oscillator was located at the other end of the breadboard.
Figure 12 is the LCD with the external ADC.
If you connect the analog input circuit that was shown
earlier to the CA3306, the position control will not work
very well. The reason is that the CA3306 has low input
impedance. To compensate for that, we could add a
better analog input section. An LF353 or TL082 dual op-amp can provide gain up to about 4 MC and over one
million ohms of input impedance, as well as fixing the
position control issue. The drawback is that it requires a
negative nine to
12 volt power
supply. Two nine
volt batteries will
work. If you are
form viewer, you
may already have
running on a nine
volt battery, so
adding a second
one might not be as big of a problem. Figure 13 is a
simple analog input schematic diagram.
Next, the switches are connected from D12 and D13
to ground. They are scan frequency "up" and "down"
buttons. Then, the software can select between the
verbose method and the loop method for collecting the
data. Once using the loop method, a delayMicroseconds
(dtime); command can be added. The delay value can
then rotate between 1, 5, 10, 50, 100, 500, 1,000, and
5,000 at the push of a button. The complete code for the
46 March 2014
FIGURE 13. FIGURE 12.