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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... |
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. |
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 |
"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 |
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