verolom
join:2002-03-23
Eagleville, PA
 ·Comcast
1 edit | reply to cornelius785
Re: Clue
So most dwellings have two loops, each is 24AWG or thicker. This gauge can safely carry what, maybe 500mA? So with two loops on -48V at 1A we have 48W of usable DC power. If the damn ONT consumes much more, then Al Gore will have much bigger issues with it than replacing lead-acid batteries every 5 years by Joe and Jane Doe. 
We are talking DC power, already provided on these loops to power offhook phones. For the ONT, power supply filters can be put in place (capacitors) so that the ONTs do not interfere with DSL or POTS lines in the same cable. |
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bogey780
join:2004-03-19
Here
| 'most dwellings have two loops, each is 24AWG or thicker'
Correction: most dwellings may have two loops, each maybe is 24AWG or thicker.
DC doesn't work that way. It doesn't run like AC which is why Westinghouse won and Edison lost when it came to standardization. You can't transmit DC long distances effectively unless you have high gauge wiring and enough of a step-up to reduce voltage drop. |
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bogey780
join:2004-03-19
Here | reply to verolom
And I think you mean diode and not capacitor. |
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shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA
 ·Atlantic Nexus
| reply to bogey780
DC transmits better than AC. There are now several DC high-V power lines. They use DC because you don't get the reactive loss of the lines.
The problem with DC on mains power is you can not step it up or down. Edison had to run everything on one voltage because he could not step it up or down. Westinghouse (Tesla) could step up the voltage for lower losses, then step down locally.
As far as the local loop, I have worked with devices powered over 24GA wire. For a device that used about 8W, at 24 volts, the best we could do was about 700' on a single pair and 1000' on 2 pair.
--
Scott Henion
Embedded Systems Consultant, shenion on #ATU @irc.freenode.net
SHDesigns home |
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patcat88
join:2002-04-05
Jamaica, NY
| reply to verolom
here is the math, lets assume 90v, since thats what a telephone rings at.
90 volts
0.0842 ohms per meter for 24 gauge
60000 feet, FIOS uses BPON, 12 mile limit from central office
90*(90/((60000/3)*0.0842))=4.8 watts
20000feet
90*(90/((20000/3)*0.0842))=14.4 watts
heck, I dont know how RF noise friendly this is, but if we use 2 wires, we can use earth return, and get 2 times what is there, add a 2nd pair, same thing
»fios ont power req
18watts with TV+internet+phone running (not on emergency power), emergency power will be less
so yes its feasible, you'll probably need a new ONT tho, I dont think the current ONTs are as optimized as they could be when running on emergency power, so I dont think it would be as simple as plug battery pigtail of BBU into adapter and 2 screw terminals on the other end of adapter. |
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verolom
join:2002-03-23
Eagleville, PA | Thank you. Probably the ONTs run on 12V or 6V (additionally downconverted to 5V) so some power conversion and loss will occur. |
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bogey780
join:2004-03-19
Here
| reply to shdesigns
Thanks for the info on HVDC.
The way I took it the loss and inability to step effectively is what killed DC because placing power plants locally killed the idea for most Americans. While AC could be transmitted at high voltage and stepped down to low voltage locally.
Either way, that's why I liked BellSouth's FTTC engineering. It used 22ga cabling to power 130VDC systems. I could see an eventual move to FTTH from there could possibly allow for telco provided power to the house (which was within 1kft always). |
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