Magnetic Radiation

Hi Les,

I got the impression from your question that you are using an open coil and that you are not talking about the travel of a plunger but rather the extent that the magnetic field extends radially from the coil. Is this so?

John

Hello yes this is the case i.e. from a coil and core how do I achieve the maximum range ?  Given I have limited power i.e. a 12V battery.

I think, but don't know, If I pick the right core material it will help, not sure about geometric shape.

regards

Les C

Hi Les,

Could you use a boost converter to increase the voltage above the 12V available from the battery?

Best Regards,

Rachael

Hi

a boost convertor is something I had considered jumping from 12 to 24V but if I could find another way then I would take the most cost effective / reliable way.  Do you have in mind a circuit you have used to do this ?  I have had a trawl around the net but there are so many circuits out there I cannot evaluate them all and I would like the device to be as reliable as I can make it.

Les Collier wrote:

 

Do you have in mind a circuit you have used to do this ?

12V to 24V step up is a fairly common thing to want to do so there will be lots of circuits for this around. You've not given us too much detail on your coil, how much current does it draw from your existing 12V supply? This will affect the choice of converter IC. There are lots of cheap ready made converters available if you want to try an off the shelf solution, something like this maybe just to do some initial testing: http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.X401127469617.TRS0&_nkw=401127469617&_sacat=0

Be warned, you get what you pay for and often things like this which are cheap aren't good for a reliable long term solution. Test the theory with something like this and then look for a more permanent solution after you have proof of concept.

Can you draw a diagram of what you are trying to do, or at least explain it better. Generally speaking magnetism is not a long range phenomenon (ie it's pretty weak once you are separated from the source by a distance equivalent to the size of the source, eg the flux from a solenoid is pretty low once you are 1 solenoid length away from the end.) - if we understood what you are trying to do it might be possible to help a bit better.

MK

Hi Les,

The magnetic field lines, that are being generated by a specific amount of power (Amps times Volts), are part of a magnetic circuit that by convention comes out of the north pole and loops around to enter at the south pole of the field. As with all things in nature this path is path of least resistance. Each line of magnetic force is repelled by the adjacent lines of force while simultaneously being attracted by the opposing pole of the magnet. This is why we get the characteristic field shape of a bar magnet or a solenoid.

Mathematically the line of force that comes out of the center of the magnetic field extends to infinity before looping back to the other pole but as D_Hersey correctly pointed out we have some form of inverse square law to deal with with respect to the intensity of the field as we go out. This makes the extension of the strength field dependent on the length of the magnet or solenoid to some extent and also the power that we put into the generation of the field. If you are looking for some way to focus the power of your solenoid's magnetic field so that you can project the magnetic effect an extended distance with a limited power source you have a very difficult engineering problem. The nature of the magnetic field is not amenable to this type of manipulation. I do not think that the converter will be of much help. For any specific coil resistance increasing the voltage will increase the current and thus increase the strength of the field but it will also create a commensurate increase in current draw from your battery. What I mean is that there will be no magic free increase in field intensity without paying for it with additional power input.

John

Bravo John!

So often in physics, if we are dealing with a polynomial it is a second-order one.

I saw a product called a 'magnetic lens' once.  It was a radially symmetrical piece of ferrite that was fat on one and skinny on the other.  The intention IIRC, was to put the fat end near the sensed and the skinny end by a Hall-effect sensor.  But you are right, there isn't much going on in this dimension

Bravo John!

So often in physics, if we are dealing with a polynomial it is a second-order one.

I saw a product called a 'magnetic lens' once.  It was a radially symmetrical piece of ferrite that was fat on one and skinny on the other.  The intention IIRC, was to put the fat end near the sensed and the skinny end by a Hall-effect sensor.  But you are right, there isn't much going on in this dimension

Hi Don,

Yes the use of magnetic interactive materials can shape a field. Extending the core material of the solenoid can extend the field and there are diamagnetic materials that repel a magnetic field but in all of these cases the materials have to cover the distance. I get the impression that Les is hoping to project the magnetic field without material field shaping materials.

John

Wow, John you are all over this!  Sorry if I was being pedantic

That is what is so great about you being involved in a conversation. I always learn something as you push the limits and have such a great way of bringing in related ideas and topics.

John