How to Design Your Own Breakout Cable

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This is a commercially made breakout cable.

Breakout cables and boards are useful troubleshooting tools. With them, a technician can move a circuit board or assembly out of the tight confines of a computer or other electronic device, gaining access to components and test points. There are two ways to construct a breakout cable. One is to run discrete wires between two connectors, forming a flexible cable. The other is constructed with two connectors fastened on opposite ends of a circuit board, with wires or plated runs between the connectors.

Things You'll Need

  • Jack
  • Plug
  • Stranded wire
  • Masking tape
  • Wire stripper
  • Pin insertion tool
  • Fiberglass circuit board
  • Soldering iron
  • Solder
  • Crimping tool
  • Cable ties
  • RTV
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Instructions

  1. Flexible Breakout Cable

    • 1

      Select an appropriate jack and plug for a flexible breakout cable. A circular Cannon plug, for instance, mates with a similar jack. Some older units use soldered pins, but modern units are crimped.

    • 2

      Cut the wire to length and mark each wire with a masking tape label for its position in the connector. Most Cannon plugs have pins labeled A through Z, then AA, BB, and on.

    • 3

      Strip the wire ends and crimp the pins. Push each pin into the connector with the insertion tool until it clicks. Use the labels to ensure that the pins are inserted in the correct positions in the other connector.

    • 4

      Wrap the wires into a convenient bundle with cable ties.

    Breakout Boards

    • 5

      Select appropriate edge connectors for a rigid breakout board. These are jacks and plugs that attach to the edge of a printed circuit board, and are used to connect boards to the back plane in a computer. They normally have through-mount pins or surface mount connections. Through-mounts will require a series of precisely drilled holes in the circuit board.

    • 6

      Fasten the connectors to the circuit board with screws and nuts. Check that there is sufficient clearance so it will not contact adjacent components.

    • 7

      Cut the wire to length, strip the ends, and form small loops to fit over the pin connections. Solder each wire in turn, following the pin numbers on the connectors. When finished, the wires should be parallel and lying flat on the circuit board. Tack them in place with RTV.

Tips & Warnings

  • Be aware that breakout cables and boards can introduce problems in troubleshooting. Long runs of parallel conductors exhibit capacitive effects, and signals can be coupled between them as a result. Circuits may be erratic or completely inoperative, and to make the situation more puzzling, identical boards may operate differently.

  • Exercise care when using breakout cables to connect high voltage to a test unit. A careless moment of inattention can result in a painful electric shock.

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References

  • Photo Credit Hemera Technologies/PhotoObjects.net/Getty Images

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