I have a couple of rather unique applications that I am attempting to develop LED light bulbs for and I'm hoping that someone here might be able to help guide me in the right direction.
With the phase out of incandescent light bulbs quite a few historic preservation groups are finding that the light bulbs used in their old equipment are simply no longer available. I've had some sample bulbs produced by a manufacturer in China and they failed miserably (sometimes explosively) when we tried them out. The power source for the application I am working on is a 1000W 34V DC steam powered dynamo with a 30 A output. The dyamo feeds into a breaker box which feeds several circuits. We run about 15 or so 15W 34V DC light bulbs (0.5 A each) on one of those circuits. I am looking to replace those bulbs with LED and this is where I've hit a road block. The Chinese manufacturer upgraded some of the components of the driver (40V for the IC, 50V for the capacitor) but as I said they simply didn't last. The dynamo speed (and hence voltage, etc) can swing pretty wildly and when we hit 42V the bulb failed pretty spectacularly.
I have a number of components for the bulb and am going to try to figure this out on my own but I'm going in circles at this point. I've identified a driver (NSI50350ADT4G from ON Semiconductor http://www.onsemi.com/pub_link/Collateral/NSI50350AD-D.PDF) that I think will work just fine for this application and I've mocked up a bulb but the LEDs burned out as soon as I connected the power supply. I have a benchtop power supply (34-40V DC, 350W, 9.7A) that I use to test the mock-ups. The bulbs themselves are made of 8 separate boards with six 3528 SMD LEDs. I found a spec sheet that tells that the 3528 LEDs have a forward voltage of about 3.3V, forward current of 60mA, and dissipate 200mW. I'm not 100% sure but it seems the bulbs are wired as 8 parallel boards, with the six individual LEDs in series. I've attached a circuit diagram and I'm thinking I need to just find the right size resistor to make it work. If so, what size resistor do I need? I've done the math several times and I don't get the same answer twice. What am I doing wrong? What wattage would the resistor need to be?
As a separate question closely related, I purchased a handful of 30W high power LEDs for a different style bulb running off the same power source. The bulb to be replaced is a 250W bulb and I will need 4 of the 30W LEDs to give the same amount of light. I can't even light two of these LEDs in series and before I try wiring them in parallel I need some advice on that as well. These LEDs operate on 32-34V DC and the limited info that I can find indicates a forward current of 1000mA and that the forward voltage is the same as the input voltage. I don't know if it's a bad translation or if the forward voltage is indeed the same as the input but that seems very suspicious to me. Does anyone have any thoughts on that? If wiring in parallel is the way to go, what size resistor would I need in that case.
Appreciate the help!
With the phase out of incandescent light bulbs quite a few historic preservation groups are finding that the light bulbs used in their old equipment are simply no longer available. I've had some sample bulbs produced by a manufacturer in China and they failed miserably (sometimes explosively) when we tried them out. The power source for the application I am working on is a 1000W 34V DC steam powered dynamo with a 30 A output. The dyamo feeds into a breaker box which feeds several circuits. We run about 15 or so 15W 34V DC light bulbs (0.5 A each) on one of those circuits. I am looking to replace those bulbs with LED and this is where I've hit a road block. The Chinese manufacturer upgraded some of the components of the driver (40V for the IC, 50V for the capacitor) but as I said they simply didn't last. The dynamo speed (and hence voltage, etc) can swing pretty wildly and when we hit 42V the bulb failed pretty spectacularly.
I have a number of components for the bulb and am going to try to figure this out on my own but I'm going in circles at this point. I've identified a driver (NSI50350ADT4G from ON Semiconductor http://www.onsemi.com/pub_link/Collateral/NSI50350AD-D.PDF) that I think will work just fine for this application and I've mocked up a bulb but the LEDs burned out as soon as I connected the power supply. I have a benchtop power supply (34-40V DC, 350W, 9.7A) that I use to test the mock-ups. The bulbs themselves are made of 8 separate boards with six 3528 SMD LEDs. I found a spec sheet that tells that the 3528 LEDs have a forward voltage of about 3.3V, forward current of 60mA, and dissipate 200mW. I'm not 100% sure but it seems the bulbs are wired as 8 parallel boards, with the six individual LEDs in series. I've attached a circuit diagram and I'm thinking I need to just find the right size resistor to make it work. If so, what size resistor do I need? I've done the math several times and I don't get the same answer twice. What am I doing wrong? What wattage would the resistor need to be?
As a separate question closely related, I purchased a handful of 30W high power LEDs for a different style bulb running off the same power source. The bulb to be replaced is a 250W bulb and I will need 4 of the 30W LEDs to give the same amount of light. I can't even light two of these LEDs in series and before I try wiring them in parallel I need some advice on that as well. These LEDs operate on 32-34V DC and the limited info that I can find indicates a forward current of 1000mA and that the forward voltage is the same as the input voltage. I don't know if it's a bad translation or if the forward voltage is indeed the same as the input but that seems very suspicious to me. Does anyone have any thoughts on that? If wiring in parallel is the way to go, what size resistor would I need in that case.
Appreciate the help!
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