Microwaves and electronic circuits

Discussion in 'General Electronics Chat' started by Roto, Aug 29, 2011.

  1. Roto

    Thread Starter New Member

    Jul 13, 2011
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    Hi Folks,

    I know that microwaves can fry a circuit board when the board is powered up. I've seen a recent article about "high speed police chases being a thing of the past" due to a new device that can be pointed at a car and create a voltage surge in the on board electronics.
    Can a similar microwave emitter destroy a circuit board eg. the mother board in a PC if the board is not being powered. Additionally (if the answer is no for the micro processing chips) would electrolyte capacitors (without metal jacketing) last very long given that they have a wet interior?
     
  2. Robert.Adams

    Active Member

    Feb 16, 2010
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    Can you post a link to the article regarding these devices? I've never heard of such a thing but I can only imagine that the power required for a long distance microwave weapon like that would be hazardous to human health.
     
  3. debjit625

    Well-Known Member

    Apr 17, 2010
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    Long ago I saw that on Discovery channel, it was an experimental project, I missed much of the part but I saw its affecting car's electronics to stop electronic ignition circuit mainly.But don't know how it works actually...

    For criminals go for cycles
     
  4. Robert.Adams

    Active Member

    Feb 16, 2010
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  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Well that's something different. With an EMP it could work. Although I'm not convinced that they would only stop the car they want to stop, but everything nearby, especially unshielded electronic devices.

    Somehow I doubt that it will be possible with microwaves, as they would have to be very powerful to find their way into the car electronics.

    What does exist is this: http://en.wikipedia.org/wiki/Active_Denial_System
     
  6. Robert.Adams

    Active Member

    Feb 16, 2010
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    I think pop sci was guilty of utilizing attention-grabbing vocab to describe the weapon. Technology Review describes something developed by the same company that uses pulses of microwave radiation. The system demoed has various issues, including the current prototype working at 15meters as well as my concerns about human health.

    They also say it could inadvertently mess up other systems if deployed in police applications. The TR article is much better and goes into the power and some basic circuit topologies of it.

    The concerns about human health seem to mirror that of the ADS that praondevou posted.
     
  7. PackratKing

    Well-Known Member

    Jul 13, 2008
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    It is possible.....trust me .............:D microwaves can be "reassigned" to any number of functions.

    .....microwaves can be "aimed" in a very tight "beam" over remarkable distance..........and do similar dirtywork, not unlike the damage to a 100Mw handy-talky in direct proximity to a 50 watt base station...........No concern for elevation or windage.
     
    Last edited: Sep 2, 2011
  8. Roto

    Thread Starter New Member

    Jul 13, 2011
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    I'm not sure this is the same thing I found originally. Can't exactly remember the search words I was using at the time.

    http://eurekaaerospace.com/news/fox-11-news-pursuit-stoppers

    But at the time I was wondering how a microwave pulse could work given that most cars are made of steel I thought that it must be powerful enough to bounce a tight beam off the pavement and into the engine compartment. This video seems to confirm that. The original article I read also mentioned that even the fuel pumps have microprocessors on board. It would seem that no one is able to answer my original question so some time in the next week or so I will take one of my PIC chips and add an electrolyte capacitor to the circuit, perhaps a simple charge and discharge arrangement that measures the time, and see if it still works after I stick it in the microwave, for various lengths of time, and power it up again. I doubt the cap will last very long (even if the PIC does) but I need to get a number (seconds of survival) for a device I'm working on.
    I'll post the result but I kind of doubt that anyone else really has a need to know the outcome.

    Roto
    http://www.coldgold.rotoquad.com
     
    Last edited: Aug 30, 2011
  9. debe

    Well-Known Member

    Sep 21, 2010
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    I can tell you now the chip wont survive in a microwave at all, as the energy is concentrated in a tuned cavity & will absolutly cookit.
     
  10. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Don't bother doing this. Go to youtube and search for "is it a good idea to microwave this". They did it all, cellphones, TV-sets, playstation. Result: In general it is not a good idea to microwave any electronic device.

    The real question is, how powerful the transmitter would have to be to infer with any electronic device in a car, as you said they are made of steel in general. Additionally, the electronics in a car a generally shielded. So if I aim a few kW or MW transmitter at a car, what happens to the driver, especially his eyes, even if it's for a few us/ms?

    An EMP sounds more feasible, since it generates all kinds of frequencies...
     
