Circular ring on a PCB

Hi

I am relatively new to KiCad and PCB design in general and would like to replicate a similar ring on a PCB

image

I would also like to extend the FR4 to make a band along the diameter to support a smaller (2x2cm) PCB with a sensor in the middle. Can anyone help me?
Does anyone have ideas on contacts that I could use that are similar to the ones in the photo?

Thank you all in advance

KiCad still does not have proper tools for drawing arcs in tracks.
This has improved a bit i KiCad Nightly V7.99, in which net names can be assigned to graphical arcs on a copper layer, but in the current stable KiCad this does not work.

Working with the nightlies, has some advantages (newer features), but also has some drawbacks. The biggest drawback is that once a project is saved in the nightly, it can no longer be opened in the stable KiCad version.

As I already wrote, KiCad does not support a real / standalone arc in a track, but you can work around that by filleting tracks. This works as follows:

  1. Mark some position as the center of the arc, I put a mounting hole at (100, 100).
  2. Draw two track segments equidistant from that center. I choose a distance of 15mm.
  3. Select both track segments by dragging a box around the corner. Drag from right to left to also include the items crossing the box boundaries. Then right click and select Fillet Tracks from the popup menu. enter the radius for the fillet. (In this case 15mm).
  4. Remove the straight track segments, so only the arc is left.
  5. Use Copy [Ctrl +C] and Paste [Ctrl + V], and press R to rotate the new track segments before you give it itā€™s final position.

For the contacts, maybe those can be bought, but I suspect those are usually custom made. If it is for just a few, maybe you can use the brushes of a small DC motor, but that would be far too expensive for larger numbers.

Sorry, but this is just not true. Even in 7.0, the arcs in tracks are perfectly real.

Is there a feature request for this ā€œproperā€ tool you are missing? Please link it if so, and please make one if not.

It is one thing if KiCad doesnā€™t work the way you want it to, but please donā€™t exaggerate the situation and claim that arcs are not supported when thatā€™s not the case.

By the way, there is another way besides using the Fillet command to get the result you showed: you can also use the router in 90-degree arc mode. If the grid is set correctly, this makes drawing a complete circle take only a few clicks.

However, most likely the right solution for the original question is to make a custom footprint with custom-shape pads for each circle. That way, there is a defined location (anchor point) to make connections to the vias I see in the photo, and the shape of the circles is well-controlled and not subject to accidental modification in the board editor.

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Both the method I showed and your way with " 90-degree arc mode" draw the arcs as fillets, and I do not consider them standalone tracks. I do agree that ā€œnot supportedā€ may have been too strong words for the difference.

I am considering making a feature request for this, but I have to install the nightly first to experiment a bit with how that works before I make a feature request. Unfortunately Iā€™m having some troubles with the nightlies at the moment.

Designing a footprint for this is indeed probably a better solution. In the footprint editor you can directly add graphical arcs to a pad.

I donā€™t care what folks say - I do things my wayā€¦

We (I) donā€™t know enough about whatā€™s in the posted photo (looks like continuous/un-broken circular tracks that may have contactsā€¦? canā€™t sayā€¦ BUT,

Contacts like shown are generally referred to ā€˜Leaf Contactsā€™ (I know, I designed them for AMP, TE, JAE).

Regarding the Circular tracks:
If just wanting them without NETā€™s, draw circles on Cu layer.
If wanting them with NETā€™s, see video belowā€¦

(shows snippet of doing it then dragging into view one previously done - to save video time/file-sizeā€¦). DRC? I never bother and generally donā€™t careā€¦

Iā€™m always amused by Experts saying ā€œcanā€™t do this, canā€™t do thatā€¦ā€

I see (V7 stable) no problem with 360Ā° circle as in PCB editor there is separate tool for it. But I see problems when drawing not 360Ā° arcs when you want to have center when you want it and radius as you want it and you donā€™t know the exact angle at first but want to modify it later.
Feature request:

zip probably better shows the harder task to reach than graphic in that my request.

A ā€œfilletā€ is not an object in KiCad. ā€œFilletā€ is a command that creates true standalone arc tracks.

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ā€¦And, that is why I showed in Video you can set them to a NET.

Set one to a Net and all the connected otherā€™s get set to the same Netā€¦

Maybe something like this or something else from their range, you will have to investigate . . .

The search term you probably want is ā€œmulti-contact wiperā€
I canā€™t find someone with a quick search who makes these as standard catalog parts that you can order easily, so it might involve working with a vendor to find a part that would work for your application.

Standard spring contacts are typically not designed for maintaining good connection in the face of motion of the contact surfaces: they would more typically be seen in situations where you mate two parts together that donā€™t move relative to each other while a connection is needed (for example, a removable battery pack)

zooming in, I see there is a Connector Housing and some THTā€™s or Viaā€™s, otherā€¦ but, we have no ideaā€¦

I suggest OP look at his current part (assuming itā€™s not a photo grabbed off the net for a Curiosity-Can-I-Make-One because it looks coolā€¦

It may have a Part-Numberā€¦

No, itā€™s not a Wiper contact - wipers are used for Wiping as in, say, a Wiper in contact with a rotating Rotor/Armatureā€¦

If you missed my previous comment, I designed (and have patents on connectors) from years with AMP, TE, JAE including being Director of Engineeringā€¦ not boasting, just saying I may know something about this stuffā€¦

Call them what you want, off-the-shelf things like this are most often designed for particular products/customers and are (generally) not sold to those beyond those who paid for the design/tooling (until product is no longer in a contract arrangement).

But, you may find them at electronic sales companies that buy/sell salvageā€¦

The part in the bottom of the photo is a multi-contact wiper. OP hasnā€™t said what this is for, but it looks a lot like a rotating system to meā€¦

Hence, my comment - for a rotating systemā€¦

I CORRECT MYSELF - yes, you did say/interpret correctly that what is shown is a Wipperā€¦ I had in mind the Contact posted by Raptorā€¦

I apologizeā€¦ :rofl:

Yesā€¦ I donā€™t know why you said above that you were confident it was not a wiper, and now you are saying you commented that it was for a rotating system :slight_smile:

Perhaps: https://www.harwin.com/products/S7271-45R/

Long ago and far away, in the bad old days of Video Cassette Recorders, ā€œmode switchesā€ were often present.
Their reliability was right up there with perished rubber drive bands. :grimacing:

ksnip_20231207-093929

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goolgling for ā€œslip ring contactsā€ brings to some images from manufacturer of slip rings that seems to propose what you are looking for, not sure if they sell the contacts or just the complete systemā€¦

image

PS: i think searching for ā€œslip ring brushesā€ can lead you somewhere:

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