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1 Lab Instructions

1.1 Layout

Choose a layout that places the components on the board in a logical arrangement and has the jumper pins on the opposite end from the bent pin header. A sample layout is provided for efficient design (see Figure 1). Follow this layout to be sure all your components will fit and the circuit will be easiest to use.
Figure 1: Sample Layout

  1. To create the 4x2 pin header, we need to combine two 4x1 headers broken off the large array in your kit, they simply snap apart between pins (try to use a needle-nose pliers to be sure it breaks in the right place). We will use a jumper block to make the necessary connections. The two 4x1 pin headers will need to be placed in parallel to each other so that the jumper block connects together one pin from each of the headers, as shown in Figure 2.
  2. Leave one blank row of holes between each component and its neighbor.
  3. Pay attention to the orientation mark on the socket which should indicate the correct orientation of the IC that plugs into it.
  4. Make sure that the power and ground pins of the IC's are not reversed as this will make them operate incorrectly or destroy them.
Figure 2: Pin Header for Jumper

1.2 Tack Soldering

All of the parts need to be tack soldered onto the proto board to keep them from shifting while wire wrapping, as shown in Figure 3. Here we are simply using solder as a means of mechanical attachment, not as an electrical connection.

Figure 3: Sample Tack Soldering

  1. When tack soldering, the goal is to temporarily attach the parts to the board so they can be wire wrapped. All parts should be tack soldered to the board but only the ones that easily come off must be tack soldered. To tack solder something just put enough solder to hold the part onto the board without impeding the wire wrap tool’s ability to wrap around the pin.
  2. Be careful, the soldering iron is very hot.
  3. After tack soldering the parts, install the pin ID labels, these help you easily identify the pin numbers on the bottom of the board.

1.3 Wire Routing

Figure 4 shows a wiring schematic. Look at your wiring schematic and consider where to run each wire. The wires need to be routed so that they are as short as possible yet as low density as possible (try to spread the wires out on the board rather than running them all through the same place. In general it is best to use the wide empty space between pin rows to run the wires, rather than running them between the pins where there is less space.

Figure 4: Sample Schematic

  1. Refer to the separate Wire Wrapping Tutorial for instructions on the process.
  2. Run all the wires for a single part or all the wires that connect together at the same time to reduce the chance for forgotten wires.
  3. Use a logical color scheme for the wires. For example, red for power and black for ground. If you use one color wire for all the power and ground lines, do not use that color for any other connection to prevent later confusion or cross-wiring. Organization is important to making the wires easy to trace.
  4. Six colors of wire are available: red, black, white, blue, yellow, green, as shown in Figure 5.
  5. Remember that when looking at the board from the bottom the pins are not in the same order that they are when looking from the top, this is why the ID labels are important.

1.4 Other Considerations

  1. The LED is provided to show the output of the slowest counter output. It needs to be hooked up in series with the resistor and the combination connected between the output and ground.
  2. Testing of the completed board is required! Using a logic analyzer or multimeter with frequency setting will display what speed each of the output pins is running at. You can also use the logic probe for slower clock speeds. Confirm that each of the jumper settings changes the speed of the outputs and that the outputs are operating at the expected speeds.
  3. After testing the board and confirming its accuracy, it is a good idea to trim the pins. The pins are long to facilitate wrapping wires around them. Once wrapping is complete, the pins can be trimmed to make the board take up less space. Use wire cutters to clip off the ends of the pins. Protect your eyes and clean up after yourself. Be sure you don't send pins flying around the room.
  4. Reminder: When your project is completed, the pins on front and back are exposed and live in the circuit. Use care in what you allow them to touch while the circuit is running, it would be easy to create a short circuit.

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Up: Lab 0: Wire Wrapping Previous: Lab 0: Wire Wrapping
Copyright © 2008, Electrical Engineering Department, New Mexico Tech
Last Modified 2008-09-03