Let's Design and Build a (mostly) Digital Theremin!

20mH Solenoid

I 3D printed a clear PETG coil form, diameter 88mm and 140mm long, with 2 separately printed rib stiffeners added to the inside:

The print Z-stepping was set to 0.18mm, which is the OD of 34AWG single coat magnet wire.  Even with these as a guide, winding it was something of a bear.  The final inductance was somewhat off of that predicted by my coil program at 19.3mH.  DCR was 148 ohms.  Aspect ratio is 1.5.

On the test jig resonance was 1.66Vpp @ 265kHz, which means a Q of around 155.  Not super hot as the kit inductor Q's are around 170, but not super bad either.

Also messed with a bit of ferrite in a smaller 1mH solenoid:

Resonance before and after inserting the ferrite was 1.1723kHz => 765.2kHz, or a 2.35 magnification of inductance.  Q before and after was 131 => 114.  Again not the best but not crazy bad.  

I need stick both of these in the freezer to see what's going on with their tempco's.  My new LCR meter has more resolution than my old LC meter, and I guess I trust it more to be stable over the warm-up period.

Yo, fam, them homemade coils you got lookin’ like our chicks from the model spot, yo! They rockin’ that 90-60-90 vibe too, huh!

"Yo, fam, them homemade coils you got lookin’ like our chicks from the model spot, yo!"  - ILYA

Thanks homey, they do look pretty.  My favorite is TechFixx green wire on PVC.  The Remington wire I'm forced to buy (TechFixx only offers double coat now) has little kinks through the entire roll, and gets worse near the end.  I imagine this contributes to the winding difficulties.

"They rockin’ that 90-60-90 vibe too, huh!"

It took me a bit to figure out this was 36-24-36 in metric! :-)