Parametric pcb traces

Layout
1

Hi,

I am trying to lay out the ips2550 encoder in kicad. It is basically a resolver replacement that allows through shaft position sensing, quite useful…

https://www.renesas.com/en/document/dst/ips2550-datasheet?r=1469886

My issue is that it involves sinusoidally drawn traces, basically it’s loops of the form

R=A +Bsin(ntheta+D)

The traces could be any thickness, 0.2 or 0.25mm probably ideal.

Ideally i think it would be a footprint but I’ll take anything that gets the job done…

Any idea how to achieve this? Maybe I’m missing something obvious but I’m feeling a bit lost honestly.

2

In KiCad we call them tracks. But…do they need to be tracks or can they just be copper shapes?

I am thinking to use an Excel Chart to create a sinewave. Then that chart becomes an image in a format such as .png.

Can you put that .png onto a copper layer?

3

As long as I can attach a net to them and therefore wire them into the chip they can be tracks or polygons or whatever…

I can probably generate the shapes in Solidworks. Export as dxf or pdf or png or something like that. Was hoping there was a native kicad thing to do it because relying on Solidworks is a pain, as is generating png from an excel (with the added complication that it’s a fundamentally polar coordinate problem).

4

desmos-graph
desmos-graph800×800 94.1 KB

Its easy enough to get the image.

5

There was a python script flying around to generate the needed patterns for these sensors

But… If you can generate a plot and generate an SVG, you can import the SVG into Kicad and use it as copper

Matplotlib can export as svg

6

In my opinion, Solidworks is much more convenient in this regard

7

Sage Math might be able to do this according to a quick search. A ‘tad’ cheaper too. :wink:

8

For footprints take a look at GitHub - in3otd/spiki: A spiral inductor footprint generator for Kicad

9

There’s a function plotter in Inkscape (Extensions → Render → Function Plotter) with a polar mode that can be used for quick work (it’s not as accurate as a proper mathematical solvers, because the derivative is numerical for polar plots and there’s no adaptive sampling). But with enough sample points the error will be negligible:

image
image859×765 57.6 KB

10

Gnu Octave can plot functions like this for free

11

There are plenty of Posts on using DXF and Graphics so, I’ll stop at getting a Sine Curve, using FreeCAD (yes, there are many other ways to get the Curve).

Since you know SolidWorks, then you know 90% of FreeCAD’s ‘Part-Design’ Workbench. That said, video shows using the ‘Draft’ workbench and the Python Console in FreeCAD.

I simply dropped in the Code below and hit Enter-Key…

(FYI - I came to FreeCAD years ago after using SolidWorks, Pro-E and all the other’s… I use only FreeCAD now).

Oh, and there’s a nice Parametric Workbench with built-in functions that are editable… I use it to make Traces/Tracks in Kicad

import FreeCAD
import Draft
import math
pts = []
radius = 10
for ii in range(0,360):
pts.append(FreeCAD.Base.Vector(iimath.pi/180,math.sin(iimath.pi/180),0))

Draft.makeBSpline(pts)