pcb-rnd knowledge pool


Using and editing arcs on layouts in pcb-rnd

arc_edit by Erich Heinzle on 2018-01-17

Tags: howto, arc, edit, clearance, route, styles, circle, menufile

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Abstract: Show how arcs can be drawn, modified, and how various settings affect their use.

  How to create and modify arcs in pcb-rnd.

In contrast to some other EDA tools, pcb-rnd treats arcs as simple geometric features with no associated electrical "Net" that imposes restrictions on arc characteristics.

Furthermore, pcb-rnd supports arcs on copper and outline layers and within fonts, and can do DRC (design rule) checks which include copper arcs.

After lines , arcs are one of the simplest way to implement tracks on PCB layouts, as well as board outline geometry, artwork on the silk screen layer, or apertures in the solder mask layer.

The arc tool behaves much like a arc drawing tool in other two dimensional drawing software.

The arc tool can be selected from the toolbar:

The intended layer for the tracks needs to be selected too, which will typically be a copper, silk or outline layer

The line can be started with a click of the mouse or trackpad at the desired location:

the arc will then extend and resize as a quadrant segment to meet the pointer. Using the SHIFT key will flip the concavity of the arc:

Clicking once more lays down the positioned arc

At this stage, the last point remains an origin for further routing if required, that continues from that point

The continued trackwork can then be laid down with another click:

Once the arcs have been laid, the arc tool can be exited by using the ESCAPE key or clicking on the select tool:

By holding the mouse over an arc and using the key sequence e, g, s (written as {e g s} for short), the arc can be fattened:

Routing styles

In addition to using {e g s} to thicken individual arc segments, the "Route Styles" settings can be used to modify the thickness of lines and arcs currently being drawn with the line or arc tool.

pcb-rnd has four route style settings, any one of which can be selected for drawing and/or modified if required:

In this case, we make the normally "thin signal" style thicker to demonstrate

and we see the effect on an arc drawn with the now modified signal route style:

snapping and sizes

The cursor will snap to the end point of arcs automatically, allowing the user to continue laying further arcs or tracks easily, or modify the existing arc:

Clicking and dragging on the end of the arc with the select tool allows it to be moved:

In addition, clicking on the end of an arc and then using SHIFT allows the radius to be modified

With the cursor over an arc, {e g SHIFT-s} will make the arc thinner; the opposite effect of the {e g c} key on an arc


The clearance of an arc can be easily adjusted by using the {e g c} and {e g SHIFT-c} keys when the cursor is over the arc.

Here is the original clearance visible around an arc laid across a copper polygon:

The {e g c} key is used to increase clearance:

and {e g SHIFT-c} is used to reduce clearance:

Further {e g SHIFT-c} use ultimately extinguishes the clearance completely, electrically connecting the arc to the copper polygon: