Rectifying signals on home AC ground and pipes... - Page 1
Forum section: electronics / projects

author: energy_hunter
author_rank: Contributor
timestamp: March 31, 2016, 12:57:59 pm
content: I run a small microelectronics business in upstate New York and I'm selling an RF-DC converter (RFD102A) and an AC-DC converter (RFD103A) for use with wireless energy harvesting or as a zero-bias detector for $12. For a demo, a fellow forum member (hendorog) suggested that I try to use my home AC ground as an antenna and see what I can pick up. I live pretty far from any base stations or radio station antennas but still I'm able to get the following from the ground pin of my AC.0.84V - signal to GND on the AC outlet and GND of the module to the plumbing0.51V - signal to GND on the AC outlet, only an open 2ft banana wire to GND of the module0.03V - 2ft banana wires left dangling0.01V - banana wires removed but still have 2ft banana wires going to the multimeter.I don't think this is practical as a source of power in my home but it could work for a very low power application circuit that only needs to work maybe once a day. When I connected a 10kOhm resistor to the DC output I only measured 0.01V vs. the 0.84V with a high impedance of the multimeter.I am wondering if anyone who lives near high-power transmission lines or a radio antenna has tried to harvest energy from these sources. Please share your experience. Gracias!

author: madires
author_rank: Super Contributor
timestamp: March 31, 2016, 01:27:52 pm
content: The mains ground/earth/PE is commonly connected to a earth rod or another proper earthing method (see your local sparky code). Metal plumbing might be also connected to the same earth rod. That's not usable as an antenna.

author: energy_hunter
author_rank: Contributor
timestamp: March 31, 2016, 02:06:12 pm
content: In the case of higher frequencies, if the electrical length to get to earth ground is a quarter of a wavelength then the electrical short looks like an open at the test point and the line can behave like an antenna or a transmission line. A quarter wavelength at 100MHz (FM radio) would give a distance of 0.75m. So since most wiring inside a house is electrically large for radio waves you would get some good reception and bad reception as you sweep frequency. My test showed that there are signals that can be rectified that are on the ground wiring of a house. Some could be due to noisey switching power supplies and other signals could be due to AM/FM radio or other wireless sources.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 31, 2016, 02:18:56 pm
content: What bandwidth is your meter? (Do you know? Can you check?)Mind that protective ground is intended to carry fault currents, so expect it to be perhaps a fraction of a volt under normal circumstances, surging to hundreds or thousands of volts under fault or transient (lightning) conditions!Tim

author: madires
author_rank: Super Contributor
timestamp: March 31, 2016, 02:31:27 pm
content: If you put an inductor between the earth rod and the mains ground you could use the ground wiring as "random wire antenna", but nothing more. BTW, the ground wiring wouldn't be a simple dipole. And anytime you plug something into a mains socket or unplug it, you'll change it. The sources of the signals you've recitified could be anything, even the current through the Y filter caps.