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OT(maybe): LED Lighting?
Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and
putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? TIA _Chris |
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Chris Stolworthy wrote:
Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? Probably won't work. If you wire them in series any failure kills the whole system. If you put them in parallel the mismatches will steal all the current to a subset. In either case you have to control the actual current. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! |
#3
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"CBFalconer" wrote in message ... Chris Stolworthy wrote: Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? Probably won't work. If you wire them in series any failure kills the whole system. If you put them in parallel the mismatches will steal all the current to a subset. In either case you have to control the actual current. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! Ouch so you mean that I would have to run current to each of them individually if I wanted this to work? Doesn't really sound too feasible to me then. Mostly because I figured that I would need ALOT of LED's to put off much light. Does anyone know how many 10000mcd LED's it would take to equate to say a 60w bulb? |
#4
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"Chris Stolworthy" wrote in message ... Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? although they only take 2 volts or so...and thus safe you'd probably need 1000 or them or more if you used a 5 volt supply, you could put a resistor in series with each one (200 ohms or so) but it seems like a bit too much work to be practical |
#5
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Chris Stolworthy wrote:
"CBFalconer" wrote in message ... Chris Stolworthy wrote: Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? Probably won't work. If you wire them in series any failure kills the whole system. If you put them in parallel the mismatches will steal all the current to a subset. In either case you have to control the actual current. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! Ouch so you mean that I would have to run current to each of them individually if I wanted this to work? Doesn't really sound too feasible to me then. Mostly because I figured that I would need ALOT of LED's to put off much light. Does anyone know how many 10000mcd LED's it would take to equate to say a 60w bulb? There are a lot of LED traffic lights using an array of LEDs. Series/parallel connections work, since the current is controlled by the series resistor(s), and not by any individual LED. I'm sure a traffic signal is a lot brighter than a 60W bulb! Try a Google search. Virg Wall -- A foolish consistency is the hobgoblin of little minds,........ Ralph Waldo Emerson (Microsoft programmer's manual.) |
#6
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"Chris Stolworthy" wrote:
Ok guys I was thinking about taking quite a few of those 10,000mcd LED's and putting them in a steel plate to make a light fixture. My first question is, will this work? Basically what I was thinking is this. Take a sheet of metal and drill holes in it for the LED to stick through, then I could either take a thin piece of wire and run it across all the same polarity contacts on the LED and then run power to those, or maybe just weld the LED's to each other? Anyways after that I would coat them in silicon and put another piece of metal on top to protect them. Kind of sandwiching them. Any thoughts? Also power is a concern of mine, as in how much? And will it be safe? What is the maximum current rating for the LED's you are planning on using, how many LED's will you be using, and at what voltage do you wish to run them at? Jon |
#7
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On Thu, 27 May 2004 10:12:22 -0600, "Chris Stolworthy"
wrote: Probably won't work. If you wire them in series any failure kills the whole system. If you put them in parallel the mismatches will steal all the current to a subset. In either case you have to control the actual current. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! Ouch so you mean that I would have to run current to each of them individually if I wanted this to work? No, that is only necessary if you want a failure of a single LED to only cause that one LED to stop "shining"... ever seen those cheap christmas lights were one goes out and the whole thing does work? Then there are other light strands where one goes out and 1/3 of the set isn't lit, and others where one light goes out and it's only that one light out... same principle, the number of lights in each series dictates how many would go out when one fails, and each series needs it's own current limiter of one form or another (a resistor in the simplest form). It's all a matter of how you design it, how difficult or costly it is to replace one, and the designed and/or expected failure rate. In other words, there's nothing wrong with putting a few in series but it's probably not a good idea to put ALL in series unless the main goal is absolute lowest cost, simplest construction... which many people would scoff at but see the link I provided below, with LEDs @ $0.14 each, and it's not too expensive to just make a few replacement modules and swap them IF necessary. Doesn't really sound too feasible to me then. Mostly because I figured that I would need ALOT of LED's to put off much light. Does anyone know how many 10000mcd LED's it would take to equate to say a 60w bulb? First of all, LEDs are only more efficient than alternatives for spot-lighting, like a flashlight. Fluorescents can be up to (roughly) twice as efficient when wider coverage is needed. Many reports of an LED's great efficiency is ignoring the focused beam, resulting light intensity in measurements, and not investigating (or being able to measure) total light output of a fluorescent easily. The question of how to construct the circuit can depend on a lot of things, like the amount of space, what materials you have, how hard you're driving the LEDs (long long they're expected to last vs. the light output), and the replacement method if/when they fail. If you really wanted to get fancy with this you could also use an LED driver IC, there are quite a few but as an example, http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3756 However, when buying a large quantity of LEDs in bulk there might be no cost effectiveness to using such a driver. Then again, it could matter how small you want this light, since it may be more costly per MCD output to use 10K LEDs than lower MCD value but more LEDs. Likewise, driving them with lower current you'd get lower output at higher cost, but their lifespan may be multiple times higher. In other words, using a 10K MCD LED doesn't _necessarily_ mean that for some designs or uses you'd WANT to get 10K MCD out of one. Superbright LED prices have dropped a lot in the past few years, making it possible that the slight savings in time or support part costs could outweigh the value of having each LED independantly current-limited. You could have 5 parallel sets of 10 in a series, for example, then when one LED goes out you only have that one series out, a 20% light reduction. If you construct this light so it's somewhat modular, you can replace strings of LEDs if necessary, by just plugging in a replacement module, similar to replacing any other light bulb. Then you still have a working light and can investigate which LED in that series failed if you have the inclination to do so, at your leisure. It's not really necessary to use those steel parts you've mentioned. If driving the LEDs hard you may want their leads on soldered to a significant metal (whatever) to 'sink the heat, but that could as easily be a copper-clad PCB as pieces of steel, were're not talking about heatsinks of any external construction, just using the circuit itself as the heatsink is usually sufficient. As for using a 2nd piece of metal to protect the LEDs, it's probably not necessary unless this is going to be mounted on some outdoor, high-velocity vehicle. LEDs are pretty sturdy, relatively speaking. I'll link a couple pictures to give you some ideas, alternatives, whatever... http://www.allelectronics.com/cgi-bi...-16&type=store http://www.allelectronics.com/cgi-bi...S-4&type=store http://www.directleds.com/product_in...products_id=28 |
