Log/Lin Pots

[pwdrive]

If the wire was wound on a flat former and that assembly was shaped afterwards into a circular shape then maybe the wire might get stressed and strained and it's resistance might alter. Maybe it's wound like toroids are wound.

EDIT: Some are wound on ceramic formers, these cannot be flat then bent to shape, this would seem to suggest that whatever the former material is it is shaped first then wound afterwards.

Lawrence.

[Skywave]

Circular pots. with a non-linear law. Would it not be possible to exchange the positions of the wiper and the track, so that the track is the non-resistive conductor and the 'wiper' is the resistive element? That way, the resistive element could be shaped as a logarithmic spiral, producing a logarithmic law. That approach could be used to produce any law that was required.
However, something tells me that there is a snag in that idea, somewhere, since to my knowledge, that has never been done. And the companies like Bourns etc. must have huge R & D resources.

Al.

[pwdrive]

Having done a bit more digging my guess is that the former material starts off in tube form either full circular or circular with a slot and it's then cut into widths to provide a load of individual formers, from then on it's standard toroidal coil winding machine mechanics.
Any thoughts?

Lawrence.

[Retired]

Hi,

No problem at all coming up with new ideas Al especially if they work and work well.

Excellent suggestion Lawrence. Tufnol is still available in tube section so it would be very easy to obtain the correct diameter tube; remove a length to the width not required then slit into widths to suit the pots.

Because of the number of pot tracks involved it's highly likely the pot manufacturer would be in close contact with the Tufnol manufacturer having exact sized tubes made in quantity at hugely discounted prices; this also applies to resistance wire?

Because the track ends are open it wouldn't be difficult to design and make a dedicated winding machine for winding on the resistance wire. Winding by hand was easy for me whilst experimenting so a machine would considerably speed up winding.

Kind regards, Col.

[pwdrive]

Hi,

No problem at all coming up with new ideas Al especially if they work and work well.

Excellent suggestion Lawrence. Tufnol is still available in tube section so it would be very easy to obtain the correct diameter tube; remove a length to the width not required then slit into widths to suit the pots.

Because of the number of pot tracks involved it's highly likely the pot manufacturer would be in close contact with the Tufnol manufacturer having exact sized tubes made in quantity at hugely discounted prices; this also applies to resistance wire?

Because the track ends are open it wouldn't be difficult to design and make a dedicated winding machine for winding on the resistance wire. Winding by hand was easy for me whilst experimenting so a machine would considerably speed up winding.

Kind regards, Col.

The formers ends wouldn't have to be open for a toroid winder, the winding spool opens up for feeding through a closed circle ie: a ferrite toroid core or a closed former of some other material, once closed the spool is loaded up with the wire, the outer face of the toroid/former is rotated by a series of rubber rollers as the winding advances, these rollers also keep the toroid/former in place ie: the toroid/former turns to a constant center.

With a thin closed former for pots the same system would work if the pressure on the rollers is set low as not to deform the former, alternatively if the former had the cut out slot in it rollers could be also placed on the inside face of the former as well to stop any distortion of the former.
It is also possible that they are wound on a closed former and the slot is cut out after the winding has taken place.

There's a couple of Utube videos of commercial toroid winders showing them in action, search toroid winding or winder, I did post a link on this some time ago but not sure where it is now.

Lawrence.