EECS - C96 ENGINEERING DESIGN & ENTREPRENEURSHIP
THE DESIGN EXERCISE

Our C96 computer has a licensed copy of PADS LOGIC software for schematic capture and PADS WORKS software for printed-circuit board layout. Although the schematic capture software is old, the printed-circuit board layout software is new and very advanced. There is more material to learn about circuit board design than we have time to cover in class. Therefore, you will want to work as a group to learn how to use these tools. In particular, the old parts library is badly out of date; so,you will probably want to learn to design your own parts files. This is especially true if you want to build a board for use in future laboratory courses - such as C96 taken as an independent elective.

The current PADS package costs about $2,200 and runs on WINDOWS-95 computers that have VGA or SVGA graphics capability. It will generate all of the files and documentation that are required to build a successful commercial product and, as a C96 student or alumnus, you are welcome to use it for that purpose. In addition to PADS, approximately twenty other companies sell comparable products. Some of these competitors make their schematic capture (but not board layout) programs available as freeware on the INTERNET - so check our C96 Home Page.

The following are basic steps required to manufacture a successful commercial product:

  1. Capture a schematic into a computer file. DO NOT BUILD WIRE- WRAP BOARD PROTOTYPES as they will not match performance of production products.
  2. Bring the schematic capture file into a simulator program - such as SUSIECAD- to test for timing or other performance characteristics.
  3. Bring the schematic capture file into the board layout program and then proceed with your parts placement, trace layout for each of the layers, legend layout and solder mask layout.
  4. Generate files for board outline, copper plating for each layer of board, legend mask, solder mask, drill pattern and bill-of-materials.
  5. Deliver the files to an assembly house of your choice which will arrange for manufacture of bare boards - the first few of which are delivered to you for test and evaluation.
  6. Arrange with your hardware vendors to deliver small quantities of parts to your assembly house to build test and evaluation units.
  7. Test and evaluate the first prototype boards. Make trace cuts, add jumpers and incorporate other changes as needed to achieve specifications. Repeat steps 1 - 6 as often as necessary until your board performs correctly. Archive each iteration of files so you can go back.
  8. When you product performs correctly, place your advertising, order parts and commit to assembly quantities.
  9. Many assembly houses will serve as order fulfillment centers - they will also package and drop ship your orders. If your assembly house does not offer this service, then arrange shipment to an appropriate fulfillment center.

You should note that your talent will permit you to launch a product with relatively little money.

Your PADS assignment comprises the following requirements:

  1. Select or design a schematic with 6-8 Integrated Circuits (ICs) - each of which has 16 or more pins - so that the total IC pin count is approximately 100 pins. Avoid trivial circuits. Look at the ARRL Radio Amateur's Handbook, parts catalogues, applications notes, equipment service manuals, magazines, textbooks, specification sheets, and INTERNET publications for candidate circuits. You may copy a schematic from any source other than a C96er or any of the PADS documentation. If you copy a schematic, you must identify the source.
  2. Write a short description (approximately 500 words) of how the circuit functions.
    A. Begin with a one paragraph abstract describing the attribute(s) of the circuit you consider to be most important.
    B. Describe how the circuit functions.
    C. Identify each component by a part number (i.e. R2 for a resistor) and describe the function of that component as well as its structural/functional relationship with at least one other component.
    D. End your description with a single-sentence description of that portion of the circuit which provides the most important attribute(s) you identified in your beginning abstract. The description must describe essential elements by generic name (i.e. resistor) or by function (i.e. means for converting electric energy into heat energy).
    You will find it easier to write your description if you start with the last section (the single-sentence description) and work backwards to the abstract.
  1. Capture your schematic with PADS LOGIC software. Keep a backup copy on your own 3½" disk in case something happens to your copy on the computer's hard drive.
  2. Convert your PADS LOGIC file into a PADS WORKS file and complete all necessary steps for generating files described in 3, above. Keep a backup copy on your own 3½" disk in case something happens to your copy on the computer's hard drive.
  3. Prepare a ten minute oral class presentation on the merits of your design and the problems you overcame.

As you complete each requirement, submit it as part of your WPR. You may submit your work on a 3-1/4" disk. Keep your backup disk.

This is a difficult assignment - so you want to start now and you will need to ask many questions. Your chances of success are materially enhanced if you work with other students. All work is due by the end of term - NO EXCEPTIONS and NO EXTENSIONS. To meet this deadline, establish a weekly schedule of milestones. If you plan carefully and execute your plan, then you will be successful.

Sheldon L. Epstein