Russian DYI death rays

[wraper]

That is Luhansk, Ukraine. You can even hear shelling. Yes they are filming when war is going on.

No .... no, it is the Russian army in Jurmala 

Well, you know, if watch our bullshit news every day (broadcast directly from Washington) it wouldn't be hard to believe  . I know some people in Mariupol and Izmail (Ukraine), though. And they are no excited (to put it mildly) by the new government at all. I was in Ukraine myself repairing stuff when people were burned alive in Odessa (200km from where I was) by local Nazis, that day I decided to return back next day FFS.

[eurofox]

Of course the true is RT, that is the only true, no russians in Crimea to annex it 

[wraper]

Propaganda everywhere, there are no good guys. Thou most Crimean were not against it, just because they are mostly Russians. People in Ukraine west and south/east are very different, both by language and political view.

[zapta]

But he is not Russian, his name is Kyle Myers.

Here is the proof he is Russian:

[eneuro]

Ovens use half-wave rectified AC, so the magnetron runs in pulse mode.

I've made microwave oven teardown some time ago and just want to understand how those parts are connected and how magnetron is powered, while there is no specs on it about its operating voltage and power ratings 

But magnetron radiating RF element is close to 30mm (3cm long) 
I found there  http://en.wikipedia.org/wiki/Dielectric_heating that

"Consumer ovens usually use 2.45 gigahertz (GHz)—a wavelength of 12.2 centimetres (4.80 in)—while large industrial/commercial ovens often use 915 megahertz (MHz)—32.8 centimetres (12.9 in)."

and here http://en.wikipedia.org/wiki/Cavity_magnetron its principles, but there were no typical magnetrons specs.
This has two connectors only and it looks like diode connected to ground from one of this high voltage capacitor rectifiers AC voltage? 

However, those  a few turns coil in the middle of this  transformer is a mistery for the moment too, while expected high voltage windings to be connected to magnetron somehow.

I was even more supprised that this HVR-1X3 High Voltage Power Diodes Standard and Ultra Fast Recovery diode rated to 12kV 0.5A and surge current 8ms up to 30A is connected to... ground and as i remember one of HV tarsformer windings was connected to transformer case? 

How those microvawe ovens are safe-it is better not to open those things while when you see so many "DANGER HIGH VOLTAGE" tags inside starting think to do not connect it to 230VAC mains no more 

BTW: It is quite good for Dave videoblog maybe, while its circuit looks simple, but... I'd like to have its schematics and ensure it is save to touch its case 

[zapta]

This could be a great idea for eevblog teardown episode.

[eurofox]

Propaganda everywhere, there are no good guys. Thou most Crimean were not against it, just because they are mostly Russians. People in Ukraine west and south/east are very different, both by language and political view.

I know them much better than you, my wife who past away was from Lugansk, I'm married again  with someone from the south of Ukraine both native Russian speaker, don' try to teach how they are and how they think.

I was in Russia from north to south and from east to west, know a lot of people from professional and private experience.
I know very well the history including your country that I know very well including the relation with the native Latvian and the Russian minority.

I don't say that USA is always right with international politics just like Russia but there is one big difference, one is a democracy and the other a dictature with the dictator telling what 145 million people will do and they are all scare to disagree with him.

I'm a real European in soul and I'm happy that the EU and NATO exist because we never got such a long time peace in Europe.

This board is not the right place for this kind of discussion but Ukraine should have the right to decide what they want, stop corruption and start democracy without any action from Russia.

We are not in the middle ages anymore.

eurofox

[LukeW]

want to understand how those parts are connected and how magnetron is powered

There is a good description of how the magnetron is powered in a typical microwave oven, typical voltages and what the voltage doubler does.

http://www.microtechfactoryservice.com/doubler.html

If you ignore the magnetic field and the physics of how the magnetron is generating RF from the electron cloud, you can basically just think of it as a thermionic vacuum-tube diode.

Also note the filament heater winding coming off the transformer.
A typical microwave oven transformer will have the terminals for the primary winding, a distinct HV heavily insulated winding coming from one side of the secondary, probably no wire for the other side of the secondary (tied to ground via the transformer case/core), plus another pair of wires which won't have HV insulation - these are the filament wires to the magnetron.

