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AC Polarity swapping circuit

Discussion in 'Power Electronics' started by m_alizd, Oct 2, 2019.

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  1. WHONOES

    WHONOES

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    I would say that's it's a lot of f*rting about for the sake of a few A$. The link I provided shows a completed board for A$12.5, hardly a Kings Ransom.
     
  2. m_alizd

    m_alizd

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    I spend a bit of time on this as you and Whonoes both mentioned. Just considering a typical H-Bridge with 4 SCRs and the load. That seems to be acting like rectifier and I couldn't get positive and negative cycles. From my research it turns out I should have 8 SCRs and 4 different control signals as it l Looks like I should have two SCRs in inverse parallel configuration on each of those 4 positions in H-Bridge.
    Does this seem right to you?
     
  3. m_alizd

    m_alizd

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    Oct 2, 2019
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    No. You do not build an H-bridge but the same circuit as your first one using 4 scrs instead of triacs.

    I still have absolutely no clue what you want to achieve with your scheme and why you can't use the AC as it is.
     
  5. BobK

    BobK

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    That's because he refuses to tell us what he is hoping to accomplish with this. I don't know why anyone is continuing to help.

    Bob
     
  6. WHONOES

    WHONOES

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    Tell us what you are trying to do with this project otherwise we are likely to give up as we are just taking shots in the dark
     
  7. m_alizd

    m_alizd

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    Oct 2, 2019
    I missed your questions as I was focused on exploring solutions.
    AC as it is powers up the load, but I'm hoping to get more out of it. With the output as described I'm hoping to trigger an action in load apart from it's normal operation. Let's say there is a buzzer in the load and I want to create a quick buzz sound of 100ms long. I can send a polarity swap now to start the buzzer, then another one after 100ms to toggle that.
     
    Last edited: Oct 8, 2019
  8. davenn

    davenn Moderator

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    what do you mean by that ??



    yeah OK

    ??? doesn't make sense


    Ohhh and I rejected your post report as the comments made by that person is how we all feel
    people are trying to help you but you wont tell the full story
     
  9. m_alizd

    m_alizd

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    Oct 2, 2019
    Really???
    What's the problem with it?
     
  10. davenn

    davenn Moderator

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    yeah really


    1) why do you think you need to do a polarity swap to make the buzzer buzz ?
    the buzzer will operate as soon as it gets voltage to it

    2) a bit difficult to polarity swap an AC voltage. It's polarity is already swapping 50/60 times a second


    that's why it doesn't make sense
     
  11. m_alizd

    m_alizd

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    Oct 2, 2019
    Maybe that's the gap which causes misunderstanding, and also perhaps it's needed to go through all the posts.
    I didn't mean to deliver power to buzzer directly. This would just be a trigger for a circuit that would control the buzzer, as to when to start buzzing and when to stop. Right?
     
  12. m_alizd

    m_alizd

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    Oct 2, 2019
    Well no wonder! True, that's why I have that challenge and all these discussions.

    And remember this is all a hypothesis right now, may work or may not. maybe too expensive that not worth it. But in my opinion any idea worth a thought and maybe try it if it doesn't cost a fortune
     
  13. davenn

    davenn Moderator

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    and therein lies all the problems, because you are not explaining yourself properly, everyone is just wasting time guessing at what you really want

    you need to start being clear and concise, step by step, in exactly what you want to achieve
    so far after 32 posts total in this thread, that hasn't happened

    so would you like to start again and lay out your idea clearly so that people understand and then offer you good help ?
     
  14. m_alizd

    m_alizd

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    Oct 2, 2019
    I'm not good with descriptions I might try ,

    Achieving the attached output from the input is what I want to achieve. Is there any questions in the circuit input/output?
     

    Attached Files:

    Last edited: Oct 8, 2019
  15. Harald Kapp

    Harald Kapp Moderator Moderator

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    My interpretation is:

    The load is powered by AC and may be remotely located.
    The AC power supply is going to be used for power and signalling, where signalling is to be done by the "polarity inversion" scheme.

