How to make your own pot core

		Quote:			Posted by xavier
	Making your own pot core is possible here is how I made this one to test my theory first of all you need some ferrite that you crush till you have a fine powder then you make a mould I made this one out of paper and cardboard as it was only a test you should use moulding silicone as for the master you can make it out of what ever you like the best way would be to make it on a lath once you have the mould take ordinary resin (fibber glass resin)and mix it with your crushed ferrite remember that your mould must be longer than the ferrite pot that you want to make here is why place your mould on a strong magnet now pour in the mixture do not make it to thick the magnet will attract the ferrite to the bottom of the mould leaving the resin at the top you will later remove that section which is just resin place you mould in a plastic bag then in the fringe that will prevent the curing process of the resin with the catalyst more or less one hour later remove it from the fringe and place it in the sun it will harden very quickly how ever only use one to two drops of catalyst depending on ambient temperature. Ones hard remove from the mould if you have made a paper mould place it in warm water for an hour or so to soften the paper then scrape it out it will take you a while but it works remember to use floor or shoo polish so that the paper dose not stick to the wall of the pot. All you have to do now is make a cover for your pot core. Disadvantages Your pot core will not have the same properties as the ones you buy. It can get messy Have fun Xavier

So what is a pot core? The term escapes me.

How about using magnetite with the epoxy? It is very similar to the ferrite.

Magnetite just needs to be screened, not crushed (usually.) I once considered making a huge transformer core, by this method, with magnetite.

goldigger

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		Quote:			Posted by xavier
	Hi Goldigger   Sorry I should have said potcore normally a two part assembly that houses the coil with a central hole used for bolting down on a PCB.

OK, I have toroids.... no need for such a device, as toroids are self shielding. I have some small adjustable potcores that came out of an old telephone... I hate to rewind them, they are beautiful! The toroids, if I need a particular inductance, I divide by 1560 and take the  square root and then X100, this is turns required. Example 3300 uHy:

  SQRT of (3300 / 1560) = (1.45 X100) or 145 turns   These are 2 inch/50cm ferrite toroids.

To reverse this    sq(145t/100) X 1560 = 3279.9 uHy..... 146 t = 3325.3 uHy

253 t for 10,000 uHy! (A pain to wind.)

Different core material needs different no. of turns... you can find the magic number by winding 10 turns, measure the inductance, then multiply this by 10 and you have the core value for calculating any "turn:inductance" ratio.

I sure miss superscript.

goldigger


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		Quote:			Posted by xavier
	Well there we go again I have to wait till I have the means to measure inductance

Somebody here on this forum posted an adapter for a Digital Voltmeter that allowed it to read inductance. DIY, which is nice.

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		Quote:			Posted by xavier
	Hi goldDigger1950 Yes I have a number of those that I downloaded from the net but then you know how it goes you start to wonder well can?t I do this and can?t I do that. So I decided to do a proper job of it once and for all and build a proper LC meter. I will be able to use it for a long time and it should have 0.1% accuracy (or so I?m told) so should I need it I got it. Now you will probably say that to make metal detector coils I don?t need that kind of accuracy but at the same time I will know that I have done my very best on that coil and let me tell you that I?m kind of getting tired of winding coils that just don?t do what they should.  Like I said to Goldigger these coils are jumble wound now if they were flat coils it would be ok the thing is winding flat coils with thick wire is no problem but thin wire now that becomes one heck of a job. Xeronium has sent me a PIC programmer and that will help a lot I should be geting it any day now so now  I?m refining my search on the net to see what will be my best bet. I will keep you all posted of my progress. Best Regards Xavier                 PS. what free (if any) program should I download to write code and what tutorial should I get?

I do not wish to be a wet blanket, but I found out a shortcoming of PIC LC bridges... they are not bridges.

The PIC, which has an internal inductance and capacitance measures frequency first with out the added unknown component, then you add the component, and from the new frequency, it will calculate the value of the component. That is fine and OK, but it will never give true inductance, even though it is inductance with which you can live.

The problem: it NEVER takes into account 'distributed capacitance' of coils. Fortunately, distributed capacitance is not large enough to matter much, and distributed capacitance is not real capacitance, but functions as if it were, like an op amp "capacitor" circuit. 

Scramble winding probably reduces distributed capacitance, so do not be a perfectionist. 

I have had a PIC freq counter/LC bridge, which I bought as a kit from  EPE Mag kits, about  3 years ago. Maybe I should put it together, do you think? 

I still will build a real LCR bridge so I can measure this mostly useless distributed capacitance. 

I have also come up with an idea for a 'retro' frequency meter... not as simple as a PIC, but no programming, either.

6 months ago, I was offered a programmer and hounded until I said I would take it.... maybe I will get it by next May, Oz autumn. 

Programs for programming depend on the processor, some programs are able to do several, unrelated , processors, like 8051, 8951, PICs and AVRs. Try the free programs before sinking money into something that may not be appropriate.

Best way is Google search, download and play with them. I have several Microchip CDs and lots of OLD microchip programs like for PIC16C54, which is the heart of the BS1. Also, several Smart cards, available from JCAR, Aus, which have 16C54's or 16C/F84s. Put a card socket in your circuit and if you do not like the 16C54 program, get a smart card with 16F84 and use one of several programs out there. When you find a better program, program a new card!

goldigger

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		Quote:			Posted by xavier
	Put that kit together perhaps it will give you another brain wave

Could be.... It is supposed to be an LC meter that can also be used for a frequency counter.... It would solve some immediate problems. 

When I got the kit, I was suffering a B12 shortage, (which affects thinking, as well,) which I finally figured out, and was not able to hold on to a soldering iron, at the time. I prefer a soldering gun and mine is hefty. To top it off, I have a disabled right hand (car accident in 1975) and never learned to solder left handed, I AM ambidextrous, but even so, the hand has to be trained! Yes, it is just being stupid! I need to rig up a bungee cord to take the weight then it would be easy. I just have to raid my library for the issue of EPE that has the ARTICLE! 

How I figured out the B12 was: it happened to my Dad, when he was still living, and I got him to a doctor who informed me of the problem. Then a couple years ago, it started happening to me, and I do not know why, unless it is a side effect of type 2 diabetes. My Dad had Crohn's disease, which is a  auto-immune disease of the large intestine, but I do not have that. 

Maybe I can go back to soldering, HAH! I have been doing much more walking, enabled by the B12, I am sure. In severe B12 deficiency, one cannot absorb it at all and one has to have injections! 

goldigger

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