[SeanB]

Also every microwave oven I ever took apart has a schematic of the wiring inside the case somewhere, most commonly inside the outer case on the side where the electrics sit.

The parts shown are the capacitor, the high voltage diode, and the transformer has the heater winding as the few turns of well insulated wire, as it runs at 2kV from the voltage doubler.

[TerraHertz]

I don't think Russians are too welcome in Ukraine right now, particularly heavily armed Russians.

Really depends which part of Ukraine you mean. Most of Eastern Ukraine seems quite disappointed they didn't get Russian heavy armored support.

And that quadrotor video is a fake - there's no way it could lift that sort of payload.

Here's a lady who would disagree with you:

[nctnico]

They lost, the judge actually called them idiots.

Because they are!

I would call it lack of education. If you ever are having breakfast in a hotel you can observe how many people have no clue on how to operate the bread toaster.

[Artlav]

Naturally they took the manufacturer to court because nowhere in the instructions did it say 'do not remove the door and replace it with a metal plate'. They lost, the judge actually called them idiots.

[eneuro]

If you ignore the magnetic field and the physics of how the magnetron is generating RF from the electron cloud, you can basically just think of it as a thermionic vacuum-tube diode.

According to schematics from link you provided

there is also 5kV 700mA fuse between transformer high voltage windings and HV capacitor, so when capacitor or diode shorts circuit to ground it breaks I guess


It looks like there is nice HV charge pump with DC powering magnetron, but its inputs polarity does matter?
There are no +/- marks on its inputs and is also powered by AC those few turns from transformer in the middle, so while it heats up some kind of resistance inside magentron input, HV is between this heated element and ground, so of course those a few turns have to be well isolated, but it does not matter how this HV connector is attached to magnetron? 


One of last unknowns I think is what happends if on transformer primary we provide shifted in phase 230VAC voltage eg. using triac, so there can be voltage smaller in peak value than 325V in the case of 230VAC input, lets say at the end of 50Hz half wave 2.5ms before next zero crossing so 135 degs in phase 0.7Vmax, around 230V, so if we provide such pulses we get in this charge pump voltage doubler 4kV 70% of its available maximum voltage to magnetron if it were no phase shifts and only turning on/off transformer input-does magetron can run on lower DC voltage than those 5.6kV applied to its voltage cathode and still output 2.45GHz RF?
I mean pulses also 50Hz or 60Hz, but shorter shifted in phase between 90-180 degrees, so at lower voltage maximum than normal 230VAC so between 0V-325Vmax transformer primary input.
Which is minimum operating voltage of magnetron, also there might be temperature limit so some time needed to heat up ?
So, general question is how do they make variable microwave oven output power-by changing its pulses length or simpy turn on/off for a given amount of 20ms periods (group driving), while I do not expect H bridge driving of rectified 230VAC mains there- I saw a few relays on electronics board I guess, but do not examined it so far...

More detailed magnetron specs needed I think to predict what happends when we provide lower than nominal volateges 

[Zero999]

It looks like there is nice HV charge pump with DC powering magnetron, but its inputs polarity does matter?
There are no +/- marks on its inputs and is also powered by AC those few turns from transformer in the middle, so while it heats up some kind of resistance inside magentron input, HV is between this heated element and ground, so of course those a few turns have to be well isolated, but it does not matter how this HV connector is attached to magnetron? 

1) Polarity is important. To understand this properly, look up how the cavity magnetron works.

2) Of course, the filament is just a heater and is resistive so AC is fine.

One of last unknowns I think is what happends if on transformer primary we provide shifted in phase 230VAC voltage eg. using triac, so there can be voltage smaller in peak value than 325V in the case of 230VAC input, lets say at the end of 50Hz half wave 2.5ms before next zero crossing so 135 degs in phase 0.7Vmax, around 230V, so if we provide such pulses we get in this charge pump voltage doubler 4kV 70% of its available maximum voltage to magnetron if it were no phase shifts and only turning on/off transformer input-does magetron can run on lower DC voltage than those 5.6kV applied to its voltage cathode and still output 2.45GHz RF?
I mean pulses also 50Hz or 60Hz, but shorter shifted in phase between 90-180 degrees, so at lower voltage maximum than normal 230VAC so between 0V-325Vmax transformer primary input.
Which is minimum operating voltage of magnetron, also there might be temperature limit so some time needed to heat up ?
So, general question is how do they make variable microwave oven output power-by changing its pulses length or simpy turn on/off for a given amount of 20ms periods (group driving), while I do not expect H bridge driving of rectified 230VAC mains there- I saw a few relays on electronics board I guess, but do not examined it so far...