  11. Roto

    Thread Starter New Member

    Jul 13, 2011
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    "is it a good idea to microwave this"

    Interesting videos but I still need to do the experiment. We are just trying to determine if electronics that are OFF need to be removed from the area of interest. Exposure would be brief and at a lower intensity. The internal temperature of a cap would not get to more than about 140f.
    Wish I could say more but the thing I'm working on is just now going to a patent attorney.

    Roto
    http://www.coldgold.rotoquad.com
     
  12. Jotto

    Member

    Apr 1, 2011
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    Microwave is line of sight. So elevation will play a part. Mircowave also produces all frequencies. They have massive side lobes, even when surpressed.

    Would you use a parabolic or cosecant squared for transmitting? Could this be done, yes but the dangers involved would be to much for the average person.

    Raytheon produced the first commerical microwave, it cooked roast beef in like 15 seconds.
     
  13. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I don't think a microwave oscillator/generator can be compared to an EMP. Microwave generators have a peak frequency, like in a magnetron, the device is tuned/build to oscillate at a certain frequency. Yes they may not be stable, however, an EMP is produced by an uncontrolled reaction, like in bombs or exploding wires, no control whatsoever on the frequency generated.
     
  14. Jotto

    Member

    Apr 1, 2011
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    Yes it does have peek Frequency of 9375Mhz. With side lobe supression its a little less then half of the main freqency. 20-30kw is a lot of power for a unit operating at 70kw.
     
  15. Roto

    Thread Starter New Member

    Jul 13, 2011
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    For some reason I did not see my previous post so I wrote this one (below) which is almost a duplicate of the previous, thinking that the last one didn't get posted. So as it was to late to delete the previous I've added this preamble. But again I have no interest in stopping cars! And yes I started looking at EMP units as well as Klystron devices to see if they might be more useful than a magnetron for what I'm working on.
    --------------------------------------------------------------------------------------------------------------------

    "is it a good idea to microwave this"

    Interesting videos but I still have to do the experiment.
    I wish I could say exactly why we need to know the answer to this but the application is just going to a patent attorney to file.
    We only need to know if an electronic device (PC or Mac etc.) can withstand a brief exposure at a lower intensity than inside a microwave oven. The caps will not get to an internal temperature of more than about 140f or so and as I said the circuits in question will be OFF. In any case it will only require a little more work to protect or remove the electronics.
    Anyway thanks for the replies and it was fun watching some of the videos.

    Roto
    http://www.coldgold.rotoquad.com
    Anyone need a 4 wheel drive boat or a gold machine and yes I know the induction heating link no longer exists.
     
    Last edited: Aug 31, 2011
  16. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    How are you going to test it at "lower intensity as in a microwave oven" in a microwave oven.
    The magnetron is switched on/off every half cycle (if it's not the inverter type), and there is no regulation to it's power, it's on or off. Unless you do some modifications to your microwave oven you will apply full power to your DUT. They "regulate" the power by turning the magnetron on or off in intervals.
    Also, the magnetron in a microwave oven works at 2.45GHz, the "car stopping device" could work at any other microwave frequency.....
     
  17. Roto

    Thread Starter New Member

    Jul 13, 2011
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    As I said I have no interest in stopping cars. The microwave part of our new device will be built from a disassembled oven and reconfigured.
     
    Last edited: Sep 1, 2011
  18. debe

    Well-Known Member

    Sep 21, 2010
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    I hope you have a healthy respect for microwave oven powersupplies. These have a more permanent effect on life than microwave energy & mutch quicker.:eek: I used to repair radars & microwave ovens, The humble microwave ovens powersupply deserves Respect!
     
  19. PackratKing

    Well-Known Member

    Jul 13, 2008
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    MWO Powersupplies are every bit as lethal as mentioned > consider also:

    Unbridled microwaves from a magnetron in open-air, will cook you in short order.

    It may not get to a point of uncomfortable heat until it is too late. The damage is also cumulative.

    Eyes do not like this one little bit, and you only get two.
     
    Last edited: Sep 2, 2011
  20. Wendy

    Moderator

    Mar 24, 2008
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    Thought that occurs to me is the innocent cars that will also get fried. Will the police take responsibility, or are civilians just going to have to eat the cost?

    I remember the model rocket engine power cars, the duration and aiming is just not good enough.

    The health concerns also strike me as on target. Microwaves make dandy weapons.

    I remember a true story about one of the line men on the runway, I don't remember their official name, who was guiding a bomber with light batons. The pilot had left his RADAR on, the guy on the runway dropped dead.
     
    Last edited: Sep 2, 2011
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