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#1
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LEDs
Just curious...
Has anyone checked out using low voltage white LEDs for lighting in a boat? Is this economically (or otherwise)feasible? I understand that they draw very low voltage/current making them real easy on batteries while providing lots of light. |
#2
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West Marine has a pretty good selection of LED lights.
Doug s/v Callista "sel1" wrote in message ... Just curious... Has anyone checked out using low voltage white LEDs for lighting in a boat? Is this economically (or otherwise)feasible? I understand that they draw very low voltage/current making them real easy on batteries while providing lots of light. |
#3
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Doug Dotson wrote:
West Marine has a pretty good selection of LED lights. Doug s/v Callista "sel1" wrote in message ... Just curious... Has anyone checked out using low voltage white LEDs for lighting in a boat? Is this economically (or otherwise)feasible? I understand that they draw very low voltage/current making them real easy on batteries while providing lots of light. The cheapest source for white LEDs at present seems to be salvage from solar yard lights on sale. OEMs are buying them all up in bulk, I guess, I have not yet seen any at radio shack, or even my parts wholesaler catalogues. Sell your tungsten stocks, solid state lights are here. Soon, they will be a few cents each and plentiful. Each LED consumes about 80 milliamps at 1.6 volts or so. They may be strung in series so that 5 would require 8.1 volts or so to ignite, and require a specific resistor in series in the range of a couple hundreds of ohms to protect the devices from overcurrent, as they cannot protect themselves or control current in the way we usually think with ohm's law, as they have conductive characteristics quite different from resistors, incandescent or otherwise. More like a gas discharge tube, really. You could mix and match red, green and blue to approximate white light. They can be dimmed easily using a rheostat. They are polarised, so require connection in the right direction, anode to positive. Reverse connection means they just don't conduct or light up unless exposed to excessive voltage, in which case they melt and fuse to become an open circuit. They can be driven from an A.C. source, conducting like rectifiers. Yes, they are much more efficient than regular lamps, consuming about 1/10 the power for equivalent light output, but, at the present state of the art, high intensity leds are not really very bright. For low lighting levels, especially low level red night lights, they are ideal. Terry K |
#4
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"Terry Spragg" wrote in message
... Sorry Terry, but your post contains a lot of mis-information. The cheapest source for white LEDs at present seems to be salvage from solar yard lights on sale. OEMs are buying them all up in bulk, I guess, I have not yet seen any at radio shack, or even my parts wholesaler catalogues. White LEDs are commonly available at all major wholesalers. Each LED consumes about 80 milliamps at 1.6 volts or so. No. The voltage drop across a LED depends on the color of the LED. Red LED's drop 1.6V, green and yellow drop appr. 2.0V and blue and white LED's drop around 3.5V. But the voltage is not what you apply. You apply a current, which is 30mA maximum for normal LED's. So, add up all voltages of all leds you have in the string, subtract it from 13V, devide the remaining voltage drop by 0.03 et voila: your resistor value. The white LED Lamps (not LED's) are a different beast. These draw a higher current and are mostly fitted with a current limiting resistor. Never assume a working voltage of these types, always check the datasheet of a specific type. be strung in series so that 5 would require 8.1 volts or so to ignite, and require a specific resistor in series in the range of a couple hundreds of ohms to protect the devices from overcurrent, as they cannot protect themselves or control current in the way we usually think with ohm's law, as they have conductive characteristics quite different from resistors, incandescent or otherwise. More like a gas discharge tube, really. They're just a diode and like all diodes, they will blow if you connect them directly to a voltage source higher than their junction voltage. Reverse connection means they just don't conduct or light up unless exposed to excessive voltage, in which case they melt and fuse to become an open circuit. LED's have a very low reverse breakdown voltage of around 5V. They can be driven from an A.C. source, conducting like rectifiers. No, because of the low breakdown voltage. You can either connect two anti-parallel or of you need only one LED on AC, add a normal diode anti-parallel to conduct during the negative halve of the AC cycle. This way each diode or LED limits the other's reverse voltage to it's own junction voltage. Yes, they are much more efficient than regular lamps, consuming about 1/10 the power for equivalent light output, but, at the present state of the art, high intensity leds are not really very bright. Have you ever stared into a LumiLED without wearing shades...? Meindert |
#5
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So lumens per watt, are they more or less efficient than fluorescents,
