Microwave Magnetron Projects

I recently inherited a microwave oven with a damaged door latch. The magnetron works, but the rest of the oven isn't worth saving. Before I cannibalize it for parts (like the HV supply and some kewl magnets), are there any (safe and legal) uses for the working magnetron?

I'm ruling out microwave weapons, anti police radar devices, etc for obvious reasons, but if there's something to be done with this before destroying it, I might add it to my projects list.

Links to project web sites would probably be best. Thanks.

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Paul Hovnanian	paul@hovnanian.com
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Ionize some gas maybe?

John

Reply to
John Larkin

"Paul Hovnanian P.E." hath wroth:

No. At that power level, literally anything you do external to the oven box will belch dangerous levels of radiation.

The closest approximation of a safe application is a 2.4GHz ATV xmitter:

Note that the typical microwave power supply will not work for CW or TV applications without considerable modifications. 100 watts CW at

2.4GHz is still a rather dangerous power level.

Remember, you have but one life to give to your profession.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

See "RF Design" back sometime in 1989, I know I have a copy somewhere. They modded one into an ATV Tx.

I'd be interested in something new and novel. I've gutted many over the years, and usually strip them for the useful parts (microswitches, control PCBs, HV diodes and caps, thermal switches, etc.) And the magnets are very useful around the workshop. I've even made a "magnetic broom" with 6 of them mounted on an old broom handle, great for picking up errant nails, etc.

Barry

Reply to
Barry Lennox

It would be nice to direct it into a large cylindrical cavity into which a plastic bucket slides tightly. The bucket contains a solution you want to heat, which for some reason must be done in this container (e.g., solution reacts with metal or glass containers, or you don't have such, etc.).

The cavity would thus be open ended, but the water should be an effective screen, as long as it's deep enough in the bucket.

Safety would of course be an issue, but interlock switches could be provided for sensing that the bucket is firmly seated and perhaps a dielectric sensor used to ensure the water level is always high enough.

And of course, the magnetron contains four potentially valuable things: magnets, aluminum heatsink fins (a few cents), a solid copper body (maybe a buck at today's copper prices) and a thermionic heater-cathode.

The middle two are nice to me, since I melt metals, and the last would be nice to someone with a bell jar.

Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams

You might need some test equipment, say

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Martin

Reply to
Martin Griffith

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I'll toss out one extra personal experience, too. In the last year of high school, we had a science teacher with a masters in physics from Northwestern University and a grand total of 7 students in the advanced class. We used a klystron, not a magnetron, and the wavelength you are talking about is about 5 inches I think, which is somewhat shorter than what we were working with then. But we "beamed" the klystron into the classroom from a desk on one side at a "crystal" we'd built with tin-foil-wrapped Styrofoam balls stuck together with sticks. These allowed us to use watt-meters, held by hand, to measure different points on the other side of the "crystal", graph them, and derive the diffraction patterns from the resulting measurements.

I remember some tinkering to get it running well and at the time I didn't have any idea what a waveguide was, but it gave a great hands-on, macro-scale understanding to how x-ray crystallography works.

I'm not so sure I'd do anything like this with a 2.4GHz magnetron and some adapted waveguide, blasting an open room in which I was wandering around taking measurements. Also, your own body in this case may be a problem, since you are mostly water and you could interfere way too much with what you were trying to measure. So I don't think this lesson would be safe or as useful an educational tool, unless you found another way to take those measurements.

This comes from someone (me) who made "rocket candy fuel" from melting potassium nitrate and sugar in a florence flask/beaker double-boiler using boiling sulfuric acid as the bath to keep hot spots from forming (melt temp was about 300C, flash point about 400C), and where I'm nestled behind piles of sand bags I'd set up in the garage, just in case. And that was only one of many different mixtures I experimented with, including making mercury fulminate and nitroglycerin. So you might consider a little, before you beam yourself or some hapless volunteer with a dispersed 1kW beam of 2.4GHz at a distance of a few dozen feet away.

No way would I do today what I was doing back then. (Or maybe I really would, given half an excuse, and just won't say so in public. ;)

Best of luck, Jon

Reply to
Jonathan Kirwan

I'm not planning on running this thing outside of an adequate waveguide/enclosure. So nobody has to worry about my survivors going after the individual who provided me with the plans for a microwave hairdryer. ;-)

One other thing: Its my understanding that the power supply for these things is basically a constant current supply. The current is what determines the magnetron's output power. If I decide its worthwhile to modify the supply, I'm wondering how far the output of one of these can be throttled down. I suppose the datasheet might provide this info. once I get the oven disassembled.

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Cheers, James Arthur

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James Arthur

maybe using a magnetron (since the cavity is resonant to wifi band) and its small antenna inside complete to use it like a "driver" for some "can wifi antenna" connected to some WLAN stuff ?

