Hi guys. I'm a noobie to this game and need some help for a simple project. I need to know how many turns of wire needed to make a 220 microhenry choke on a ferrite torroid core. According to the article that describes the specifics, the wire is to carry 6 amps peak for a few microseconds at a repetitive rate of 1000 Hz. I've gone through the inductor creation topic but can't make heads of the formulas posted. My torroid core is 10.0 mm inside diameter and 17.0 mm outside diamter. Its height is 8.0 mm. I certainly don't know its AL or permeability and I don't have any test instruments like the mentioned oscilloscope/signal generator, hence I can't verify the inductance of the resulting product. I just need a little information that will get me aproximately that much inductance. Thanks for any help.

 

I can't say I've ever had much to do with winding coils, BUT if you don't know the specs on the core you can't do the calculations. I can only suggest you try winding some turns round it and measure the inductance value you get? - assuming you have a method of measuring inductance?.

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What if we just assume that what I have is the ordinary dime a dozen kind you get off any Radio Shack outlet?

 

What values do they have?, and have you any reason to assume it's an identical core?.

Just blindly guessing isn't going to be any help!.

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You need to buy or borrow a multimeter that can measure inductance.

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Len

 

Does it need to be 220uH, or just a minimum of 220uH as a filter choke might require? Be a good idea to say what you want to do with this.

You mention a fairly substantial peak current. You should give some attention to the issue of saturation current in the design. If saturation current is exceeded the current rises very quickly and this can be bad for many applications.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

Not all Ferrites or Tottoids are made to handle Power. The Turns for a Specific Inductance is related to the AL Value.

The Physical Size is Somewhat related to Power, But it Varies considerably from one Core Material to the Next.

The Current and Frequency Capability are related to the Core Material.

Without knowing this info or having the Equipment to test he final choke, I anyones guess as to results.

I Wind Lots of chokes, coils. transformers and torroids and If you were to mail your core to me, I could tell you this info. Possibly even wind the coil for you.

Why not just Buy a 220uH Power type Choke?

Good Luck............Gary

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A 220uH inductor, 5.8 amps (close enough) costs $2.78 at Mouser. No minimum order, so do the easy thing. Part number 542-2316-h

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An iron powder toroid with a 0.5" ID is such that 100 turns will yeild from 22 microhenries to 450 microhenries.

A similar ferrite toroid is such that 1000 turns will yeild from 22 millihenries to 1170 millihenries.

With no more information than you've provided it would seem that there is a pretty wide range of possible outcomes.

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stevez

 

Thanks a lot guys. It's for a zapper for rechargeable battery rejuvenation. While it would be much easier to simply buy one, I'm hoping to gain some knowledge from the experience of making my own, plus the satisfaction of having done it myself.

 

Many of the people here are just trying to warn you of some possible sticking points or frustration points. If you proceed with the unknown core the odds do not seem to be in your favor that you'll come close to the value of inductor that you need - given the wide range of possible values. We don't know if the value of the inductor is at all critical. If the circuit doesn't work (which seems likely) then you might invest some time in troubleshooting and end up at a dead end. Sure you might learn something but there's enough risk in the DIY approach without adding an unknown component. I'd argue that there's enough learning and accomplishment potential with an inductor of known value.

Give some thought to the opportunities for error - given your skills and resources (tools, equipment, etc) and see where you come out.

Good luck and keep at it.

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stevez

 

Well I finally got myself an oscilloscope and signal generator. Using them and the formula for resonance, I found that I need 40 turns of wire to make 220 uH. My core is a pair of yellow torroids stacked together and taken from junk computer power supplies. I used 2 cores because this needs less turns than if I had used only one. Plus the bonus that the saturation point for these coils is much higher.

 

For your future reference, the original application of the cores (including which part of the supply it came from) and the core color are extremely useful bits of information.

 

You need to know the characteristics of the ferrite before you can get the required inductance.

Then why don't you post a link to it so we can help you out with the formulae you don't understand?

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