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Motor as switch (dc transformer)

  1. Nov 2, 2007 #1
    here's an idea i just came up with, it's to run DC into the primary of a tranformer and get a constant output: place a brush motor (like the ones in model airplanes/cars) in series with the primary coil, the motor will spin(obviously) and act as a switch(as the brushes swap contacts) so there will be fluctuation with the field induced into the secondary coil so there SHOULD be a constant DC output. Although, it would probably resemble monopolar AC... would it be considered monopolar AC?
    just a thought...
    ill go try it out...
     
  2. jcsd
  3. Nov 2, 2007 #2

    stewartcs

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    Well I'm not an EE so keep that in mind, but I would think (assuming the brush motor gives a pulsed output to the primary of the transformer like you desire) that the output of the transformer (assuming it is ideal) would give you a square wave output as well.

    I believe it (DC transformer model) is the principle on which DC/DC converters are designed. Not sure though.
     
  4. Nov 2, 2007 #3

    dlgoff

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    If you have the parts, try it. But you won't get dc on the secondary winding of the transformer.
     
  5. Nov 3, 2007 #4
    So it would be monopolar AC then? interesting....i kinda want to test this with my NST...
    ofcourse, if this is monopolar AC this is still way useless compared to an inverter except for the much higher frequency....

    idea for practical use:hook up transformer/rectifier to mains, add a smoothing capacitor to rectifier and add this set up. the result would be a frequency step-up-er thing(i think)
     
  6. Nov 3, 2007 #5
    bleh, i tried it, didnt work. this is quite odd though because with 300vDC i can get a CONSTANT arc of about 0.3mm or so when i place the motor in series with the spark gap but when i replace the spark gap with my NST i only get an arc off my secondary for a split second, as if i had merely connected it straight to a battery.
    power supply is a rectified 300v transformer, unsure or its other ratings(amps etc) i could probably try to work it out mathematically but i highly doubt my transformer is 100% efficient and the ratings really shouldnt make much diff anyways...
    any ideas why this is working with a sparkgap if it doesnt with a transformer? i should assume that the reason im getting a constant arc across the gap is because my motor really is acting as a switch but then i dont see why it cant fluctuate inductance in the nst and give me a constant arc on my secondary.
     
  7. Nov 3, 2007 #6

    dlgoff

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    Wait, wait. I didn't know you were going to be messing with mains. I would discourage this. Just work with battery voltages untill you get a little more knowledge. AC mains can kill you and at the least give nasty burns.
     
  8. Nov 4, 2007 #7
    Dont worry, i been "messing" with the mains for years now... i know what im doing. i know my my name on here is tc_kid but i assure you im not some ten year old... im sixteen, which yes i know is still extremely young and inexperienced compared to nearly everyone here but ive been into electrical and aeronautical engineering since, well forever i suppose... i started high voltage experiments when i was 10, i built my first tesla coil(hence the name tc_kid) when i was 11 and since then ive dealt with voltages exceeding 500kv on nearly a daily basis. and, ive always used the main as a supply to all my experiments... my bedroom is practically a lab in itself and i use it every day... im far from inexperienced... ofcourse, i dont claim to know everything which is why im still asking questions and for advice and all, i come up with such ideas and questions because i want more knowledge...
     
  9. Nov 4, 2007 #8
    You are dancing with the devil, kid.

    Maybe you have been doing it for years, but one wrong move and you're toast. Get the proper equipment
     
  10. Nov 4, 2007 #9
    10 ft away with a faraday cage seems safe enough to me...
    ok, fair enough, i wasnt using a faraday cage to isolate this motor thing, it didnt seem that threatening to be honest but i do use one for MOST of my HV stuff(this is not hv though, its 300v).
    still, all my wires are insulated, i use proper rf grounding, i stay a fair distance away, i keep my hand off the switch as much as possible, i always wear rubber soled shoes, i make sure all my capacitors are discharged before touching anything and i have an alarming amount of stuff you may mistake for russian military property(actually, i used to have some old 20kv doorknob caps from one of their subs).

    so yes, i do have proper equiptment(i get it mostly second hand from industial parks) and i think im taking all the neccessary safety measures. if i should be doing(or not doing) anything else though please tell me...
     
  11. Nov 4, 2007 #10
    anyways, based on my 3rd post in this thread(5th post in it all together) does anyone know whats going on and why it doesnt work with the transformer when there is a contant arc across the spark gap? is the motor really acting as a switch?
     
  12. Nov 4, 2007 #11

    stewartcs

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    300 V is indeed considered high voltage...Becareful.
     
  13. Nov 4, 2007 #12

    stewartcs

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    Hook an oscilloscope up to it and look at the waveform...what does it look like?
     
  14. Nov 4, 2007 #13

    stewartcs

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    BTW, you will probably have to scale it down to whatever the O-scope can handle.
     
  15. Nov 5, 2007 #14
    damn, the one piece of equiptment i dont have, been wanting to get an o-scope for ages but i just havent got the cash...

    i do have an o-scope programme in my computer however but i cant figure out how to start the bloody programme... its like a proper o-scope only without the "on" switch...
    i cant remember the exact name of the programme or where i got it from but its titled"oscilloMeter" on my desktop, it came with a sound generator and a SF-16 controller2.0, if anyone else knows what im talking about and has the same programme could you please tell me how to start it


    (i guess with all the solidstate stuff these days 300v would be considered high but im more of an analogue person and 300v is not too high compared to most of my stuff, esp. my 300kv tesla coil... so yes i guess its high but it doesnt really seem like it in contrast. ofcourse, with all the energy loss and current transormation that also goes on the total power of my HV stuff has got to be lower than it is straight out of the mains... i doubt my tc is more than a fraction of a milliamp)
     
  16. Nov 5, 2007 #15
    dont worry, im not ignoring your advice, im most definately taking heed of it...
    (BEING CAREFUL......)
     
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