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long as it can supply l ampere of current, or an external<br />
may be used to supply 12.6 volts ( ac) to the on-board power<br />
circuits. In either case, the breadboard pm•1er supply is<br />
from the computer power supply. A separate power supply is<br />
used because some computer systems cannot wpply sufficient<br />
for their ovm circuits and the added interface circuits that you<br />
wish to test. VVhenever an external power is used, you uu1xv•·"''"<br />
be sure that there is a good, low-resistance common ground<br />
tion between both power supplies. A power supply schematic<br />
shown in. Fig. 5-2.<br />
If the on-board power supply is to be used, the 12.6-V ac<br />
former is connected to pins l and 2 on plug number l (Pl); the<br />
i:iner diodes, Dl-D4, the filter capacitor, Cl, and the voltage<br />
VR, are aH installed. We suggest that a small heat sink be<br />
the +5-volt regulator. When the breadboard is used in<br />
manner, +5 volts are available at pin 5, and ground is available<br />
pin 6, on PL These connections may be used for external devices,<br />
required.<br />
If a separate +5-vol.t power supply is to be used, the power<br />
parts Dl-D4, Cl, and VR are not needed and should be =,ff.,=-<br />
ot installed. The +5-volt and ground connections are made at ,.,· '"'c<br />
5 and 6, respectively, at Pl.<br />
Since other voltages are often required, such as ±12 or ±15<br />
provision has been made at Pl to connect additional external nn,·wEor '''<br />
:rn
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