Diy PEMF High Gauss

Thread Starter

Ristocrat

Joined May 9, 2021
7
I want to build a High power PEMF machine.

I have a basic understand of circuits i have been an Electrician for 6 Years but also interested in Electronics.

I'm having a few issues understanding the best design to start with

I'm pretty sure a good method would be building a capacitive discharge circuit.

I am aiming for a adjustable 0.7 - 1.5 Tesla pulse power.

Because the Tesla rating i want is quite high i think the best method for pulsing would be a spark gap.

I am not keen on using a sparkplug.

I would rather something less crude but couldn't find anything.

I am not sure whether going into either higher voltages or chunkier capacitor bank is the best direction for the power output i want




- What would be the best voltage to run a circuit like this at ?

- Is there a solid state switch that can handle switching the discharge current from a capacitor bank ?

- Are there any premade modules that are designed for spark gaps in a vacuum that are long lasting ?

- What type of capacitor would fit a circuit like this ?





The Tesla rating from what i know is affected by

Amount of turns - I am trying to go for a low amount of turns on the coil around 4

Size - I am trying to go for a large loop 30cm

Discharge current

I thought voltage would matter but the formulas i have been looking at don't include voltage

I am not really bothered by accurately calculating the Tesla rating but i would like to have a rough idea to work with


The photo i added is the type of coil i want to mimic.

Thanks,
Ristocrat
 

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MisterBill2

Joined Jan 23, 2018
8,745
OK, please explain what is a "PEMF" machine and what is it supposed to do for a person. If it is a legitimate medical device then there should be a fair amount of literature available.
What you need to do is first know the intensity of the desired magnetic field, then, for the desired area of that field intensity, calculate the amp-turns. At that point, if you have the number of turns selected, you can know the amos and the time, and then you need to calculate the inductance and the resistance. Then you will know the voltage and the current.
I really do not recommend a spark gap for switching, there are SCR devices available for many levels of current.
 

Thread Starter

Ristocrat

Joined May 9, 2021
7
The PEMF stands for Pulsed electromagnetic field therapy.

I believe it is a legitimate medical device just not commonly used, its used for horses and used in physiotherapy, chiropractors

What websites would i be able to search for literature ?

These devices are expensive around $10-$20K and one of the units i was looking at had a spark chamber which makes me think it might be for creating a high power and quick discharge ?

I was aiming for variable field intensity 0.07 - 1.5 Tesla

Desired Magnetic field - 1.5T

Desired area of field intensity - Center of coil

Calculate the amp-turns - 4 turns

Size of coil - 30cm

Is there a formula i can use for the Tesla calculation i have looking through different websites and some are more detailed and some only have 3 entries
 

DickCappels

Joined Aug 21, 2008
7,426
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2670735/

The NIH seems to think there might be something to this.

You mentioned 0.5 T but it seems like fields more like hundreds of uT are commonly used and might be easier to make and operate reliably. When it comes to medical therapy devices, bigger does not necessarily mean better.

There is one circuit idea in post #1 of this thread:
https://forum.allaboutcircuits.com/threads/scr-for-charging-discharging-capacitor-for-pemf.137203/


I searched Google with the term PEMF circuit and the image results came up a whole lot of circuits.
https://www.google.com/search?q=PEM...WTVc0KHSAfBBAQ_AUoAXoECAEQAw&biw=1600&bih=747
 

Thread Starter

Ristocrat

Joined May 9, 2021
7
The power rating is something that varies between devices, i have been following the idea that the lower power versions use difference frequencies for different parts of the body. I am trying to build what they call a Ringer PEMF which is basically not requiring to worry about frequencies just a high powered pulse to treat an area.

I am pretty firm on the idea of 0.5 Tesla some of the more expensive models go up to 2 Tesla.

I have seen a few of those circuits but they seem to be for the more lower powered output.

At the moment i think i need to work from the coil backwards which i have found a website for calculating

https://www.accelinstruments.com/Magnetic/Magnetic-field-calculator.html

Is this math the type i need for that calculation ?


