- PCBNEW: Placement of the modules
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7 - Placement
of the modules
7.1 - Assisting
the Placement
- Whilst moving modules the module ratsnest (the net connections)
can be displayed to assist the placement. To enable this the icon
of the left toolbar must be activated.
7.2 - Manual
placement
- Select the module with the right mouse button then chose the
Move command from the menu. Move
the module to the required position and place it with the left mouse
button. If required the selected module can also be rotated,
inverted or edited. Select Cancel from the menu (or press the Esc
key) to abort.

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Here you can see the display of the module ratsnest during a move.
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The circuit once all the modules are placed may be as shown:

7.3 - General
Reorientation of the modules
- Initially all modules inherit the same orientation that they had
in the library (normally 0).
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If an alternative orientation is required for an individual module,
or all modules (for example all vertical) use the menu option
AutoPlace/Orient All Modules. This orientation can be
selective (for example to relate only to the modules whose reference
starts with “IC”. (Translators Note: This does
not seem to be working.)
7.4 - Automatic
Module Distribution
- Note:
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Generally modules can only be moved if they have not been “Fixed”.
This attribute can be turned on and off from the pop-up window
(click right mouse button over module) whilst in Module Mode, or
through the Edit Module Menu.
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As stated in the last chapter, new modules loaded during the reading
of the netlist appear piled up at a single location on the board.
PCBNEW allows an automatic distribution of the modules to make
manual selection and placement easier.
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Select the option “Module Mode” (Icon
on the upper toolbar).
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The PopUp window activated by the
right mouse button becomes:
If there is a module under the
cursor:

If there is nothing under the
cursor:

- In both cases the following
commands are available:
7.5 - Automatic
placement of the modules
7.5.1 - Characteristics of
the automatic placer
- The automatic module of placement allows the placement of the
modules onto the 2 faces of the circuit board (however switching a
module onto the copper layer is not automatic).
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It also seeks the best orientation (0, 90, - 90, 180 degrees) of the
module.
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The placement is made according to an optimization algorithm, which
seeks to minimize the length of the ratsnest, and which seeks to
create space between the larger modules with with many pads. The
order of placement is optimized to initially place these larger
modules with many pads.
7.5.2 - Preparation
- PCBNEW can thus place the modules automatically, however it is
necessary to guide this placement, because no software can guess
what the user wants to achieve.
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Before an automatic placement is carried out one must:
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- During automatic placement, if required, PCBNEW can optimize the
orientation of the modules. However rotation will only be attempted
if this has been authorized for the module (see Edit Module
Options).
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Usually resistances and non-polarized capacitors are authorized for
180 degrees rotation. Some modules (small transistors for example)
can be authorized for +/- 90 and 180 degrees rotation.
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For each module one slider authorizes 90 degree Rot(ation) and a
second slider authorizes 180 degree Rot(ation). A setting of 0
prevents rotation, a setting of 10 authorizes it, and an
intermediate value indicates a preference for/against rotation.
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The rotation authorization can be done by editing the module once it
is placed on the board. However it is preferable to set the required
options to the module in the library as these settings will then be
inherited each time the module is used..
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7.5.3 - Interactive
Autoplacement
- It may be necessary during automatic placement to stop (press
Esc key) and manually re-position a module. Using the command
Autoplace Next Module will restart the autoplacement from the
point at which it was stopped.
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The command Autoplace new modules allows
the automatic placement of the modules which have not been placed
already within the PCB outline. It will not move those within the
PCB outline even if they are not 'fixed'.
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The command Autoplace Module makes it possible to re-place
the module pointed to by the mouse, even if its 'fixed' attribute is
active.
7.5.4 - Note
- PCBNEW automatically determines the possible zone of placement
of the modules by respecting the shape of the board outline, which
is not necessarily rectangular (It can be round, or have cutouts…).
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If the board is not rectangular, the outline must be closed, so that
PCBNEW can determine what is inside and what is outside the outline.
In the same way, if there are internal cutouts, their outline will
have to be closed.
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PCBNEW calculates the possible zone of placement of the modules
using the outline of the board, then passes each module in turn over
this area in order to determine the optimum position at which to
place it.
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