including losses in resistors and ballasts? "Meindert Sprang" wrote in message ... "Terry Spragg" wrote in message ... Sorry Terry, but your post contains a lot of mis-information. The cheapest source for white LEDs at present seems to be salvage from solar yard lights on sale. OEMs are buying them all up in bulk, I guess, I have not yet seen any at radio shack, or even my parts wholesaler catalogues. White LEDs are commonly available at all major wholesalers. Each LED consumes about 80 milliamps at 1.6 volts or so. No. The voltage drop across a LED depends on the color of the LED. Red LED's drop 1.6V, green and yellow drop appr. 2.0V and blue and white LED's drop around 3.5V. But the voltage is not what you apply. You apply a current, which is 30mA maximum for normal LED's. So, add up all voltages of all leds you have in the string, subtract it from 13V, devide the remaining voltage drop by 0.03 et voila: your resistor value. The white LED Lamps (not LED's) are a different beast. These draw a higher current and are mostly fitted with a current limiting resistor. Never assume a working voltage of these types, always check the datasheet of a specific type. be strung in series so that 5 would require 8.1 volts or so to ignite, and require a specific resistor in series in the range of a couple hundreds of ohms to protect the devices from overcurrent, as they cannot protect themselves or control current in the way we usually think with ohm's law, as they have conductive characteristics quite different from resistors, incandescent or otherwise. More like a gas discharge tube, really. They're just a diode and like all diodes, they will blow if you connect them directly to a voltage source higher than their junction voltage. Reverse connection means they just don't conduct or light up unless exposed to excessive voltage, in which case they melt and fuse to become an open circuit. LED's have a very low reverse breakdown voltage of around 5V. They can be driven from an A.C. source, conducting like rectifiers. No, because of the low breakdown voltage. You can either connect two anti-parallel or of you need only one LED on AC, add a normal diode anti-parallel to conduct during the negative halve of the AC cycle. This way each diode or LED limits the other's reverse voltage to it's own junction voltage. Yes, they are much more efficient than regular lamps, consuming about 1/10 the power for equivalent light output, but, at the present state of the art, high intensity leds are not really very bright. Have you ever stared into a LumiLED without wearing shades...? Meindert |
#6
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First: My opinion is that regular "white" LEDs are really too blue to use as
the only overhead lighting. Did a comparison on "warm white" LEDs from Luxeon and halogen light bulbs from Osram. There are no warm white leds giving more lumens/watt than the halogen light, at the best they are equal. On the other hand a "warm white" LED is probably 50 times more expensive than the halogen. And this did not take into account that one needs a resistor in series or some type of switching supply. And flourecent lights are much more efficien than halogens. There are no CE marked LED navigation lights for boats larger than 12m, wonder why? Regs/TomS "Steve Alexanderson" Idon'tlikegreeneggsandspamIdon'tlikethemsamIamsal wrote in message ... So lumens per watt, are they more or less efficient than fluorescents, including losses in resistors and ballasts? "Meindert Sprang" wrote in message ... "Terry Spragg" wrote in message ... Sorry Terry, but your post contains a lot of mis-information. The cheapest source for white LEDs at present seems to be salvage from solar yard lights on sale. OEMs are buying them all up in bulk, I guess, I have not yet seen any at radio shack, or even my parts wholesaler catalogues. White LEDs are commonly available at all major wholesalers. Each LED consumes about 80 milliamps at 1.6 volts or so. No. The voltage drop across a LED depends on the color of the LED. Red LED's drop 1.6V, green and yellow drop appr. 2.0V and blue and white LED's drop around 3.5V. But the voltage is not what you apply. You apply a current, which is 30mA maximum for normal LED's. So, add up all voltages of all leds you have in the string, subtract it from 13V, devide the remaining voltage drop by 0.03 et voila: your resistor value. The white LED Lamps (not LED's) are a different beast. These draw a higher current and are mostly fitted with a current limiting resistor. Never assume a working voltage of these types, always check the datasheet of a specific type. be strung in series so that 5 would require 8.1 volts or so to ignite, and require a specific resistor in series in the range of a couple hundreds of ohms to protect the devices from overcurrent, as they cannot protect themselves or control current in the way we usually think with ohm's law, as they have conductive characteristics quite different from resistors, incandescent or otherwise. More like a gas discharge tube, really. They're just a diode and like all diodes, they will blow if you connect them directly to a voltage source higher than their junction voltage. Reverse connection means they just don't conduct or light up unless exposed to excessive voltage, in which case they melt and fuse to become an open circuit. LED's have a very low reverse breakdown voltage of around 5V. They can be driven from an A.C. source, conducting like rectifiers. No, because of the low breakdown voltage. You can either connect two anti-parallel or of you need only one LED on AC, add a normal diode anti-parallel to conduct during the negative halve of the AC cycle. This way each diode or LED limits the other's reverse voltage to it's own junction voltage. Yes, they are much more efficient than regular lamps, consuming about 1/10 the power for equivalent light output, but, at the present state of the art, high intensity leds are not really very bright. Have you ever stared into a LumiLED without wearing shades...? Meindert |