#8
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"kony" wrote in message ... On Thu, 27 May 2004 10:12:22 -0600, "Chris Stolworthy" wrote: Probably won't work. If you wire them in series any failure kills the whole system. If you put them in parallel the mismatches will steal all the current to a subset. In either case you have to control the actual current. -- Chuck F ) ) Available for consulting/temporary embedded and systems. http://cbfalconer.home.att.net USE worldnet address! Ouch so you mean that I would have to run current to each of them individually if I wanted this to work? No, that is only necessary if you want a failure of a single LED to only cause that one LED to stop "shining"... ever seen those cheap christmas lights were one goes out and the whole thing does work? Then there are other light strands where one goes out and 1/3 of the set isn't lit, and others where one light goes out and it's only that one light out... same principle, the number of lights in each series dictates how many would go out when one fails, and each series needs it's own current limiter of one form or another (a resistor in the simplest form). It's all a matter of how you design it, how difficult or costly it is to replace one, and the designed and/or expected failure rate. In other words, there's nothing wrong with putting a few in series but it's probably not a good idea to put ALL in series unless the main goal is absolute lowest cost, simplest construction... One thing you would have to take in to account is that LED's require a bias voltage to make them work, I think it is about 1/2 a volt but I will look it up as that sounds quite large. Now I am thinking that if they are in series you would have to add the bias voltages togeather so that say 100 leds would require 50volts for them to work!!!. I must admit I am a little unsure about this and possibly once you applied over 1/2 a volt all the LED's would work? Having said that I do go for the former theory where you add the biases togeather. Indeed that is correct. http://www.kpsec.freeuk.com/components/led.htm (very informative page) Also the bias vooltage given there is 2V which is larger than I assumed earlier. Also from http://www.maxim-ic.com/appnotes.cfm...te_number/1883 "LEDs have a MTBF (mean time between failures) usually in the range of 100,000 to over 1,000,000 hours. This is a long time for continuous operation, considering a year is 8760 or 8784 hours. In practice, the useful measure of LED lifetime is its half-life, that is an LED is deemed to have reached the end of its life when the light output falls off to half the original." Also. "Incandescent traffic lamps draw somewhere between 75W and 150W, depending on size (20cm or 30cm) and color (due to differences in the transmissivity of the red, green, and orange filters used). LED traffic lamps draw around 7W - 15W, and can be replaced every 5 years instead of every year for incandescents." So the LED lights require 5 times less maintainance. which many people would scoff at but see the link I provided below, with LEDs @ $0.14 each, and it's not too expensive to just make a few replacement modules and swap them IF necessary. Doesn't really sound too feasible to me then. Mostly because I figured that I would need ALOT of LED's to put off much light. Does anyone know how many 10000mcd LED's it would take to equate to say a 60w bulb? First of all, LEDs are only more efficient than alternatives for spot-lighting, like a flashlight. Fluorescents can be up to (roughly) twice as efficient when wider coverage is needed. Many reports of an LED's great efficiency is ignoring the focused beam, resulting light intensity in measurements, and not investigating (or being able to measure) total light output of a fluorescent easily. The question of how to construct the circuit can depend on a lot of things, like the amount of space, what materials you have, how hard you're driving the LEDs (long long they're expected to last vs. the light output), and the replacement method if/when they fail. If you really wanted to get fancy with this you could also use an LED driver IC, there are quite a few but as an example, http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3756 However, when buying a large quantity of LEDs in bulk there might be no cost effectiveness to using such a driver. Then again, it could matter how small you want this light, since it may be more costly per MCD output to use 10K LEDs than lower MCD value but more LEDs. Likewise, driving them with lower current you'd get lower output at higher cost, but their lifespan may be multiple times higher. In other words, using a 10K MCD LED doesn't _necessarily_ mean that for some designs or uses you'd WANT to get 10K MCD out of one. Superbright LED prices have dropped a lot in the past few years, making it possible that the slight savings in time or support part costs could outweigh the value of having each LED independantly current-limited. You could have 5 parallel sets of 10 in a series, for example, then when one LED goes out you only have that one series out, a 20% light reduction. If you construct this light so it's somewhat modular, you can replace strings of LEDs if necessary, by just plugging in a replacement module, similar to replacing any other light bulb. Then you still have a working light and can investigate which LED in that series failed if you have the inclination to do so, at your leisure. It's not really necessary to use those steel parts you've mentioned. If driving the LEDs hard you may want their leads on soldered to a significant metal (whatever) to 'sink the heat, but that could as easily be a copper-clad PCB as pieces of steel, were're not talking about heatsinks of any external construction, just using the circuit itself as the heatsink is usually sufficient. As for using a 2nd piece of metal to protect the LEDs, it's probably not necessary unless this is going to be mounted on some outdoor, high-velocity vehicle. LEDs are pretty sturdy, relatively speaking. I'll link a couple pictures to give you some ideas, alternatives, whatever... http://www.allelectronics.com/cgi-bi...-16&type=store http://www.allelectronics.com/cgi-bi...S-4&type=store http://www.directleds.com/product_in...products_id=28 |
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