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BREADBOARDING

by Stuart Ball

Start ý Grounding ý Placing Copper Strips ý Power Wiring and Supply Bypassing ý Lead Wiring ý Test Points ý Surface-Mount Parts ý Other Tips ý Putting It All Together ý Other Techniques ý Sources and PDF

POWER WIRING AND SUPPLY BYPASSING

In most digital designs, there are one or two digital supplies that need to be low-impedance. Usually, the power leads can be wired between the ICs using 26- or 28-gauge insulated wire. Bypass capacitors are connected between the supply leads and ground strips. Typical bypass capacitor values for digital/microprocessor circuits are 0.001 to 0.1 ýF. I usually use red wire for the logic power and yellow or orange wire for other supplies. This makes it easy to trace the wiring later.

For low-impedance power distribution, copper strips can be run on the top of the board, between the IC leads and directly over the copper ground strips. This provides a quality power connection, but it is more difficult to wire and you have to be sure you donýt short the upper and lower ground strips simultaneously.

In some cases, you want to locate a bypass capacitor close to the IC power lead, with no intervening wire. An example of this would be a processor or other component running at a high clock rate or generating fast (read, high switching noise) edges.

Figure 2 shows a way to handle these cases. In this example, a surface-mount capacitor is soldered directly to the IC lead and copper ground strip. You will typically use a 0805- or 1206-size surface-mount capacitor. Be careful not to apply so much soldering heat that the end caps detach from the capacitor.

Figure 2ýHere, a surface-mount capacitor is used to get bypassing close to an IC power lead. 1206-size capacitors are easiest to work with.

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