I believe the magnetron has a negative resistance, like a neon lamp, so the current needs to be limited. In this case the reactance of the capacitor ion the voltage double will limit the current quite nicely.

Reducing the supply voltage will probably reduce the current to a point when the magnetron fails to oscillate and the frequency could also be affected. As the filament is also powered from the same transformer, I'd suspect this would happen sooner because it would become too cool to emit electrons properly.

The power output is reduced by pulse width modulating the input to the transformer at a very low frequency. Some newer microwaves replace the large transformer with an inverter and rectifier, thus forming a switched mode power supply and the power can be more efficiently regulated by either reducing the current or higher frequency PWM.

[nctnico]

I'm wondering: would it be possible to hack a magnetron from a microwave into a transmitter for Wifi? I guess not but maybe someone went ahead and tried it anyway. Or would a pulsed radar be the best use besides wrecking stuff and cooking food?

[SeanB]

Modulating it at WiFi data rates would be difficult, way too much capacitance in the inside of the shielded case from the RF filtering for a start, and most microwave oven magnetrons are pretty poor at starting up, they tend to draw low current until the critical level is reached and the cavities start to resonate, then it takes a few cycles more for them to build up to full power. You will not notice a few extra microseconds of start time, but your wifi will. With 50/60Hz modulation it is not going to make a difference over a cycle.

Using a TR switch that will handle the full power output to reduce this will also have issues. there is a reason RADAR transmitters monitor the pulse output and use that to start a range scan, it does vary slightly and gives jitter.

[eneuro]

1) Polarity is important. To understand this properly, look up how the cavity magnetron works.

I do not mean reversing grounding with this HV positive magnetron DC voltage connector

While filnament heating is about 3VAC it does not change too much 4.6KVDC on one of those connector pins, so I guess it does not matter how those 2 magnetron positive pins are plugged-simply do not remember in which position it was connected, and while do not planned use this microwave oven again, disconnected it and forgot for a few months, happy with quite solid transformer which can be reused if one of SECONDARY HV wire disconnected from its case-else one can have 2.3kV on transformer case 
I've disconnected it from transformer case and soldered another connector, so now I've 2.3kV transformer secondary isolated from its core, so one have to be carefull if wants to reuse this transformer if not removeing completly its HV secondary 

This is one of found schematics of microwave oven circuit from web- two pins positive HV voltage  connector marked on the bottom with circle red.

There is no +/- marks on this magnetron connector-DC ground is on magnetron case and is connected with grounded HV transformer secondary and a few wires in the middle for filnament heating  in oryginal design.

Some newer microwaves replace the large transformer with an inverter and rectifier, thus forming a switched mode power supply and the power can be more efficiently regulated by either reducing the current or higher frequency PWM.

Maybe replacement of the transformer not needed in DIY microwave oven, but by adding H bridge after rectified AC mains change those pulses of corse remember about possible transformer primary designed for 50Hz/60Hz so maybe core saturation issues when trying to drive it in strange ways without AC full cycles 
Just finishing other pulse spot welder project where  also transformer is used and similar challenges, so it looks like oryginal microwave oven control electronics can be replaced by similar circuit to be able maybe better drive magnetron, but with completly closed waveguides (no windows like in oryginal microwave).
Idea is to put something to heat-for example etched PCB in temperature resistive glass and fine tune magnetron to deliver amount of power needed to heat up etched PCB copper to required temperatures 40*C-50*C.
It could be used to heat other things too if we could quite acurate control magnetron output power in clossed (no RF emissions ) waveguided microwave oven. Additionaly thermaly insulated environment, so calculate amount of power deliver and feed back gained temperature for fine control.

[amyk]

The same guy now playing with another type of "death ray"
? ? ! ??. ? ?? ??