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Varying electromagnetic field

  1. Jan 16, 2017 #1

    I am developing a setup to generate dnamic eletromagnetic fields (EMF) which will be used to study the effect of EMF on bone francture healing in small animals.The setup has two solenoid coils which are seperated by a distance and connected in series. Both coils are excited by 15 V AC that generated the EMF of 200 µT in the space between the coils. However, I want that the EMF to very between 0-200 µT repeatedly.

    Can you tell me what changes I should do in my setup?

    Thanks,

    Mit


    Pulsed electromagnetic field? - ResearchGate. Available from: https://www.researchgate.net/post/Pulsed_electromagnetic_field2 [Broken] [accessed Jan 16, 2017].
     
    Last edited by a moderator: May 8, 2017
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  3. Jan 16, 2017 #2

    berkeman

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    Welcome to the PF. :smile:

    That sounds like an interesting research project. It seems like I've seen similar research in the past, but I don't remember where. What signal generation equipment do you have available in your lab? Do you have something like an HP 33120 AFG source available?
    That link doesn't take me directly to the paper. Can you provide a direct link please?
     
    Last edited by a moderator: May 8, 2017
  4. Jan 16, 2017 #3

    berkeman

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    BTW, "EMF" traditionally means "Electromagnetic Force", not EM Field. I was a little confused by the way you used the term in your post. :smile:
     
  5. Jan 16, 2017 #4
    Thanks. Yes I should use EM field.
    First I convert 230 AC to 15 V AC using a stepdown transformer. After that it is directly feeded to the coils which gives me EM field of 200 µT. However I want EM field to be continously changing. For that I am thinking add a small pulse generator circuit between the transformer and coil. The pulse generator looks like this.

    http://www.lamja.com/?p=33

    Do you think giving 15 ´V AC as an input to this circuit can create ay problem?

    Mit

    PS: Sorry that RG post got deleted :(
     
  6. Jan 16, 2017 #5

    berkeman

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    Are you sure you just want to us a 60Hz coil drive? I would think that higher frequencies would be more effective for affecting the bone healing. What types of waveforms have been used in previous research, and how effective have they been?

    Do you have access to an electronics lab at school? Or are you just doing this at home for a personal research project? I'd guess you must be part of a lab, if you are going to be doing actual experiments on lab animals.

    An instrument like the HP 33120 Arbitrary Function Generator is a good tool for this, since you can program many different types of varying waveforms to be output. Then if you need more power, you just use an amplifier in series with the HP 33120 source...

    http://www.sglabs.it/public/SgLabs_HP_33120A_1.JPG
    SgLabs_HP_33120A_1.JPG
     
  7. Jan 16, 2017 #6

    ZapperZ

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    Actually, I'll go even one step further. What you are generating is not really an "electromagnetic field", but rather simply a "magnetic field", based on the fact that you measure a maximum of 200 μT field.

    So it seems that you want to do the same thing that a pulse NMR can do routinely. However, there are a couple of things that puzzles me:

    1. What is the pulse profile that you want? You said you want to repeatedly go between 0 - 200 μT, but you didn't describe the time profile of the pulse.

    2. Aren't you getting repeated cycle of the magnetic field already? After all, you do have an AC source that, according to you, can get to 200 μT. If you only need the magnetic field to be only in one direction, then maybe rectify the AC current.

    Zz.
     
  8. Jan 16, 2017 #7
    Square pulses of around 30-50 ms may work. Previos studies actully used same pulse width and frequency like between 10-20 Hz. So I would first like to try what has been used previsouly.
    Thanks for the suggestions HP 33120 but I want to integrate the pulse circuit in my coil assembly.

    What do you thin about LM 324 OPAMP?

    Sorry I am new to EMF field so I might be littlebit stupid speaking.

    Thanks,
     
  9. Jan 16, 2017 #8

    berkeman

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    It's a low-frequency, low-power opamp, but perhaps you could use it in your application.

    Another option would be to use your PC's sound card and free software to make a PC-based signal generator. That would give you a lot more flexibility in the waveforms you generate for your experiments. You could make a small power amp for it as well, if it looked like you needed more coil drive power. Just google Free Sound Card Signal Generator Software to see what some of your choices are. :smile:
     
  10. Jan 17, 2017 #9
    Many thanks. Just a quick question.

    Would you agree when I say, " The EM field generated by exciting coils with AC voltage is always changing since AC voltage is constantly changing".

