Make a Microwave oven on a small-scale

[Dazza]

Ante, those questions are something I think I will only know, by research and experimenting .  Sometimes the most unlikely solution to a problem, can sometimes be the best solution.  Or even lead to new technology/discoveries.  

You would expect that maximum resonating effect upon the water molecule, at its ideal frequency would yield the best results.  Maybe I could even look at experimenting with electromagnetic fields, although I cannot see what affect it would have, if any.

I sure am in for a lot of trial and error, to get this system right .

[Ante]

Dazza,

Yes that

[Dazza]

I don't know about warning the Swede, but discussing with him how we can ensure his extensive range of high quality home-made alcoholic beverages, can be kept safe and sound, would be a priority .

Safety is always at the top of my list, especially when dealing with things I am unfamiliar with.

Ante, tips on safety are always welcome, no matter how trivial it may seem.

[Trigger]

May be this site, will give you some ideas in the experiment.....

http://www.geocities.com/vsurducan/electro/micro/micro.htm

[Ante]

Trigger,

I like the self-programming unit, didn

[EnigmaOne]

To the issue of making the magnetron in question smaller:
You're dealing with physically and electrically resonant structures.  If you change the proportionate size of the magnetron cavaties, you'll be--in my understanding of the matter--increasing the microwave frequency of the overall design.  It's likely that dertain driving components will have to be changed commensurately.

It looks like a full re-work, from where I'm sitting.

[Dazza]

Thanks for your reply Enigmaone ,

I was hoping, but didn't think it would be as simple as scaling down a magnetron .

Going by what you have said, I think it would be a task far greater than I could hope to achieve.

Maybe it would be a better option, to scale up my project to suit a standard microwave magnetron, for experimentation.

[Alun]

A low power microwave generator, you could build a 2.45GHz ocillator and connect it's output to a RF power amplifier.

This solution is easier said than  done, as building a stable 2.45GHz ocillator is quite tricky, you might be able to do it by using a PLL to multiply up a crystal ocillator. The only way to get power microwave amplifiers from solid state devices is to use HEMTs orGaAs MOSFETS in class E configuration.

[EnigmaOne]

Having only just dropped into this board, and only skimmed this thread, I may have missed this:
Do you really need the power out of the end device that your musings imply?

You could go with low-power microwave diodes if you only need to bounce microwaves around a bit.  (Ranging, tracking, etc.)

[Dazza]

Hi Alum,EnigmaOne,

I'm wanting to experiment with microwaves and the resonating affect upon water molecules, to try to increase the production of hydrogen in conjunction with electrolysis.

I don't need a great amount of microwave energy for experimenting.  I am new to Electronics and the simplest way for me to produce microwave energy was by using a magnetron, which I am a little reluctant to use because of the great amount of microwave energy produced that I do not need for experimenting with.

I would greatly appreciate some guidance/examples on ways of producing microwave energy.  I'm afraid the methods that use suggested, is a bit over my head I need some examples to learn/understand from .

Also it would be very useful to be able to vary the frequency for experimenting, that was another downside of using a magnetron, although I've got no idea how I can accurately measure the frequency, I don't have much in the way of test equipment .

 
The link below is basically where I started with this project.

http://www.electronics-lab.com/forum/index.php?board=28;action=display;threadid=1321

Thank you for your reply.

[Alun]

Is the microwave frequency equal to the resonant frequency of water?? When the microwave applied, the water molecule will vibrate more fiercely?? and finally generate heat??

anyone can confirm this??

No the lowest resonance of water is around 28GHz

This is a change of pace ante, and for a change I do have some answers.  How I came about to understand how microwave ovens work. It was many years ago and I was working as a labourer for a small electrical company for about three months, probably the most interesting and exciting job I have ever had, they also had a small electronic repair shop which had their first microwave oven come in for repair.  There electronic technician had left some months earlier and they had employed a young electronic enthusiast until  they could find someone qualified.  As an interesting point, he was completely illiterate and he could outperform any electronic technician they new.  Very encouraging for me ante.  So they could not let their technician repair it, too dangerous and they were already taking a big risk letting him repair other equipment. One of the electricians had taken an interest on how microwaves worked.  So it was the task of the qualified electrician and the electronic technician to fix it, and I was lucky enough to be able to offside, there was quite a lengthy discussion on how microwaves worked.  So now that I board you ante , I will try to explain what I learned from them on how microwave ovens work.

