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how to route the cables also becomes easier, e.g. through an opening in the housing (or separate 3D model). The possibilities of 3D integration depend to a large extent Fig. 3: A little Samtec connector used to program a dsPIC33 microcontroller. on the quality and detail of the model. Using detailed contextual components Too often the components in a schematic are reduced to their strict detail, regardless of their use and function in the target application. As an example, look at the simple Samtec connector shown on figure 3. It is used to program a dsPIC33 microcontroller designed to communicate via a serial interface with a variety of developed modules (currently Bluetooth or FTDI RS-USB). On several occasions, this connector was placed without much thought in various board developments with the result that too often its orientation and / or placement no longer allowed the placement of the various modules. In figure 4, the red circle highlights the evident collision of the Bluetooth module with the housing (4a). This can easily be avoided by rotating the connector by 180 degrees or by increasing the distance to the housing (4b). If this problem is detected only after the PCB is mounted, a new iteration becomes necessary. To avoid such costly mistakes, it is advisable to use “detailed” components. These include not only the basic connector but also the specific plug-in modules and any other available modules, so that the developer is free to select which one to use for a specific board. A practical example In the following example, the same electronic board was to be used in two different parts of the same robot. To visualize this, it was enough to overlay the 3D models of the two robot parts, as shown in figures 5a, 5b and 5c. Figure 5a shows the complete robot while figures 5b and 5c show the different parts with two and three motors, respectively The robot housing is conductive and the PCB is fixed to it. Under those circumstances it was necessary to ensure that Fig. 5: (top left) the complete robot, (top right) a two-motor part, (bottom left) a threemotor part. none of the signal-carrying traces short-circuits. With a 3D view of the robot it was easy to determine the outline of the structures involved directly from within Altium, without the need to import a DXF file obtained from the M-CAD. It was enough then to define these areas as a Polygon Net GND. When taking the full mechanical context into account, the positioning of components on the board also becomes easier. Checks on the basis of 3D positioning rules for components Fig. 4: (left) The red circle highlights a collision between the Bluetooth module and the housing. (right) This can be avoided by rotating the connector by 180º or by increasing the distance to the housing. www.electronics-eetimes.com Electronic Engineering Times Europe April 2013 41


EETE APRIL 2013
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