament to be run very hot indeed. There is a price to be paid. The envelope must be made of fused silica to take the high temperature. A mere trace of sodium (a fingerprint) catalyzes crystallization of fused slica to cristobalite at temp. When the envelope cools or heats it cracks from differential coefficients of thermal expansion. When tungsten halogen bulbs fail in use the results are often quite... attention-getting. Internal pressure at operating temperature can be several atmospheres. Tungsten halogen bulbs also have a pretty good UV component compared to ordinary incandescents unless the envelope is doped with cerium or such. |
|
nobody wrote: In wrote: But in 1978 I wired the 2 bulbs in the each of the EXIT lights in the church in series. Congratulations, you probably bypassed a safety feature. If they're in parallel, if one burns out the other keeps going. In series, if one goes they're both out, and the exit sign is no longer visible. But if he'd have left them in parallel, they most certainly would have both burned out long ago! :-p Cheers, Fred -- +--------------------------------------------+ | Music: http://www3.telus.net/dogstarmusic/ | | Projects: http://dogstar.dantimax.dk | +--------------------------------------------+ |
A diode, ballast, or capacitor in series with each lamp would be
fairly good too. Ballast is best because it performs surge suppression. Stepan On Tue, 02 Sep 2003 21:04:55 GMT, Fred Nachbaur wrote: nobody wrote: In wrote: But in 1978 I wired the 2 bulbs in the each of the EXIT lights in the church in series. Congratulations, you probably bypassed a safety feature. If they're in parallel, if one burns out the other keeps going. In series, if one goes they're both out, and the exit sign is no longer visible. But if he'd have left them in parallel, they most certainly would have both burned out long ago! :-p Cheers, Fred |
On 2 Sep 2003 20:44:40 GMT, nobody wrote:
In wrote: But in 1978 I wired the 2 bulbs in the each of the EXIT lights in the church in series. Congratulations, you probably bypassed a safety feature. If they're in parallel, if one burns out the other keeps going. In series, if one goes they're both out, and the exit sign is no longer visible. And what if both burn out in parallel, which they eventually will - and eventually is measured in months or, at best a low number of years. With the series string, if one blows it will likely be a decade or 2 or 3. |
In article , Stepan
Novotill wrote: A diode, ballast, or capacitor in series with each lamp would be That would have been the proper solution. There are these little buttons you stick to the tip of the screw-base of the bulb. You then screw this entire thing into the socket. It's called a "bulb saver" and is essentially a tiny diode in series that chops the voltage across the bulb in half. I assume the bulb bases for these exit lights are much smaller than Edison based household bulbs (intermediate base perhaps?) and the bulb savers I've seen are only for Edison sockets. I think some EXIT lamp manufacturers were also selling LED retrofit kits for some of these lights. Also, door slamming and vibration could have been a partial reason for premature lamp failure. But now we're getting WAAYYYYYY off topic here. -- Sven Weil New York City, U.S.A. |
| All times are GMT +1. The time now is 05:05 PM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
RadioBanter.com