I was thinking about that, but could not find at that time at junk yard some broken microwave oven ...

-- Regards , SPAJKY ® mail addr. @ my site @

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Spajky

Paul Hovnanian P.E. snipped-for-privacy@seanet.com posted to sci.electronics.design:

How about using it as the core of a humidifier?

Reply to
JosephKK

It works pretty well to ionise Helium for a microwave induced plasma as an ion source for ICP-MS, that is provided that you don't mind the risk of catarracts, blindness and frying your kidneys. I once walked into a lab where a senior researcher (who should know better) was adjusting one with all interlocks off and the plasma fully exposed. Surprisingly pleasing pale reddish coloured flame but I was out of there instantly. About 1kW output and a spark to start the thing at atmospheric pressure. eg.

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By comparison the RF ICPMS argon plasma flames are unpleasantly bright and UV rich but nothing like as dangerous.

Anyone without the requisite knowledge to keep the microwaves safely confined can expect to get some very nasty complications from microwave exposure.

Regards, Martin Brown

Reply to
Martin Brown

There are methods for doing so. The Next Big Thing in lighting is microwave powered gas discharge lighting. No electrodes to wear out.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Paul Hovnanian P.E.

"Paul Hovnanian P.E." hath wroth:

I hope not. None of them have come close to meeting FCC Part 15 unintentional radiator limits. The original microwave sulfur lamp was originally promoted by Fusion Lighting in the mid 1990's. The FCC sorta, kinda, maybe, somewhat killed the idea in 2003. Achrived web site at:

"Sulfur Lamps"

"FCC Rejects Satellite Radio's Petition to Ban RF Lights in 2.45 GHz Band"

"Fusion calls "timeout" in sulfur lamp race"

Unfortunately, raising the dead is a common preoccupation in electronics. LG and Island Systems Lighting(UK) have resurrected the idea. Hopefully, it experience a quick product death.

Of course, there are less obnoxious forms of plasma lighting:

Powered by a USB port. I want one.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Jeff Liebermann

Build a sulfur lamp?

Reply to
Chris Jones

Says the sulfur bulb has a design life expectancy of 60,000 hours, and that the magnetron needed to supply the microwaves has a design life expectancy of 15,000-20,000 hours. Meanwhile, I remember from elsewhere even shorter life expectancy being usual for magnetrons - I generally got the impression of 10,000 hours.

I think that would support a contention that FCC did not kill the sulfur lamp.

The Wiki article even notes that FCC in 2003 terminated a proceeding started in 1998 that otherwise would have increased regulation of RF emissions from sulfur lamp systems.

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

Actually I would suggest that "raising the dead" by those who are well aware of the initial causes of death is a very good idea: As technology advices, many old ideas that were once impractical become quite viable.

I would agree that (too) many people "raising the dead" aren't even aware that their "new" idea is quite old nor what the appropriate history is -- this seems to be the case with some fo the folks promoting wireless re-charging stations these days.

Reply to
Joel Kolstad

You remind me of my class D tube amp project.

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I do wonder if anyone's ever done it before, you know, in history...

Tim

-- Deep Fryer: A very philosophical monk. Website @

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aware

advices,

that

re-charging

Reply to
Tim Williams

"Joel Kolstad" hath wroth:

Sigh. I was afraid someone was going to take me seriously. Once upon a time, I designed a radio direction finder, where the basic principles were extracted from a 1920's radio physics book. I've done other modernization projects, from electric car controllers borrowing technology from about 1910[1], to borrowing overprice military technology, that magically became affordable.

What engineering I've done in the past, is almost all "raising the dead" if I include cleaning up someone else's mess, or picking up projects after the funding died. For a while, my title was "Post Mortem Engineering" in honor of my actual job function. Unfortunately, my constant complaining was heard by management and whatever gods are in charge of engineering, and subsequent projects turning into cloning. Instead of raising the dead, I was now re-raising the living. Sigh.

There's another benefit to raising the dead and reading up on old technology. Many of the basic principles behind today's complicated technologies are more apparent in the original crude forms, than they are in the modern implementations.

Yep, but it won't help. Most new engineers want to do everything themselves. Not invented here syndrome is epidemic. I did that for a while, until I realized that reinventing the wheel was not a very productive use of my time. So, I switched to the dark side and went to "progress through plagiarism". The result was a large collection of "Ideas for Design", competitors manuals, patents, old technical books (which I still collect), and the usual reverse engineering. My designs and career moved along much better after that, although there was one problem. I never again had an original idea.

[1] Electric milk delivery vehicles were very popular between about 1910-1924(?) because they didn't make any noise during their early morning delivery rounds.
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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

That's not "raising the dead", that's "reinventing the wheel". ;-)

Cheers! Rich

Reply to
Rich Grise

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