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Circuit Development Path

 

Block Diagram  The development of a new circuit begins with the drawing of a block diagram, often first on the marker board, and then with CAD tools. The block diagram provides an opportunity for everyone to assure the same understanding without needing to all understand the circuit to the component level.

Click on the image for a larger view.

 

Schematic Diagram  Working from the block diagram, the schematic diagram of the actual circuit is designed and checked using CAD software.

 

PC Board Layout  The CAD software also couples the printed circuit board layout to the CAD file, assuring that each part and each connection in the schematic diagram is found on the board. The components must be moved around to optimal positions and the conductors must be routed. Most IDL boards are hand routed to minimize noise, optimize construction, and maintain correct impedances. Checks of clearances and other design rules are made by the software, and the layout is visually inspected and reviewed by another staff member.

 

Board Manufacture  The CAD software can generate "Gerber" files that describe the board completely, each of the layers of the board (typically 2-5), all dimensions, all drill sizes, and every routing coordinate. The Gerber files are emailed to one of several board manufacturers that specialize in prototypes. If we make sure that we conform to their automated production system, in 2-3 days, the boards are received.

 

Board Population  The board is usually populated by hand at KU. A great deal of skill is required to solder some chips to the board. If there are multiple copies of the board, it maybe cost-effective to send them to a specialized board-assembly house. Certain components (e.g., ball-grid packages) must be sent out for soldering to the board; they are X-rayed for quality before being returned.

 

Firmware and software  Firmware is frequently required for the microcontroller, graphical PC software for the user interface (the GUI).

An Integrated Development Environment (IDE) facilitates the firmware process.  The code is usually written in C, loaded into the microcontroller, and tested from the same software.  In this process, initial testing of the board occurs.

The GUI can be written in a variety of IDEs.  Often someone in the partner lab will handle this, in partnership with the IDL.

 

Mounting the board  After the board is completed and tested, it is mounted as necessary.  A plastic box might be optimum; a metal box or an rf-shielded box are sometimes needed.  Some boards become daughter boards on other boards.  If a specialized box is needed, we will draw the box with CAD software and have it built in the machine shop.  Mounts or openings for all connectors and switches are a part of this step.  The labels are usually created one at a time, but in other case, a full-panel, durable label can be designed.


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