Inductor

[cdonke]

I just can't find an specific inductor...
It only says that it must have:
Diam: 5 mm
Wire: 0,5 mm
Turns: 8

What should be it's inductance??? How can I calculate it???

Can I replace it somehow?? With some resistor, another inductor, ow something??

Does the distance between turns affects the component???

Tks,
Christiano.

[quantum]

Cdonke,

1. The factors that determine the inductance is number of turns, area of the coil, length of the coil, and the core of the material used. Your description doesn't include the core material, so the measurements cannot be determined.
2. You can calculate the inductance in henrys (L), after Joseph Henry. The formula is L= N* x A x u/ l. L is the inductance, in henrys, N is number of turns ( the "*" is meant for the number of turns to be squared). Times the cross-sectional area, in square meters. Times permabilty of the core. Divided by the length of the core, in meters.
3. I guess you can replace it with another kind of inductor, with same measurement of henrys though, but not for a resistor.
4. Yes, the distances between each coil does matter.

[Kain]

Cdonke, I assume you are trying to build some radio transmitter. The formula that Quantum gives you is approximation by the way that sometimes works sometimes not (for me it did and didn't as well), and it is for single layer coil, meaning that you cannot do (you can but the error will be greater) calculation for multiple layer coils. I advise you to follow the instructions on the schematic you are trying to build. Inductance cannot be replaced by resistor in general, but it depends what is the role of this inductor in the circuit you are using. A coil can be used to filter certain frequencies, for example, thus it works as resistor in some circuits, but notice a regular resistor limits all current no matter of frequency; so you see it depends on the circuit you are using. The distance between the turns affects the inductance - higher distance results on lower inductance. If they say nothing about spacing between the turns, assume it's 0. What is the circuit that you are building though?

[cdonke]

I'm trying to build the damn TV Signal Amplifier but it came without some important information... Like the lenght of the Inductor or its inductance...

I am assuming that its lenght is 0.72 cm. ( Number I came through an insane proportion of sizes from an image of the circuit that I'm trying)
This way, using Quantum's equation: (8^2 * 0.05^2) / 0.0072, resulting ~22

I will assume too, that the distance among turns is 0.

[Kain]

Cdonke, if you know the purpose of this inductor in the circuit you will be able to calculate its inductance as well. It's probably a filter by the way. Actually I just checked - it's a filter yes. Notice that you have the same LC filter on the input and output. It is put there to cut frequencies in the specified region I guess. Just try your best to make the coils as similar as possible.

[MP]

Here are some tools that will help:

http://www.csgnetwork.com/spiralcoilinduccalc.html

http://www.lalena.com/audio/calculator/inductor/

http://emcsun.ece.umr.edu/new-induct/

You should be able to find the value of your inductor with one of the above.

MP

[steven]

:)