Inductors

[tumler]

Hey,

I'm about to start building my first amplifier but I have been caught on what the inductor(choke) is?

I'm building the Jaycar Studio Series 350 amp and need a 6.8uH inductance.

Would somebody be able to give me a link or tell me how to make one.

And the only inductor / choke I can find in Jaycar with 6.8uH is a RF choke, I'm sure this won't work but could somebody please tell me the difference between a choke and inductor.

Thanks alot

 

[Leolabs]

Try to search on Wikipedia.

 

[rpapps]

Hi Tumler
The instructions for making it are in the Silicon Chip article, February 2004, page 23.
If you can't get hold of it, it's 23.5 turns of 1mm enamelled copper wire wound on a 13mm inside diameter plastic bobbin.
Wrap in insulating tape to hold winding in place.

Incidentally, depending on where you got the circuit from, there may be an error. Check the 470uF cap on the -70 rail adjacent to F2. The original schematic has this reversed and could be an explosion risk.

You should also check the notes & errata here:
http://www.siliconchip.com.au/cms/A_104440/article.html

Cheers
Rob

 

[tumler]

Thanks alot Rob
more than enough information to get me started

 

[rpapps]

Hi
You're welcome.
If you can't easily get the 13 mm bobbin, 1/2 inch or 12 mm dowel rod would probably be fine. Just make it 24 turns.
Cheers
Rob

 

[Nadis]

So came up with the same problem i dont realy understand 13mm inside diameter but how hight it must be how manny tusns per layer?

 

[AndrewT]

An AA battery makes a good bobbin for winding an amplifier output coil.

 

[Nadis]

its not that i dont have stuff to winde it on i need 3 dimensions to know how to do it: iner diameter of coil, turns per layer and how many turns.

 

[AndrewT]

Rp has already told you 23.5 or 24 T

Rp told you 13mm
I told you AA battery, approx 13.5mm

Choke = inductor

 

[Ian Finch]

Neither the inductor nor turns per layer is critical - it is only specified to a half-turn to give the lead spread to fit the PCB holes when the original coil is placed flat on the PCB as illustrated. If using 1mm enamelled wire, the number of turns will give about 10 turns per layer. However, there are dozens of formulae and free coil calculator programs on the web - why not use available information? Pronine Electronics Design - Multilayer Air Core Inductor Calculator

For interest, the original coil was specified for winding on obsolete P26/16 ferrite potcore bobbins, like this: http://electron-pv.com/PDFs/Ferrite/pot_p_26_16.pdf
Compare with kit amplifier pic here: Silicon Chip Online - Studio 350 Power Amplifier Module

 

[Nadis]

thank you Ian Finch.