Arc

Parent page: PCB Objects

Two placed Arcs (the one on the right is a Full Circle Arc).

Summary

An arc is a primitive design object. It is essentially a circular track segment that can be placed on any layer. Arcs can have a variety of uses in PCB layout. For example, they can be used when defining component outlines on the overlay layers, or on a mechanical layer to indicate the board outline, edges of cut outs, and so on. They can also be used to produce curved paths while interactively routing. Arcs can be open, or closed to create a circle (often referred to as a full circle arc).

Availability

Arcs are available for placement in both PCB and PCB Library Editors:

PCB Editor

  • Click Home | Place |  and select the required placement mode from the menu.
  • Click Home | Place |  to immediately place an arc as a full circle.

PCB Library Editor

  • Click Home | Place |  to place an arc in Edge mode.
  • Click Home | Place |  and select a different placement mode from the menu.

Placement

The way in which an arc is placed depends on the particular method of placement that you have chosen to invoke. Four different methods of arc placement are supported:

  • Place arc by center – this method enables you to place an arc object using the arc center as the starting point.
  • Place arc by edge – this method enables you to place an arc object using the edge of the arc as the starting point. The arc angle is fixed at 90°.
  • Place arc by edge (any angle) – this method enables you to place an arc object using the edge of the arc as the starting point. The angle of the arc can be any value.
  • Place full circle arc – this method enables you to place a 360° (full circle) arc.

Placing an Arc Starting at the Center

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the center point of the arc.
  2. Move the cursor to adjust the radius of the arc, then click or press Enter to set it.
  3. Move the cursor to adjust the start point for the arc, then click or press Enter to anchor it.
  4. Move the cursor to change the position of the arc's end point, then click or press Enter to anchor it and complete placement of the arc.
  5. Continue placing further arcs, or right-click or press Esc to exit placement mode.

Placing an Arc Starting at the Edge

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the start point for the arc.
  2. Move the cursor to change the position of the arc's end point, then click or press Enter to anchor it and complete placement of the arc.
  3. Continue placing further arcs, or right-click or press Esc to exit placement mode.

Placing an Arc Starting at the Edge (any angle)

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the start point for the arc.
  2. Move the cursor to adjust the radius of the arc, then click or press Enter to anchor the center point.
  3. Move the cursor to change the position of the arc's end point, then click or press Enter to anchor it and complete placement of the arc.
  4. Continue placing further arcs, or right-click or press Esc to exit placement mode.

Placing a Full Circle Arc

After launching the command, the cursor will change to a crosshair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the center point of the arc.
  2. Move the cursor to adjust the radius of the arc, then click or press Enter to set it and complete placement of the arc.
  3. Continue placing further arcs, or right-click or press Esc to exit placement mode.

Additional Placement Actions

Additional actions that can be performed during placement are:

  • For all methods (excluding full circle arcs), press the Spacebar before defining the arc's end point, to render the arc in the opposite direction.
  • Press the L key to flip the arc to the other side of the board – note that this is only possible prior to anchoring the arc's start/center point.
  • Press the + and - keys (on the numeric keypad) to cycle forward and backward through all visible layers in the design respectively – to change placement layer quickly.
  • Press the Tab key to access an associated properties dialog, from where properties for the arc can be changed on-the-fly.
While attributes can be modified during placement (Tab to bring up associated properties dialog), bear in mind that these will become the default settings for further placement.

Placing an Arc as a Keepout

An arc can be placed as a layer-specific keepout object or an all-layer keepout to act, for example, as a placement or routing barrier. Objects defined as keepouts are ignored during output generation, such as photo plotting and printing. A layer-specific keepout arc is simply an arc object with its Keepout property enabled, an all-layer keepout is an arc that has been placed on the Keepout layer.

  • To place a layer-specific keepout either place a standard arc on the required signal layer and then enable the Keepout checkbox to make it a layer-specific keepout, or use one of the predefined Arc keepout placement commands, available as follows:
    • PCB Editor - click Home | Place | .
    • PCB Library Editor - click Home | Place |  » Keepout.
  • To place an all-layer keepout make the Keepout layer the active layer, then place a standard arc from the Ribbon.

Graphical Editing

This method of editing allows you to select a placed arc object directly in the workspace and change its size, shape or location, graphically.

When an arc object is selected, the following editing handles are available:

Selected Arcs (Full Circle Arc on right).

  • Click and drag A to adjust the radius.
  • Click and drag B to adjust the end points (start and end angles).
  • Click anywhere on the arc – away from editing handles – and drag to reposition it. While dragging, the arc can be rotated or mirrored:
    • Press the Spacebar to rotate the arc anti-clockwise or Shift+Spacebar for clockwise rotation. Rotation is in accordance with the value for the Rotation Step, defined on the PCB Editor – General page of the Preferences dialog.
    • Press the X or Y keys to mirror the arc along the X-axis or Y-axis respectively.

An object that has its Locked property enabled cannot be selected or graphically edited. Double click on the locked object directly and disable the Locked property, to graphically edit the object.

Non-Graphical Editing

The following methods of non-graphical editing are available:

Editing via an Associated Properties Dialog

Dialog page: Arc

This method of editing uses the following dialog to modify the properties of an arc object.

The Arc dialog can be accessed during placement by pressing the Tab key.

After placement, the dialog can be accessed in one of the following ways:

  • Double-clicking on the placed arc object.
  • Placing the cursor over the arc object, right-clicking and choosing Properties from the context menu.

Quickly change the units of measurement currently used in the dialog between metric (mm) and imperial (mil) using the Ctrl+Q shortcut. This affects the dialog only and does not change the actual measurement unit employed for the board, as determined by the  and  buttons in the Home | Grids and Units area of the main menus.

Editing via an Inspector Panel

Panel pages: PCB Inspector, PCBLIB Inspector

An Inspector panel enables the designer to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering, the panel can be used to make changes to multiple objects of the same kind, from one convenient location.