    This surely can be achieved, but not with a very simple circuit. Also by this scheme an additional DC component will be introduced to the AC signal. This DC component may or may not cause trouble down the line - we can't say as we do not know the load.
    Power line signalling could be used. Or an inexpensive radio technology like e.g. Zigbee. Wifi, LoraW<n, you name it. Modules for this kind of radio communication are inexpensice.
     
  16. m_alizd

    m_alizd

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    Harald, your interpretation is exactly right. The load will have rectifier so DC component on AC line shouldn't be a problem.
    Thanks for the links although they look too sophisticated for me. I'd be checking H-Bridge in first step.
    I still can't understand how you think I should use SCRs in there instead of TRIACs. With SCR I only get full rectification with one polarity not both. Did you mean I use a full-rectifier before H-bridge? that's the only way I think SCRs would possibly do the job
     
    Last edited: Oct 8, 2019
  17. hevans1944

    hevans1944 Hop - AC8NS

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    So, let's get to the meat of WHY @m_alizd, Matt, with almost NO knowledge of what his "polarity inverted" AC wave forms will actually DO when applied to a load of some sort, is trying to design-to-cost (worrying about nickles and dimes as @WHONOES has intimated in his post #21) instead of designing-to-spec which is how all electrical engineering is done today. Electrical engineers don't hope their circuits will work. They design using circuits that are proven and known to work. Refinements and improvements to reduce cost, increase efficiency, and save the planet come after a design has been proven to work.

    Tinkerers might throw together components, based on some fuzzy and probably incorrect understanding of how those components actually work, but the result is unpredictable. It is not design.
    Not all ideas are worth a thought. Some ideas, like perpetual motion (energy obtained from nowhere), are not worth considering no matter how inexpensive it is to try... unless you plan on creating another Universe from Nothing, complete with a Big Bang to get the balls rolling... good luck with that. Other ideas may be worth thinking about (vacuum balloons for heavy lifting seemed promising a hundred years ago) but have very real physical limitations that have so far prevented their development, despite years of "research" and "thinking about" it.

    I think Matt woke up one morning and "discovered" an idea that will make him a fortune if built and marketed to the masses. Hence the need to pay attention to cost before a working prototype is available. It seems many so-called "inventors" get stuck in this chicken-before-the-egg trap, spending small sums of money (at first) trying to make a prototype work, then later soliciting funds from "investors" and family members and anyone else stupid enough to throw their money at ideas instead of products, hoping to reap windfall returns as soon as production and sales ramp up. Not a bad idea to fund projects that way. There are a few born every day who will gladly open their purse to funding promising, but speculative, new technology. Open a crowd-funding site to discover just who these folks are. Make promises you may or may not ever be able to deliver. Most of all, rake in some for yourself, don't get caught, and don't get arrested for fraud. Have fun, but please don't bother looking here for "answers" because you don't know how to ask the right questions.

    Here is a similar viewpoint:
    Exactly! Until you finally figure it out, that responding to Matt is a total waste of our free time (WOOFT), you should direct your efforts elsewhere.
     
  18. m_alizd

    m_alizd

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    In my opinion that should be a priority for everyone, thanks for bringing that up.
    Thanks for encouraging me to have fun, I think that's what I need it.
    I don't think it is, if not anything, now I know vacuum balloons for heavy lifting was considered as well as perpetual motion.
     
  19. davenn

    davenn Moderator

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    OK, now you have crossed the line into woo woo

    This thread is now closed
    you are welcome to make a clean start in a new thread and clearly state the objectives as this thread is just 2 pages of
    misunderstandings and guesswork that doesn't achieve anything

    NEVER ever mention PMM 's and the like again OK ?
     
    Last edited: Oct 9, 2019
    (*steve*) and hevans1944 like this.
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