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Registered Member #4274
Joined: Mon Dec 19 2011, 03:10AM
Location:
Posts: 47
So I have 2 magnetrons from a microwave and I would really like to do something with them other than take the magnets out. I remember hearing about microwaves being used to transfer energy over long distances, so something like that. I would want to know how I would collect a reasonable amount of this energy, and safely so I don't burn my insides. What materials absorb microwave radiation, what materials reflect? I would ultimately like to make this a demonstration video on wireless power transfer means (not a live demonstration) and really get to experiment with it myself. It would be nice to set the magnetron up on one end of our shop, the coil on the other end, set up a video camera to record, turn on the magnetron (from outside the shop), and see how it works. How long will microwaves bounce around until they stop, and what things could happen to nearby electronics/ possessions such as the camera, powertools, chickens behind the shop, etc. Thanks!
Registered Member #4118
Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140
If you want to transfer energy via microwaves you're going to have to focus them. Metal reflects them, anything that heats up when you microwave it absorbs them, and stuff like glass and some plastics let microwaves pass through them. I don't know how you would collect the energy though. Since they're really just radio waves you might be able to use a radio receiver tuned to 2.45GHz, but I don't know how well that would work. Unless your skin starts getting hot you don't have to worry about any bodily harm. I once read that magnetrons make nice hand warmers... You do need to keep electronics away from it, though. They'll just get fried if they get exposed to the beam.
Registered Member #2025
Joined: Fri Mar 13 2009, 05:39PM
Location:
Posts: 16
Why about just having the magnetron heat up water, running a small steam generator or something of the sort? Yes, I know, not really electronic, heh, but still an idea!
And yeah, seems the major identifier of risk is when your skin starts heating up, got that from wiki. "Less-than-lethal weaponry exists that uses millimeter waves to heat a thin layer of human skin to an intolerable temperature so as to make the targeted person move away. A two-second burst of the 95 GHz focused beam heats the skin to a temperature of 130 °F (54 °C) at a depth of 1/64th of an inch (0.4 mm). The United States Air Force and Marines are currently using this type of active denial system."
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
hak8or wrote ...
Why about just having the magnetron heat up water, running a small steam generator or something of the sort? Yes, I know, not really electronic, heh, but still an idea!
And yeah, seems the major identifier of risk is when your skin starts heating up, got that from wiki. "Less-than-lethal weaponry exists that uses millimeter waves to heat a thin layer of human skin to an intolerable temperature so as to make the targeted person move away. A two-second burst of the 95 GHz focused beam heats the skin to a temperature of 130 °F (54 °C) at a depth of 1/64th of an inch (0.4 mm). The United States Air Force and Marines are currently using this type of active denial system."
Some link that might interest you:
I remember seeing this being demonstrated on TV, a nasty device marketed as a crowd control beam or something like that. It is quite sickening really.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
wrote ... I would want to know how I would collect a reasonable amount of this energy, and safely so I don't burn my insides. What materials absorb microwave radiation, what materials reflect?
ALL materials reflect, which is why you need to be really careful (and knowledgeable) with high power radio sources because it can bounce around in interesting ways. When you have ~1,000W transmitting from a high gain antenna (or even a low gain antenna) it doesn't take much of a reflection to get dangerous because the starting power is so high. The reflection dies out when enough has been absorbed in each reflection or it has spread out wide enough from multiple reflections that the power density is no longer a danger. The best reflectors are conductors, the better the conductor the better the reflector, but all materials reflect because they have different dielectric constants from air or each other. I'm not sure what a good way to absorb the power is. Water is a good absorber (it reflects a decent amount too), though I'm not sure how you could shield yourself with water. Carbon impregnated foam or lossy magnetic materials are the usual absorber materials at antenna test ranges, but neither are cheap. Pretty much all material absorbs to a certain extent so the more stuff between you and the magnetron the better. Maybe you can isolate your whole test range in a faraday cage if you keep it small enough.
Rectennas (fancy word for an antenna with a suitable high speed rectifier diode) are the usual way of converting RF power back into DC power, and they can be pretty efficient if you're transmitting a constant frequency signal, as with a magnetron, so you can do harmonic input matching networks. Generally a rectenna array is used because each element can't handle a whole lot of power. But turning it into heat power as hak8or suggests is easy and could still be an interesting demo and experiment. You could do some calorimetry!
wrote ... Unless your skin starts getting hot you don't have to worry about any bodily harm. I once read that magnetrons make nice hand warmers... You do need to keep electronics away from it, though. They'll just get fried if they get exposed to the beam.
This is pretty dangerous, don't try this at home (or anywhere else).
Registered Member #4052
Joined: Thu Aug 11 2011, 04:43AM
Location: IN ,USA
Posts: 69
Most of the usses for magnetrons that I have seen are rather dangerous and almost always result in a broken camera. If ran on low power it might be able to used in a safe way. Perhaps you could modulate the input and make a AM transmitter?
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
If you take them apart carefully, and use them without the magnets, they just might give you a brute rectifier that wont generate RF, but might be neat for 2000 Volt project.
Ham radio operators use the magnets to make bases for aerials that they can stick on the roof of their car for field work.
Inside the plug base of the magnetron there is a filter system that will block RF and is good for about 10 amps.
Be sure to know exactly what metals are inside the vacuum part before you break it.
Registered Member #2909
Joined: Wed Jun 09 2010, 12:31AM
Location: fort belvoir, Va USA ( south of DC)
Posts: 145
make a faraday cage around what you are working on, like out of mirowave doors screens and such just do some research and find out what size hole will block Microwaves.
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Magnetron Uses Outside a Microwave?
