PEMF Project

Discussion in 'The Projects Forum' started by Rittter, Dec 6, 2015.

  1. Rittter

    Thread Starter New Member

    Dec 5, 2015
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    I am using a cheap function generator to pulse a coil. I am using a square wave, 12Vpp supply at 10 Hz. I have read you need to protect the circuit using a diode because of flyback voltage. I tested an LED for this purpose. It lit up applying current to both the cathode and anode. Is this because of the square wave, and what would be the best component to use ?
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    You need a fast diode like 1N4148, , or 1N4001/7 series
     
  3. Rittter

    Thread Starter New Member

    Dec 5, 2015
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    Thank You !
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,028
    3,237
    Does the output of the function generator go negative?
    If so you need two diodes to avoid shorting the generator during the negative voltage excursion.
    Put one diode in series with the output of the generator (anode to generator) and the other across the coil (cathode to positive side).
     
  5. Rittter

    Thread Starter New Member

    Dec 5, 2015
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    Thank you for your input. No, it does not go negative. But what I plan to do next might do just that. Presently, I am working with three pre-manufactured coils which I don't know their exact construction. They are circular, 9" in diameter, 1/4" thick, with a resistance of 125 Ohms, and an inductance of 135mH. I plan to construct another coil to be positioned on the interior of the present coil and wiring it to the existing 9" coil, with the current to travel through the existing coil first then through the new coil, which should have nearly zero resistance.
     
  6. Rittter

    Thread Starter New Member

    Dec 5, 2015
    21
    0
    One more observation: I am in the process of obtaining parts and have stopped using the function generator. With my present set up, I found the generator is getting very warm after 20-30 min. of operation. Is this typical of a generator, or could this be the result of fly back voltage ? Again, I am operating it at 10Hz-100Hz., 27-13 VDC while pulsing a coil.
     
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