    Thanks,
    Mit
     
  11. Jan 17, 2017 #10

    sophiecentaur

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    Yes, I should think it really would need more power. This would definitely apply if you try to operate the coils at a higher frequency. You need to have some idea of the specification of these coils you are using. If they are for 60Hz operation then they could have iron cores, which would limit the possible operating frequency. There may be markings on the coils, telling you their Inductance value.

    PS It is worth asking about the Ethics of the research you are doing. Are the animals in this experiment alive and are they being treated in an acceptable way? I'm not sure of the stance of PF on this sort of research but it is a question that needs to be asked.
     
  12. Jan 17, 2017 #11

    jasonRF

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    Agreed.

    Also, depending on where this research is done there may be requirements to comply with university or company policy. I have done some work at a university in the past where any research involving any live animals or people must be approved and monitored by a special committee. It involved explicit written protocols for the experimentation, and documentation to demonstrate compliance with established safety standards / regulations, etc.

    Jason
     
  13. Jan 17, 2017 #12
    Many thanks for valuable suggestions
     
  14. Jan 17, 2017 #13

    sophiecentaur

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    Do you have a comment about the ethics of this?
    It may be that you are, in fact, dealing with bones, in isolation.
     
  15. Jan 17, 2017 #14
    So far I was thinking that 200 µT field foe 1 hr/ day should not make any discomfort to the animal.
    Actually this information is currently for a grant application and I need to check this with the other department for the ethics about applying EM field in the animals.

    Mit
     
  16. Jan 17, 2017 #15

    sophiecentaur

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    I agree. What bothers me is breaking the animals' bones in the first place. Crack - squeak!!!!! Never mind - you'll soon be mended again.
    But your grant application will obviously be vetted for any such problem (if you are in a civilised part of the World.)
    But, returning to the EE aspect, you will need to have the parameters of the coil (which will be on record somewhere) and then come back for some ideas about the power requirements. At some stage, you will need to be getting your hands dirty with beastly electrical stuff. You will need to be measuring the current in the coil circuit and that will involve breaking into the wire and inserting an Ammeter (AC) Most DMMs can measure current up into audio frequencies.
    60Hz is way more convenient than any other frequency you might choose. (other than 50Hz in Europe etc)

    I would imagine that your grant application will need to involve fairly good estimates of fields and frequencies, based on earlier work. You could expect that, in any interview, you could be asked to provide some 'Engineering' figures. The easiest aspect of the work would be producing a source of variable frequency AC at a few Watts. That's Radio Ham stuff. and probably off the shelf in your lab, somewhere. Finding out what you actually want will be the hardest technical task.
     
  17. Jan 17, 2017 #16
    Hi,
    Thanks.
    I can understand your feeling for animals (regardless you are vegeterian or nonveg) however I am sure that you completely ignore the fact that if this method works, how much releif it can bring to older patients having factures where bone just refuse to heal and making life of the older patients miserable. You may also want to know how many animals were killed to find the vaccines which brings comfort to our life.Never mind this is not the right discussion for the forum.
    Being from the civilized contry (I think) called Germany, I am sure that I need to give a clear picture about the application I am making. I really appreciate the doubts you raised as it helped me to think more about the physic aspect of this project.
    Rearding the coil parameters, the coils have inductance of (1.5 mH) and current flowing through should be 15 Ampere. Yes now I am thinking on variable AC frequency generator.
     
  18. Jan 17, 2017 #17

    berkeman

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    I would think that by now in most developed countries, there are protocols in place for medical experiments involving lab animals. After all, as Centaur points out, you need to break the bone before you can try to heal it. It does sound like you are following protocols.
    Then you will definitely need a power amplifier. If you are doing a grant proposal, include the AFG and a power amp in your equipment list that you need to purchase.
     
  19. Jan 17, 2017 #18

    sophiecentaur

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    Hmm. That's a philosophical issue as to whether the means always justify the end. It's beyond my pay grade to decide what 'should' be done in cases like this. There are plenty of dodgy procedures using animals and they are sometimes have flimsy justification. I fully understand your feelings about this, though. You will need to abide what the 'committee' decide if you want to avoid disciplinary issues, though.
    Germany is pretty squeaky clean in this regard, I think.
     
  20. Jan 18, 2017 #19
    Thanks for suggestions..
     
  21. Jan 21, 2017 #20

    tech99

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    I do not see the justification for animal experiments because 200uT seems to be essentially safe for humans, and is the Reference Level for low frequency magnetic fields. So why resort to animal testing?
     
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