The frequency of the microwave was chosen because it could penetrate matter to a certain degree.  If the frequency was chosen to high or to low the microwaves would either pass through matter or penetrate very little, so a frequency somewhere in between that could penetrate to roughly a central point, of the type of matter that will be penetrated. which of course is different types of food water etc, now as I am to understand, it doesn't really matter the amount of power you apply to the frequency being radiated, within reason. The penetrating effect will be virtually the same.  So cause and effect, the microwaves energy have penetrated matter to appoint where they can go no further.  The molecules absorbed the energy from the microwaves causing them to vibrate, the friction of the molecules vibrating or rubbing against each other generating heat. so if you want a greater effect that is generate more heat, you apply more power to the same frequency.  The same principle would apply to radar, the frequency is chosen to be able to penetrate matter reasonably well with as little effect on the molecules as possible, which in this case is the molecules/matter in the atmosphere, and also not to be able to penetrate other types of matter such as aircraft, in this case the signal will bounce back to be detected.  So for  radar to be capable of detecting aircraft over a great distances, you would need to apply more power to the chosen microwave frequency, because of the loss of energy absorbed by the matter/molecules in the atmosphere.  Submarines also use radar and the same principle applies, although if they want to detect other submarines over a great distance, they would need an enormous amount of power due to the loss of microwave energy penetrating through the water.

Hopefully I'm not too far off the mark .

As you said 2.45GHz was chosen because it has the right level of penetration, 28GHz would be absorbed right at the surface.

I doubt submarines use radar underwater, as far as I'm aware they use sonar and not radar. Low frequency radio waves can travel great distances through salt water but microwaves get absorbed within a few meters. Low frequencies are useless for radar because the wavelength would be much longer than the boats and submarines you want to detect, VLF radio is used for communication with submarines though.

Ante, those questions are something I think I will only know, by research and experimenting .  Sometimes the most unlikely solution to a problem, can sometimes be the best solution.  Or even lead to new technology/discoveries.  

You would expect that maximum resonating effect upon the water molecule, at its ideal frequency would yield the best results.  Maybe I could even look at experimenting with electromagnetic fields, although I cannot see what affect it would have, if any.

I sure am in for a lot of trial and error, to get this system right .

Microwaves mostly heat water by causing the molecules to vibrate but they also induce electrical currents and these also cause heating. These currents might help with the electrolysis but I doubt it as they're AC and the negative cycles would cancel the positive  cycles. I can't see how microwaves do anything else but heat water, if you want to increase the efficiency of hydrogen production then why don't you just add salt to the water, you will also produce chlorine & sodium hydroxide.

Building microwave oscillators is difficult but there is lots of information available on the Internet, you want to vary the frequency so a Voltage Controlled Oscillator is probably the best solution as variable capacitors and inductors won't work at microwave frequencies.

You might be able to buy a single chip microwave VCO then you could just connect it to a pre-built power amplifier module.

Also I know it sounds silly but have you tried running a microwave of a VARIAC, you might be able to reduce the voltage and lower the power.

[Ante]

Hi Alun,

Do you really think a magnetron would work with a variac? I was thinking of the magnetron as a kind of electric

[Alun]

My understanding is that a magnetron behaves electrically like a diode. have you ever tried to construct a single diode voltage doubler?  I could be proven wrong but I have a feeling that that it would be impossible. I believe the magnetron acts as the second diode in the voltage doubler circuit in the microwave, as long as the voltage across the magnetron remains above it

[Ante]

Hi Alun,

This is interesting; I thought it needed a minimum voltage to remain resonating? Below this it would not work properly since the