The easiest way to do analog to digital conversion
is to use an IC such as the ADC0804 that does the work for you. The
analog voltage is applied to pin 6 and the result is available at pins
11 through 18. We will connect pin 1 and 2 (Chip Select and Read) to
ground so that the chip is always enabled. (If you wanted to use more
than one ADC you could use this pin to control which chip is currently
enabled).
Connect pin 7 (Vin - ) to ground. The ADC0804 includes an internal oscillator
which requires an external capacitor and resistor to operate. Connect
the 150 pF capacitor from pin 4 (CLOCK IN) to ground and the 10k ohm
resistor from pin 4 to pin 19 (CLOCK R).
Figure 2.5.1 Typical connection of free running mode
For example:
The input range of ADC is 0 - 5 volt
then we must setting Vref = 0.5 Vin maximum or = 2.5 volt
because this ADC0804 is 8 bit then V resolution = 5/255 = 0.02 volt this is mean that ADC will respon each 0,02V increasing
