Pulsed electromagnetic field therapy (PEMF therapy), also known as low field magnetic stimulation (LFMS) uses electromagnetic fields in an attempt to heal non-union fractures and depression. In addition, PEMF therapy improves sleep, mental focus, and the body’s overall performance by helping the energy output and regeneration of the body’s cells.
Commercial such devices are sold at a price of several hundred to thousands of dollars, so my goal is to make the simple to build and functional device available to more people who can not afford it. This time I will show you a simplest way to make a PEMF device, which gives a magnetic flux density of about 10 to15 Gauss.
The device consists of several components:
- ZK-PP2K High power PWM driver
- 12V to 19v Pover supply unit
- some type of connector to which the coil would be connected
- and the therapeutic coil
The heart of the device is this small module ZK-PP2K which can be purchased for less than 5 dollars. This small package contains a power output transistor so that the coil is connected directly to it. All we have to do is connect a 12 to 19 volt power supply with a power of 50 watts or more. This means that can be used power supply from an old PC (12 Volts), or a Laptop (19 Volts).
We need to pay attention when making the coil because the normal operation of the device depends on it. When making it, we need to adhere to several conditions:
- The ohmic resistance of the coil must not be less than 6 Ohms with 12V power supply, and 9 Ohms with 19V supply. At lower than these resistances, mosfet damage can occur. This resistance depends on the thickness of the wire, the number of turns and the diameter of the coil.
The coil inductance should be greater than a few millihenry. You can use one of the online calculators for calculations, such as: https://www.66pacific.com/calculators/coil-inductance-calculator.aspx
For example, I will introduce you to the dimensions and characteristics of two coils:
The first is the simplest example and is actually the primary winding of an E-type transformer with a power of 150 watts, to which the metal core has been removed. It consists of approximately 400 windings of copper insulated wire with a diameter of 0.4 mm. Its ohmic resistance is 16 ohms and its inductance is 10 mH.
The next coil was made by me and has a diameter of 17 centimeters. Contains 180 windings of insulated copper wire with a diameter of 0.45 mm. Its ohmic resistance is 12 ohms, and the inductance is about 5 mH.
In any case, the construction of the coil is not critical as long as we adhere to the rule that its ohmic resistance is greater than the minimum as stated above.
Based on the instructions of many manufacturers of such devices, this frequency should be in the range of 4 to 30 Hz and a duty cycle with a value of 5% to 15%. In this case frequency is 13 Hertz and Duty cucle of 10 Percents
I am not a medical expert and I can not discuss the effect of the device, although I personally have many positive experiences from using it. I can also say with certainty that low frequency magnetic fields definitely have no negative impact, except in people where it is contraindicated(Pregnancy, Pacemakers, bleeding, Active tuberculosis, Malignancies). In fact, MRI imaging uses magnetic fields that are tens thousands of times stronger than those at PEMF, and as we know this type of diagnostics is completely harmless.
Finally, the device is mounted in a suitable plastic box.