Before anyone goes out there and barbecues themselves with a USRP, two things:
1) Use Ettus Research products for power-line or hazardous voltage applications at your own risk and after careful evaluation by competent engineer. 2) VAC, Gredmann, Hitachi, Magnetica, and other companies make power-line-communications-specific transformers with IEC-approved isolation. Search for "PLC transformer". Please don't do anything with HV/line voltage without real isolation; using resistors for power line isolation is asking for trouble. --n On Tue, Feb 21, 2012 at 1:13 PM, John Ackermann N8UR <j...@febo.com> wrote: > Well, I'd put it that large resistors result in high impedance. You still > have the full line voltage across the output of the two resistors, but any > load resistance will form a voltage divider and drop the voltage very > quickly. > > A simple next step would be adding an appropriate load resistor and using > an op-amp as a follower to provide a low impedance output to drive the > BasicRX. > > I'm not sure why you'd need to unground anything -- the output is an AC > signal, and the resistors limit any current to a miniscule and safe level. > Folks have been plugging this design into all sorts of grounded gear with > no issues at all. > > John > ---- > > On 2/21/2012 3:57 PM, Evan Merewether wrote: > >> Two issues: >> 1) Large resistors results in large attenuation. This circuit attenuates >> 120VAC to ~5V for the microcontroller. >> 2) You would need to un-ground all of the components (USRP + PC + you) and >> float everything to somewhere around 60V >> >> -----Original Message----- >> From: >> discuss-gnuradio-bounces+evan=**syndetix....@gnu.org<syndetix....@gnu.org> >> [mailto:discuss-gnuradio-**bounces+evan <discuss-gnuradio-bounces%2Bevan> >> =syndetix.com@gnu.**org <syndetix....@gnu.org>] On Behalf Of >> John Ackermann N8UR >> Sent: Tuesday, February 21, 2012 1:45 PM >> To: George Nychis >> Cc: discuss-gnuradio >> Subject: Re: [Discuss-gnuradio] discussion on USRP-->Wall Socket for Power >> Line Comms >> >> On 2/21/2012 3:00 PM, George Nychis wrote: >> >>> Okay! So apparently there is some interest in power line communication >>> for GSoC. But, what we would want to do is already have a safe way of >>> connecting the USRP in to the wall socket for the student(s), and for >>> the future of GNU Radio and USRP power line communications development. >>> >>> So, as a goal of this thread I'd like to get some feedback on how we can >>> make this possible. Ideally, something off-the-shelf would be great, >>> providing the highest amount of safety for those experimenting with it. >>> >> >> Here's a very simple approach: >> >> http://leapsecond.com/pages/**ac-detect/<http://leapsecond.com/pages/ac-detect/> >> >> There was a bunch of discussion about this on the time-nuts mailing >> list, and some folks suggested changes for increased safety (including >> putting two resistors in series so that if one fails short -- which is a >> very unusual occurrence -- there's an extra layer of protection. But in >> general, with large value resistors the current is limited to a very >> safe level -- and it's current that kills, not voltage. >> >> John >> >> >> ______________________________**_________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/**listinfo/discuss-gnuradio<https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> >> >> > > ______________________________**_________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/**listinfo/discuss-gnuradio<https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> >
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