Harvesting Antenna circuit - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: May 07, 2017, 07:28:17 am
content: A Copper antennaB harvesting legs, with 0.10uf to 0.22uf CapacitorsC Swtiching Regulator, possibly use:http://www.linear.com/product/LTC3105Battery is 1.5v LR44.Any problems with my circuit?How many harvesting legs do you think I'll need?The ground won't be connected all the time (carrying it around with me). Which shouldn't be an issue, provided I ground - then charge battery from capacitors; all capacitors return to zero charge. Correct?Probably need to make antenna & wires from Silver, and make antenna very large and flat.Might need to have quite a few of these antenna circuits to actually be worthwhile.

author: mc172
author_rank: Frequent Contributor
timestamp: May 07, 2017, 09:18:42 am
content: If you're not within a few hundreds of metres of a very high power transmitter, don't waste your time.

author: Ian.M
author_rank: Super Contributor
timestamp: May 07, 2017, 09:26:49 am
content: Even if you are, the proposed circuit is junk. The diode will charge the capacitor until the developed voltage is enough to keep it reverse biassed then nothing further happens. There is no way of getting the charge out of the capacitor and into the Dc-DC converter.You need two diodes and a capacitor configured as a charge pump and either a loop antenna or an antenna with an effective counterpoise so you have a local RF AC voltage difference you can rectify. The only reason to have multiple harvesting circuits connected to the same antenna is if they are tuned to different frequency bands, however the antenna will be inefficient on bands that are far away from the one it was designed for.

author: BrianHG
author_rank: Super Contributor
timestamp: May 07, 2017, 10:02:23 am
content: Out of curiosity, I used to live 1 block from high voltage lines. My workbench's outer frame was metal and would give me quite a shock when I touched it since I was in the basement of my house and exposed to the concrete ground as the basement was unfinished. I used to be able to light a few LED just by touch.I was wondering what would happen if I extended an tuned this antenna, connected to a step-down transformer as the voltage was really high, but, low current. Could I have created any usable power above the few mw I was already getting?Damn HV power lines always interfered with my scope and audio/video equipment.

author: Ian.M
author_rank: Super Contributor
timestamp: May 07, 2017, 10:19:48 am
content: 1 block from HV lines in a concrete basement wouldn't have that much field. Something else was going on - perhaps a ground fault.

author: BrianHG
author_rank: Super Contributor
timestamp: May 07, 2017, 10:46:31 am
content: 120Kv lines feeding all of downtown Montreal. My bench table steel outer frame was 32 feet long metal L beams welded together into a 2 rectangles, supporting 2 wooden table top (8x16feet), perpendicular to the power line, with 8 vertical spiked legs, no connections to anything other than that the entire outer L-beam structure was all welded into 1 huge solid piece. Note that the height of the table-top's steel frame was approximately ground level. My basement didn't go too deep underground.During the muggy hot days and freezing cold mornings, you could hear a hum coming from the frame beams as the city drew much more AC power, as is the case for many houses metal ducting along the blocks of the power lines. Now that I moved out, the city residents are petitioning to force the power company to bury and insulate the power lines as they effect all the houses in the area. Even when there was a total blackout in my city of Dollard, there was still the hum on the table if the City of Montreal was still getting power.Note that if I look out at the window in my basement from the height at the top of my table, the power lines are high enough that they would be in direct line of sight, (no power going through concrete or earth) except for the trees and my neighbours house which are in the way in my backyard.I attached the location of my old house. I cant seem to find a photo of my workbench.

author: Ian.M
author_rank: Super Contributor
timestamp: May 07, 2017, 11:11:40 am
content: Definitely something else going on. The field round a single current carrying conductor drops off proportionally to 1/r2. For a balanced three phase line their fields approximately cancel at r>>w (where w is the separation between conductors) leaving a residual 1/r3field. You had the short end of the bench 'coil' parallel to the line, which meant the long sides provided negligible coupling so all there was was the differential between the field at r and the field at r+16' (as the middle shorted across the 'coil') over the 8' length of the ends. Also how would induced current in a shorted turn develop enough EMF to ground to be detectable to touch?If there was enough E field from the power line to cause problems in your basement, getting or out of a vehicle on Boulevard de Salaberry would have been risking a lethal electric shock, and if it was from the H field it would have been killing vehicles by burning out their engine management computer.

author: BrianHG
author_rank: Super Contributor
timestamp: May 07, 2017, 11:22:20 am
content: I have no other explanation. There were no cell towers or transmitters near by. With such a large metal structure, I think maybe it might have been tuned to an AM radio station and I was getting a RF burn, enough to light 2 green LEDs when holding 1 leg to the table the other in my hand (2 LEDs in parallel with opposite polarities), but that also seems inplausible. The booster station seems a little too far away to have any effect. What else can magically create electricity like that? Neither I or the table wasn't wired to anything.Correction, the previous lines are 120kv, and they are over powered since the power company wants to upgrade them to 315kv.

author: Ian.M
author_rank: Super Contributor
timestamp: May 07, 2017, 11:55:08 am
content: If you ran a multi-turn coil around the perimeter of a large property (say 100 yards frontage directly onto the power company easement and several hundered yards plot length away from the easement), with the section of the coil along the frontage on poles to get it up level with the line, and the far side of the coil buried you'd probably get enough to run some energy efficient light bulbs.The most likely cause was a neutral fault causing a big ground potential difference across your property.