Coil Inner Radius (mm): 150mm
Coil Lenghth (mm): 20mm
Copper Wire Diameter with Insulation(mm) : 8mm
Copper Wire Diameter without Insulation(mm) : 6mm ( Over heating can be an issue i might go thicker )
Number of Turns: 4
Coil Current (A):
30000A
Frequency (kHz): 1 ( i think ? )
Distance from center (mm): 0mm
Core Relative Permeability, k: 1 ( Air core )
Winding Compac-Factor: 0.9 ( not sure ? )


Magnetic Field (mT): 492 mT

Coil Height(mm): 11.52 mm
DC Resistance (Ohm): 0.002 Ohm
Inductance (uH): 9.942 uH
Total Impedance (Ohm): 0.063 Ohm



Minimum DC Driver Voltge Requried (V): 68.449 V
Resonance Capacitor Capacitance (nF): 2547842.02075 nF
Resonance Capacitor Voltage Rating (kV): 1.874 kV
DC Power Dissipation (W): 2053480.74 W
AC Power Dissipation (W): 1623674.46 W


I am not sure if all of the results from that calculator matter i was only going to follow the coil current and try and work that into what capacitor bank i would need
 
Last edited:

DickCappels

Joined Aug 21, 2008
7,426
Am I reading that correctly: AC Power Dissipation 1.6 Megawatts? Use adequate precautions so that you don't become part of that circuit.

I am an advocate of starting out small and simple. Since you have not made one of these in the past you are probably going to discover things as you develop the circuit. Getting experience with a scaled down version means you will be replacing less expensive components as you go. Another lower risk approach is to copy a known-good design.

I am not familiar with the math for such an application so I can't comment other than to gasp at the numbers in awe.

68 volts isn't going to be firing any spark gaps but you can probably use a LARGE SCR to complete the circuit.
 

MisterBill2

Joined Jan 23, 2018
8,745
It comes to mind that the action is quite similar to a capacitor-discharge ignition package that had a lot of automotive use. Those systems would be able to dump a fair amount of current through an automotive ignition coil primary up to a few thousand times per minute. So there might be a source of most of the system you seek. Just substitute your coil for the automotive coil, and add an external trigger pulse generator to simulate the breaker points.
 

Thread Starter

Ristocrat

Joined May 9, 2021
7
The idea of becoming part of the circuits scares me quite a bit, even if i don't have physical contact with conductor i would be worried using it would cause some damage through inducing my body. The last picture i linked that machine costs $9k which is why i have been trying to build my own.

I am beginning agree with the idea of starting small, the SCR would a thyristor be a good option i remember reading they are good for dumping high current loads quickly. Would the spiking current from capacitors cause issues for a SCR ?
 

Thread Starter

Ristocrat

Joined May 9, 2021
7
I watched videos of Bigclive bringing up circuits on them and i didn't think it would have enough power to give the Tesla i wanted to aim for.

I was a bit worried with going into higher powers with higher voltages on the circuit he dissects the pulse happens on the primary side of a high voltage transformer and with a big capacitor bank pulsing the primary of a high voltage transformer i worry would could happen in the case of a fault.

Before i was looking into getting a neon sign transformer 3kv and using HV diodes making bridge rectifier and charging a capacitor bank with a spark plug in series with coil

- This guy wraps a chain around coil and has the sparks flying off but i don't know if its safe because they have safety features controlling output
 
Last edited:

MisterBill2

Joined Jan 23, 2018
8,745
Many spark plugs are resistor types and will not pass much current. Also, a spark gap is not the best way to switch high voltage. Consider now that there are a whole lot of tried and proven CD ignition system circuits available, and they run on 12 volts DC, with much less shock hazard from the power source.
 

DickCappels

Joined Aug 21, 2008
7,426
$9K I wonder how I can get a piece of that business : -)

The idea of becoming part of the circuits scares me quite a bit, even if i don't have physical contact with conductor i would be worried using it would cause some damage through inducing my body. The last picture i linked that machine costs $9k which is why i have been trying to build my own.

I am beginning agree with the idea of starting small, the SCR would a thyristor be a good option i remember reading they are good for dumping high current loads quickly. Would the spiking current from capacitors cause issues for a SCR ?
An SCR is one kind of thyristor. Since you will be dumping DC the SCR will probably give you more bang for your buck.

About 25 years ago I was amusing myself by using an SCR to dump a fine low ESR tantilum capacitor into a small transformer and enjoying seeing hundreds of amps in the secondary. Then it stopped working. The SCR had killed the capacitor. Both the capacitor and SCR have to be rated to handle the peak current. If pulsed frequently, you need to take the heating effects of the average current into account too.
 
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