Microcomputer Circuits and Processes
Microcomputer Circuits and Processes
Microcomputer Circuits and Processes
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using the A-to-D converter. Since CONDAC only has one A-to-D<br />
input <strong>and</strong> two are needed, the input must be switched from one signal to<br />
the other. A mechanical switch could be used, but there are chips which<br />
can do this job very well (CD 4052 or MUX 08). These chips can switch<br />
very quickly, <strong>and</strong> can be driven by CONDAC's digital output port.<br />
(a)<br />
anemometer<br />
thermometer<br />
9 baro9_eter ---+<br />
l<br />
:to A-to-D converters<br />
to digital<br />
input port<br />
from digital<br />
port<br />
output<br />
siren<br />
(b)<br />
disk<br />
light source<br />
photodetector<br />
Side view of disk<br />
square wave to<br />
digital input<br />
port<br />
Plan view of disk<br />
Figure 4.40<br />
(a) A small weather station. Temperature <strong>and</strong> pressure measurements are made using<br />
A-to-D converters. The detailed drawing (b) shows how the speed of the rotating windspeed<br />
shaft is converted to a square wave using a light source <strong>and</strong> photodetector.<br />
This square wave is fed into a digital input of the microcomputer.<br />
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