# Pulsed Magnetic Field Therapy (PMFT) Circuit

Posted on Jul 31, 2015

Here is a simple circuit based on 555 IC that generates a pulsed magnetic field. You may use this field for pulsed magnetic field therapy. Human body is influenced by natural magnetic fields such as Earth’s magnetic field, fields due to geomagnetic storms, magnets, and magnetic rocks etc. Pulsed ELF magnetic fields (PEMFs) help cells to maintain their health (energy production, removing waste, self-repair, and regeneration) and cause motion of ions and electrolytes in cells and tissues.

PEMFs remove stress, accelerate healing, and slow aging process. Stress exhausts body and lowers the cell’s membrane potential which is usually 70 to 90 mV. The cell dies if this potential drops to zero level. A cell uses 50% of its energy to maintain this potential. PEMFs help building this membrane potential. High-intensity PEMFs (very short and strong magnetic pulses like lightning) destroy cancer cells. Suggested PEMF frequencies are between 1-50 Hz.
Here is the circuit that generates pulsed magnetic fields from about 1.5 Hz to 30Hz.

Since it’s difficult to find a suitable potentiometer, I select P1=1MΩ and P2=50KΩ initially. I also assume R1=R2=2.2KΩ. C1 is calculated as 0.88µF for max f =30Hz. Four 220nF capacitors are connected in parallel to form 0.88µF. For P1=1MΩ, min f =1.5Hz. Pulse width can be adjusted from about 1.5ms to about 31.5ms using P2. Thus, it’s possible to vary duty cycle from about 5% to about 95%, for any frequency point.

The field coil is 1.6cm in radius and has 18 turns. It has an inductance of 14.3µH. Supply current is about 0.4A when duty cycle is 5%, and it’s about 4.8A when duty cycle is 95%.

Next step is to calculate the magnetic field strength. Except along the axis, the magnetic field of a circular coil cannot be expressed in closed form. Along the coil axis,...

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