1
\$\begingroup\$

I want to build this Arduino DDS waveform generator. A Chebyshef lowpass filter with a cutoff at 12 KHz is required to filter out the 32KHz sampling noise.

Chebyshef lowpass filter

The inductors are 4.7mH. Now in the photo, one can see, what I assume are Magnetic Core 4.7MH Radial inductors.

Photo of Chebyshef lowpass filter

I would like to know if I can use Axial inductors instead?

Axial inductor

Will the performance of the Chebyshef filter be the same or degraded?

I have no implementation, or design, specific reason for doing this, apart from cost. This question is similar to Axial inductor vs winding inductor, but the application (frequency range) is different, Audio (KHz) rather than FM (MHz), so I was not sure if that would affect the answer.

\$\endgroup\$
6
  • 2
    \$\begingroup\$ It doesn't look like a high-power or high-frequency application, so they will probably be ok if you can find one with the right value (which may be difficult for such a large inductance). \$\endgroup\$
    – Tom Carpenter
    Commented Aug 4, 2015 at 23:17
  • 1
    \$\begingroup\$ Magnetic core increases the amount of energy storage (large magnetic flywheel) before saturation, as a filter inductor it should do fine, but test and see really. \$\endgroup\$
    – crasic
    Commented Aug 4, 2015 at 23:28
  • 1
    \$\begingroup\$ Check the DC resistance is reasonably similar, and the rated peak current is high enough for the signal levels in your filter - with those points they'll probably be OK. \$\endgroup\$
    – user16324
    Commented Aug 4, 2015 at 23:46
  • \$\begingroup\$ @TomCarpenter - the set of Axial inductors that I linked to on eBay appear to have inductances ranging from 0.22uH to 4.7mH. \$\endgroup\$
    – Greenonline
    Commented Aug 6, 2015 at 20:41
  • \$\begingroup\$ It would never come to my mind to call PWM signal generation "DDS". \$\endgroup\$
    – Curd
    Commented Aug 6, 2015 at 21:19

1 Answer 1

Reset to default
3
\$\begingroup\$

The proposed ones will have a magnetic core only a different shape from the originals - there is no way that they can get 4.7mH without one. The original inductors are wound on what are called Drum cores. Your proposed one probably just has a cylindrical core. Since the magnetic field is not as well contained it will probably need more turns of finer wire which will increase its resistance and make it more lossy.

If the resistance of the proposed inductor is significantly different from the original the characteristics of the filter will be different.

Try simulating it in LTspice to compare the effect of any resistance change between the original and your proposed inductor.

I would expect it to perform adequately with the proposed parts.

\$\endgroup\$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.