author: cdev
author_rank: Super Contributor
timestamp: May 07, 2017, 12:12:11 pm
content: If you properly coupled that energy into a joule thief circuit, you definitely could. There is a lab at Georgia Tech that publishes tons of research on how to do it.I forget the professor's name, but his home page is a wealth of info on various means of powering microelectronics from ambient energy using all sorts of methods. A one stop shop for info on the technologies you could implement it with. Will add the link later when on desktop with better keyboard.Look for planar printed antennas. That's how I found it.

author: cdev
author_rank: Super Contributor
timestamp: May 07, 2017, 12:43:53 pm
content: I like to hike along a trail near where I live where there are high voltage lines and I get a shock from my camera tripod, which is carbon fiber.ThaIn a large urban area there is often enough RF to rectify and measure. It's definitely above the half a volt needed for a silicon junction.Back in the 80's for a few years I lived just a stone's throw from Sutro Tower in SF. A big TV and microwave antenna that towers over the city.There the problems were definitely caused by RF.People who lived a bit higher up would have fluorescent lights in their houses often glow when not turned on, when it was foggy.The fog greatly magnified the RF issues.

author: SeanB
author_rank: Super Contributor
timestamp: May 07, 2017, 02:33:51 pm
content: With your frame consteucted of a low resistance loop of a good conductor, and with a high permeability core in the iron itself, you would have a large circulating current in it. Best would have been to cut the loop at come point, just by cutting a beam, and placing an insulating spacer, and see the low AC voltage developed across the open ends, and measure the AC current in the loop. A simple current transformer ( single turn primary, 100 turn secondary, would probably develop enough power to light a few bulbs, or put a toroidal transformer centre around the beam, and see what the assorted windings develop.

author: Ian.M
author_rank: Super Contributor
timestamp: May 07, 2017, 02:43:54 pm
content: Quote from: SeanB on May 07, 2017, 02:33:51 pmReally?At five times further from the HV line than the boulevard, you'd only get 1/125 of the current that it would have given at that point. If the circulating current in the bench frame was 1A, the frame of a truck on the boulevard would have been carrying over 100A, enough to blow out the wiring loom if there were multiple ground connections.

author: Audioguru
author_rank: Super Contributor
timestamp: May 07, 2017, 04:07:41 pm
content: An LR44 button battery cell is an alkaline cell thatis not rechargeable!.

author: SeanB
author_rank: Super Contributor
timestamp: May 07, 2017, 04:10:38 pm
content: Truck chassis is a lot of small loops, as there are a lot of shorting bars in a Ladder chassis, and all the wiring will be well shielded simply by virtue of them being enclosed inside the c sections to protect from damage in use from just driving. long bench with single large loop would however pick up a lot more open field from the kA current flowing in the power line. Depending on the line construction, it could be carrying a current at peak load of between 1kA to over 10kA, really depending on the number of cores on the poles, and the particular style of line geometry, and especially in a transition zone between pole types there can be high magnetic fields.

author: BrianHG
author_rank: Super Contributor
timestamp: May 07, 2017, 05:02:36 pm
content: This is as good as google maps can generate a photo of the power lines & boost station next to my house. I see 6 conductors on the HV lines.I've attached the actual size and shape of my 3 piece workbench table beams. Yes, the structure runs the length of the house, it is that long across the 3 tables. My actual house is 1 city block further away from the transformer station. I'm sure it's some sort of fluke that the huge table length with 3 rectangular holes, wood tabletop panels in the middle, somehow tuned into 60hz and happened to be the right distance to tune into a wave crest, well enough to shock, but you must admit it is long enough with thick enough metal in an awkward shape to capture more power than just a small rod antenna copper wire, or a lump of metal like a car or truck.

author: SeanB
author_rank: Super Contributor
timestamp: May 07, 2017, 05:26:46 pm
content: 6 conductors simply is a standard redundant 3 phase delta supply line, with somewhere an earthing transformer to balance it. As you have a half turn loop around your house, very likely it would induce current into it, would have been interesting to have used a clamp ammeter and seen the circulating current in the steelwork of the table.Power line current ratings depend on the number of cable bundles that make up each individual line, not on there being 6, that just makes it double the standard 1kA rating. your power company could have rated it higher or lower, depending on the maximum span length they have on the segment, and the amount of droop they allow on the hottest day of the year at peak draw in the late afternoon. you could be anything from 600A to 1500A maximum on the same conductor set, depending only on the droop allowed and the length of the line, and the allowed droop due to I2R losses.

author: BrianHG
author_rank: Super Contributor
timestamp: May 07, 2017, 05:35:56 pm
content: I just realized this, drawn from above, my 3 table top steelwork frame looks exactly like a slice of a 3 phase E core transformer.

author: Cliff Matthews
author_rank: Unknown
timestamp: May 07, 2017, 05:53:30 pm
content: Never experienced anything odd living almost right under the wires of the 220KV Gatineau hydro corridor.https://www.google.ca/maps/place/43%C2%B043'44.7%22N+79%C2%B017'58.7%22W/@43.7291183,-79.2998584,68m/data=!3m1!1e3!4m5!3m4!1s0x0:0x0!8m2!3d43.729086!4d-79.299645?hl=enCould be something from your sub-station upsetting grounding?

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 07, 2017, 07:21:26 pm
content: Wonder how effective it would be to build an antenna that is tuned to 60hz. It would need to be 3,125km long.