Self running coil?

[chadj]

Gotoluc,

Based on the information you gave me I was able to estimate the core permeability.

L=1050 (inductance in mH)
cw=3.5 (circumference of winding in cm)
N=800 (number of turns)
le=7.2 (my estimate of average circumference of toroid in cm)

Ae=((cw)^2)/(4*pi)=0.975 (area of toroid cross section in cm^2)
Al=(L*10^6)/(N^2)=1641 (nominal inductance L in mH)

finally...
permeability=(Al*le)/(4*pi*Ae)=967

The accuracy of this depends largely on the accuracy of the input values that are just approximations. Considering the permeability and appearance of your toroid I am guessing it is a NiZn ferrite.

I have wound quite a few cores in my time and know how hard it is. I cringe at the thought of winding 800 turns. There are machines that can quickly wind toroids and with this information you can place an order with a winding company (that's what I am doing).

Thanks,
Chad.

[gyulasun]

Hi Chad and Luc,

Recently I have come across a very good (and freeware) software on calculating toroidal coils inductances for any core. See here the mini Ring Core Calculator 1.2:

http://www.dl5swb.de/html/software_for_amateur_radio.htm

It can be used not only for known cores (where you know A_L or u permeability but for complitely unknown cores.  But this latter requires the unknown cores outside OD inside ID and height sizes and also a certain number of test turns what you can measure with your inductance meter.
Then the software uses these data in its Tools feature to calculate the relationship between A_L and u permeability and imports that for further calculations.  A very useful program.

So if Luc posts the OD, ID and height for the toroidal cores in question we can learn the core permeability pretty precisely. (MAybe Luc already posted the core sizes I have no time to wade through the thread.)

rgds,  Gyula

[gotoluc]

Gotoluc,

Based on the information you gave me I was able to estimate the core permeability.

L=1050 (inductance in mH)
cw=3.5 (circumference of winding in cm)
N=800 (number of turns)
le=7.2 (my estimate of average circumference of toroid in cm)

Ae=((cw)^2)/(4*pi)=0.975 (area of toroid cross section in cm^2)
Al=(L*10^6)/(N^2)=1641 (nominal inductance L in mH)

finally...
permeability=(Al*le)/(4*pi*Ae)=967

The accuracy of this depends largely on the accuracy of the input values that are just approximations. Considering the permeability and appearance of your toroid I am guessing it is a NiZn ferrite.

I have wound quite a few cores in my time and know how hard it is. I cringe at the thought of winding 800 turns. There are machines that can quickly wind toroids and with this information you can place an order with a winding company (that's what I am doing).

Thanks,
Chad.

Thanks Chad for calculating the core permeability.

They most likely have a permeability of 1000 seeing your result.

I picked up a digital caliper and here are the exact measurements of the core.  Opening diameter 0.814" or 20.67mm Outside diameter 1.358" or 34.5mm Maximum height point is 0.465" or 11.82mm Minimum height of rounded sides is 0.375" or 9.53mm Width is 0.27" or 6.87mm

Thanks for sharing

Luc

[gotoluc]

Hi Chad and Luc,

Recently I have come across a very good (and freeware) software on calculating toroidal coils inductances for any core. See here the mini Ring Core Calculator 1.2:

http://www.dl5swb.de/html/software_for_amateur_radio.htm

It can be used not only for known cores (where you know A_L or u permeability but for complitely unknown cores.  But this latter requires the unknown cores outside OD inside ID and height sizes and also a certain number of test turns what you can measure with your inductance meter.
Then the software uses these data in its Tools feature to calculate the relationship between A_L and u permeability and imports that for further calculations.  A very useful program.

So if Luc posts the OD, ID and height for the toroidal cores in question we can learn the core permeability pretty precisely. (MAybe Luc already posted the core sizes I have no time to wade through the thread.)

rgds,  Gyula

Thanks Gyula for the link to this toroid calculator software.

The core size is in the circuit diagram but I just picked up a digital caliper and here are the accurate measurements.

Opening diameter 0.814" or 20.67mm Outside diameter 1.358" or 34.5mm Maximum height point is 0.465" or 11.82mm Minimum height of rounded sides is 0.375" or 9.53mm Width is 0.27" or 6.87mm

Luc

[gyulasun]

Thank you Luc, and please one more data: a single layer of (any) number of turns gives ? uH or mH,  I know somewhere it could be found too...

Thanks, Gyula