I've been dreaming for a long time about ways to find out if there is a buried rebar at one of the church lot corners where it seems likely there was significant fill, and under a large power line where the Shoenstedt has so much hum it is hard to sense delicate changes. It wouldn't be good to dig a huge hole looking for it, since there is at least a foot discrepancy depending on where you measure from.?ÿ So I have an engineering study underway for a method to enhance the magnetization of such an iron.
https://www.dropbox.com/s/p68u4tlshf2r2mu/Magnetizer.doc?dl=0
It uses a capacitor bank charged to 150 to 200 volts and dumps the charge into a coil lying on the ground over a suspected site.?ÿ The equations say, surprisingly, that it doesn't matter how many turns of wire are in the coil other than to slow down the discharge pulse.?ÿ More wire makes stronger field at the same current, but the additional resistance reduces the current for a given voltage so the field doesn't change. I have saved a pile of 9V batteries changed out from smoke detectors and wireless mics and strung them together to charge the capacitors.?ÿ It's amazing how much oomph you can get out of those puny batteries when you store it up in the capacitors.
I tried it out and found a vertical 10d nail 6 inches down - surely not the 1958 monument.?ÿ I replaced it with a non-metallic rod and tried again, but found no other signal, so I put the nail back.
Now you've got me curious.
N
Hey Bill,?ÿ
Nice work.
When I worked in Geophysics for UXO, we were using a device called a metal mapper.
Similar idea, works in the time domain, impulse of current and then the receive coils detect the Eddy currents from the initial impulse to detect and define orientation and depth based upon intensity.
I like your version esp because the DIY aspect.
Keep us posted on how it goes please.
?ÿ
How much capacitance you got there?
More than I need, but I had 12 x 820 uF = 9800 uF at 200V laying around from a ham swap meet so I used them all. There are details of design tradeoffs in the Dropbox paper, if you can wade through it. I haven't actually measured the pulse length nor the speed with which the iron magnetizes, but think I probably have overkill in that respect.
I wish I'd had 4 or 5 pounds of #18 magnet wire, as that would give me a lot more peak field, but used the spool of #22 I had to see what would happen. The wire size and voltage set the field, and the number of turns on the coil the speed with which the capacitors discharge. And the surge the switch has to handle.
If anybody is considering something similar, a friend recommended these inexpensive battery-to-higher-voltage modules so you could work off 12V or such.
https://www.ebay.com/itm/294107595958?hash=item447a2dc4b6:g:rz8AAOSwzVxgbSdh
I have been playing with a simulation and learned a few tidbits about the effect of additional iron, and made a few other minor changes.?ÿ Updated file:
https://www.dropbox.com/s/p68u4tlshf2r2mu/Magnetizer.doc?dl=0
The simulation give you a view that is like a slice of the lemon to represent the behavior in the whole lemon. The tall boxes are air in this picture but could be selected as steel to see what effect they had on the pattern.
@bill93?ÿ
The whole thread is not only interesting, but also thought provoking. Kudos to you Bill. Patent it before someone else does. ?????ÿ
... and try not to electrocute yourself in the process.?ÿ A bank of big capacitors can do some real damage.
I have some big caps that I pulled out of an old solar inverter, and some more that I salvaged from an ancient industrial-size Cisco server.?ÿ And I'm wondering if the 40-ish lb toroidal transformer from the inverter (wound with 12 ga copper) might have some application to this kind of project.
... and try not to electrocute yourself in the process.?ÿ A bank of big capacitors can do some real damage.
I have some big caps that I pulled out of an old solar inverter, and some more that I salvaged from an ancient industrial-size Cisco server.?ÿ And I'm wondering if the 40-ish lb toroidal transformer from the inverter (wound with 12 ga copper) might have some application to this kind of project.
... and try not to electrocute yourself in the process.?ÿ A bank of big capacitors can do some real damage.
I have some big caps that I pulled out of an old solar inverter, and some more that I salvaged from an ancient industrial-size Cisco server.?ÿ And I'm wondering if the 40-ish lb toroidal transformer from the inverter (wound with 12 ga copper) might have some application to this kind of project.
... and try not to electrocute yourself in the process.?ÿ A bank of big capacitors can do some real damage.
I have some big caps that I pulled out of an old solar inverter, and some more that I salvaged from an ancient industrial-size Cisco server.?ÿ And I'm wondering if the 40-ish lb toroidal transformer from the inverter (wound with 12 ga copper) might have some application to this kind of project.
What's the voltage rating and capacitance??ÿ
Safety:?ÿ I try to follow the one-hand rule while charging and discharging, and everything is floating from ground. I put in a safety discharge resistor in case the capacitors want to build up voltage from buried charge, or if I need to dump them due to a broken connection.
On the plus side:
-Your wire that big could allow a nice huge current pulse.
-Those capacitors could turn out to be good for this.
On the down side:
-wire is going to be a huge amount of work to remove from a toroid.
-current may be limited by the resistance in the capacitors unless you have a lot of turns.
-12 ga. is going to dump those capacitors in a very short pulse unless you use an excessive amount of wire.?ÿ I haven't really figured out the length of pulse needed, but there was something I read (and quoted in the linked paper) about the flux taking milliseconds to "soak in" to iron unless you have enough strength to saturate it, which you probably won't have at the depth you are interested in. So you need lots of wire to slow the pulse down.
If you have any questions on the linked writeup, let me know, either in this thread, by a message through my profile, or my email also given in the profile.
I suppose that was faked for the movie.?ÿ To do that, it would have to be stronger than MRI scan magnets, and very dangerous if you have any iron alloy in or on your body. Besides ripping stuff away from you, if the field builds up too fast (MRI machines limit this) it could induce currents to overheat your rings for instance.
I once saw a demonstration of an MRI machine where they had a crescent wrench on a rope, standing out horizontally trying to get to the magnet.
Corrections to the writeup are ongoing, so if anyone is interested, please check the link above for the latest.?ÿ I just corrected a major scale error on one of the graphs.
Have you considered what effect the "large power line" you are working under may have on the coil and any voltage that might create?
I wish I'd measured it for curiosity. My intuition, based on the amount of hum on the locator's tone versus the response to changing orientation in the earth field, says it wouldn't generate more than a fraction of a volt AC in the coil, which would be negligible compared to the DC pulse. Also, when the coil lays on the ground, its axis points nearly at the power line, so that is near the orientation for least AC pickup.
In case anyone is interested in having the latest, I made some minor edits to the paper linked above.
