Microwave transformer help?--hope this is the right place

Discussion in 'General Electronics Chat' started by has91, Jan 12, 2009.

  1. has91

    Thread Starter New Member

    Jan 12, 2009
    Hi. I’m doing a science project in high school, in which I dismantled a microwave, and took the microwave magnetron, capacitor (no need to worry; the capacitor was discharged) and transformer out.

    Before I go on, the premise of the project was to get a magnetron to emit a microwave, which would be received by a rectenna (composed of an isolated microwave antenna—in this case a wi-fi antenna, connected by wire to a Schottky diode) which rectifies the AC current and turns it into DC current. In other words, wireless power transmission.

    Now, I’m particularly having trouble with the transformer. I’m planning to hook up the apparatus to a variable power supply, in which in the science classroom, has an outlet that you can put wires into. One hole is for positive current, another is for negative current.
    The variable power supply is in one room, the outlet for the two holes is in another.

    This poses a problem, as I have a normal electrical plug (you know, for common household electrical outlets) for the microwave (which is connected to the control board AND eventually to the transformer). The transformer is a step-up transformer. The input has two flat knobs (almost like those on an normal electrical plug), and the output has other knobs that I was able to connect to the capacitor and the magnetron via wire. I supplied the link to a diagram of the transformer at the end of this post.

    I’d like to bypass the controls and be able to directly wire the transformer to the variable power supply via the two holes (+ and -) instead of plugging it into the electrical outlet, that way I can directly control the voltage of the current going into the transformer, instead of having a steady voltage from the normal electrical outlet.

    How can I make this possible? I don’t know how to distinguish between the two input knobs on the transformer (where to plug into positive and where to plug into negative).

    I was wondering if it was possible I can use 18-gauge wire to connect into the two variable power supply holes, and connect it to the two input knobs on the transformer via alligator clips.

    Here is the link to a diagram of a transformer that is extremely similar to mine:


    Pardon me for the extremely long explanation (more info is better than less). If you have any questions for me so you can help me by all means let me know.

    I would greatly appreciate your help.


  2. jpanhalt


    Jan 18, 2008
    Sounds like the outlet may supply DC. You cannot run a transformer on DC.

  3. leftyretro

    Active Member

    Nov 25, 2008
    You sound pretty inexperienced with electronics. If you have a device that has + and - output terminals then it is a DC device (adjustable power supply perhaps?). A transformer such as the one you have from a microwave oven can only pass AC current not DC.

    Disassembly and reconstruction of a high power microwave source has both high voltage and high RF radiation hazards that can have real safety concerns for both yourself and others. This is not the kind of project one should be working with without a lot more knowledge and experience. I would hope that your lab supervisor would have given you more guidance in project selection.

  4. thingmaker3

    Retired Moderator

    May 16, 2005
    Transformers won't work on DC.

    It is extremely dangerous to experiment with the voltages needed for your experiment without first learning the basics, practicing for a thousand hours or so, and of course taking all the requisite precautions.

    Please put this experiment away until you have the knowledge and skill to perform it safely.

    Please begin here instead: http://www.allaboutcircuits.com/vol_1/index.html

    We will be happy to help you in your journey.
  5. SgtWookie


    Jul 17, 2007
    Please immediately cease experimentation with your project.

    The potential for grevious bodily harm to all humans and animals nearby is very real and extremely likely.

    Experimenting with high power microwave emissions can be deadly, even if you know what you're doing. High power airborne radar/missile fire control systems were my specialty in years past.

    If you really want to continue with such experiments, put your idea off until after you graduate from high school, then join the Navy, Marines, or USAF, and you will then have opportunities to train in such endeavors. Or, if you wish, you can read much of the Navy/USMC materials online:
    Complete NEETS modules 1 through 19 before attempting anything similar to what you're contemplating. I don't mean a "skim-through", either - I mean understanding all of the material.

    In the 70's, it took me nearly a year to get through the course that preceeded NEETS when I was on active duty. It then took several months more training on the systems that I would be maintaining before I was allowed to operate it without supervision.

    In electronics, safety must always be the key issue.

    Turning a conventional microwave oven inside-out (which is what you have essentially done) is inherently unsafe.
  6. eblc1388

    AAC Fanatic!

    Nov 28, 2008
    Not to mention the few thousand volts with high current on the microwave transformer secondary.

    Touch it and you are dead.

    Your tutor/teacher is obviously not knowing what you are doing or else you will be stopped immediately without a doubt.