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Subsections
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
|
- 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.
- Leave one blank row of holes between each component and its
neighbor.
- Pay attention to the orientation mark on the socket which should
indicate the correct orientation of the IC that plugs into it.
- 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
|
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
|
- 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.
- Be careful, the soldering iron is very hot.
- After tack soldering the parts, install the pin ID labels, these
help you easily identify the pin numbers on the bottom of
the board.
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
|
- Refer to the separate Wire Wrapping Tutorial
for instructions on the process.
- 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.
- 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.
- Six colors of wire are available: red, black, white, blue,
yellow, green, as shown in Figure 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.
- 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.
- 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.
- 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.
- 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.
Up: Lab 0: Wire Wrapping
Previous: Lab 0: Wire Wrapping
Copyright © 2008, Electrical Engineering Department, New Mexico Tech
Last Modified 2009-08-30