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Series or parallel coils for equal resonance

  1. Sep 10, 2007 #1
    I have a 555 out put connected to a coil and i get the frequency i need.
    But now i need the 555 to power more coils. How should i connect the coils to keep the same frequency. In parallel or Series?

    The 555 will not directly power the coils. It will switch a Mosfet and that will provide the power for the coils.

    The 555 will have to work about 24/7. Can it?
    Last edited: Sep 10, 2007
  2. jcsd
  3. Sep 11, 2007 #2


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    Science Advisor
    Homework Helper

    The 555 will work for years 24/7.

    The rest of your question is not clear, but additional coils in either para;;el or series connection will change the resonance.
  4. Sep 11, 2007 #3


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    Staff: Mentor

    It sounds like you should add a buffer driver for each coil. The 555 can still generate the original signal, but you need to buffer that source to drive each coil load.
  5. Sep 11, 2007 #4
    Heres a photo of my current design.

    I took a copper wire and coiled it around 8 scerws. then when i turn it on the led on the secondary coil lights up. a.k.a IT WORKS!
    But the 555 gets hot in like a few seconds. Because this is a prototype i am not using a fet yet.

    Attached Files:

    Last edited: Sep 11, 2007
  6. Sep 17, 2007 #5
    It most likely gets hot as you are trying to source too much current from the little 555 timer. The 555 timer can source quite a bit of current for a microchip (around 200 mA usually). But you're obviously asking it to deliver more, so yes, as you say you should use the MOSFET as a buffer to the coils. The frequency of the output should depend on the RC circuit you're using with the 555 timer, this should (ideally) be independent of the impedence of the coils. Parallel connection would give you the strongest magnetic field. Just make sure your MOSFET is capable of suppying the required current.
  7. Sep 17, 2007 #6
    if i do it in parallel will i need a fet for every coil? and then have the 555 output drive each of them?
  8. Sep 18, 2007 #7
    Depends on how much current your FET can supply. But if you have a few FETs to spare, this is probably the cheapest solution.
  9. Sep 18, 2007 #8
    I have 4 SUB85N02-03-E3's. they have an Id 85
    I should have some more fet's coming on wednesday
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