ethernet frequency and power on ethernet
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Posted by praveen on October 25, 2004, 4:04 am
Please log in for more thread options I am want know the frequency of the ethernet data so that i can decide on the value of the inductor through which i can feed DC power. I have heard the ethernet can range from DC to 10 Mhz (10TBase), in this case i cannot feed power on ethernet. Yes i know about power on ethernet but the power i want to transfer is 60 W, so i feed the power directly to the line I need what is value of the inductor i have to choose. Waiting for reply Regards Praveen | ||||||||||||||||||||||||||||||||||||||||
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Posted by on October 25, 2004, 11:11 am
Please log in for more thread options I'm not sure you can, and still be legal. The ampacity of the wire is going to limit your current, the various codes for low-voltage wiring are going to limit your voltage, and the intersection of the two is going to give you your maximum power (minus line losses). 802.3af peaks out at about 20 watts input to the cable (15.4W per device), though you might be able to cheat and use all four pairs to double your power. The standards are a nightmare to parse, but it might be possible. Dunno what standards you have in India, or if this is for commercial operation or not. Can you pull another cable? | ||||||||||||||||||||||||||||||||||||||||
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Posted by glen herrmannsfeldt on October 26, 2004, 7:18 am
Please log in for more thread options William wrote:
> praveenkumar1979@rediffmail.com (praveen) wrote:
>>Yes i know about power on
>>ethernet but the power i want to transfer is 60 W > I'm not sure you can, and still be legal. The ampacity of the wire is
> going to limit your current, the various codes for low-voltage wiring > are going to limit your voltage, and the intersection of the two is > going to give you your maximum power (minus line losses). 802.3af > peaks out at about 20 watts input to the cable (15.4W per device), > though you might be able to cheat and use all four pairs to double > your power. The standards are a nightmare to parse, but it might be > possible. Dunno what standards you have in India, or if this is for > commercial operation or not. Can you pull another cable? If it is 15W per pair then he should be able to get close to 60W with four pair. (If it is limited by cable heating then it will be a little less.) I would have tried center tapped transformers before using inductors to isolate it. It is supposed to be that three phase AC makes the most efficient use of its wires, so three phase between three pairs might do it. That is, if you are limited by average current squared and peak to peak voltage. It shouldn't be much harder to keep 60Hz away from ethernet, though it could run at a higher frequency if you have to generate it anyway. -- glen | ||||||||||||||||||||||||||||||||||||||||
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Posted by on October 26, 2004, 2:46 pm
Please log in for more thread options >William wrote:
>> praveenkumar1979@rediffmail.com (praveen) wrote:
>>>Yes i know about power on
>>>ethernet but the power i want to transfer is 60 W >> though you might be able to cheat and use all four pairs to double
>> your power. >If it is 15W per pair then he should be able to get close
>to 60W with four pair. (If it is limited by cable heating >then it will be a little less.) It's actually pairs of pairs, so he could double the power. Google for the PoE spec... | ||||||||||||||||||||||||||||||||||||||||
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Posted by Walter Roberson on October 25, 2004, 11:29 am
Please log in for more thread options :I am want know the frequency of the ethernet data so that i can decide
:on the value of the inductor through which i can feed DC power. :I have heard the ethernet can range from DC to 10 Mhz (10TBase), in :this case i cannot feed power on ethernet. I don't know about DC, and I don't recall the details about 10BaseT, but at the higher bit rates, the frequency is not just 1/(megabits per second): instead, they use a slower carrier and more bits per symbol. Some error correction is used, so the raw number of data points sampled exceeds the nominal bandwidth. 10/100/1000 BaseT are all async, so when there is no data going through, there are no pulses on the line. I never looked deeply enough to find out whether it uses a DC carrier or if the line floats free. If you are using 10BaseT, then several of the wires on a typical Cat5 8-wire RJ45 setup are not used at all (not even as grounds): if you need to carry power, could you perhaps use those wires? This might not help if you are running Cat3 instead of Cat5. -- Can a statement be self-referential without knowing it? | ||||||||||||||||||||||||||||||||||||||||
>ethernet but the power i want to transfer is 60 W