#7
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Like most postings, it draws varying opinions, but gets you thinking. At the
risk of asking a dumb question, you refer to "white LED Lamps (not LED's) are a different beast." What do you mean by LED Lamps. If they are a different beast, what are they? "Meindert Sprang" wrote in message ... "Terry Spragg" wrote in message ... Sorry Terry, but your post contains a lot of mis-information. The cheapest source for white LEDs at present seems to be salvage from solar yard lights on sale. OEMs are buying them all up in bulk, I guess, I have not yet seen any at radio shack, or even my parts wholesaler catalogues. White LEDs are commonly available at all major wholesalers. Each LED consumes about 80 milliamps at 1.6 volts or so. No. The voltage drop across a LED depends on the color of the LED. Red LED's drop 1.6V, green and yellow drop appr. 2.0V and blue and white LED's drop around 3.5V. But the voltage is not what you apply. You apply a current, which is 30mA maximum for normal LED's. So, add up all voltages of all leds you have in the string, subtract it from 13V, devide the remaining voltage drop by 0.03 et voila: your resistor value. The white LED Lamps (not LED's) are a different beast. These draw a higher current and are mostly fitted with a current limiting resistor. Never assume a working voltage of these types, always check the datasheet of a specific type. be strung in series so that 5 would require 8.1 volts or so to ignite, and require a specific resistor in series in the range of a couple hundreds of ohms to protect the devices from overcurrent, as they cannot protect themselves or control current in the way we usually think with ohm's law, as they have conductive characteristics quite different from resistors, incandescent or otherwise. More like a gas discharge tube, really. They're just a diode and like all diodes, they will blow if you connect them directly to a voltage source higher than their junction voltage. Reverse connection means they just don't conduct or light up unless exposed to excessive voltage, in which case they melt and fuse to become an open circuit. LED's have a very low reverse breakdown voltage of around 5V. They can be driven from an A.C. source, conducting like rectifiers. No, because of the low breakdown voltage. You can either connect two anti-parallel or of you need only one LED on AC, add a normal diode anti-parallel to conduct during the negative halve of the AC cycle. This way each diode or LED limits the other's reverse voltage to it's own junction voltage. Yes, they are much more efficient than regular lamps, consuming about 1/10 the power for equivalent light output, but, at the present state of the art, high intensity leds are not really very bright. Have you ever stared into a LumiLED without wearing shades...? Meindert |
#8
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"sel1" wrote in message
... Like most postings, it draws varying opinions, but gets you thinking. At the risk of asking a dumb question, you refer to "white LED Lamps (not LED's) are a different beast." What do you mean by LED Lamps. If they are a different beast, what are they? LED lamps are mostly one or more LED chips on a substrate, with a suitable current-limiting resistor to make them suitable for a normalized voltage like 5V or 12V Meindert |
#9
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Terry Spragg wrote:
removed Each LED consumes about 80 milliamps at 1.6 volts or so. I think you're mistaken here. If I remember correctly, most LED's require a minimum voltage of 1.7v just to conduct current across the diode. (Someone help me here if my terminology is incorrect as well as my lack of electronics knowledge.) You would have a hard time seeing an LED running at that low of a voltage. I believe most white LED's require a minimum voltage of 3.6 volts, at least all of the ones I've dealt with. Sometimes they are driven at a higher than rated voltage to get more or rather brighter light, as in some flashlights, but the LED's that are overdriven like this will typically be heatsinked(sp?). If anyone is looking for a reasonably priced supplier in the US, check out superbrightleds.com. They seem to have some of the brightest LED's and their prices are, or at least were, the best I've found for LED's. They also have LED lamps. -Jim |
#10
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I've seen quite a number of White LED driver chips on the market.
Apparently they are boost converters that output 32 volts to drive 2 to 8 LEDs from a 3.3 to 5.5V supply. Apparently the flash in my cellphone camera is a white LED. Doug s/v Callista "Jim" wrote in message ... Terry Spragg wrote: removed Each LED consumes about 80 milliamps at 1.6 volts or so. I think you're mistaken here. If I remember correctly, most LED's require a minimum voltage of 1.7v just to conduct current across the diode. (Someone help me here if my terminology is incorrect as well as my lack of electronics knowledge.) You would have a hard time seeing an LED running at that low of a voltage. I believe most white LED's require a minimum voltage of 3.6 volts, at least all of the ones I've dealt with. Sometimes they are driven at a higher than rated voltage to get more or rather brighter light, as in some flashlights, but the LED's that are overdriven like this will typically be heatsinked(sp?). If anyone is looking for a reasonably priced supplier in the US, check out superbrightleds.com. They seem to have some of the brightest LED's and their prices are, or at least were, the best I've found for LED's. They also have LED lamps. -Jim |
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