Getting Started

Chapter 9 – Digital Meets Analog – ADC and DAC

ng is 0.0 volts.

rrrrm ed to put a

ltage on pin 2 of J407 on the Butterfly. But first we need solder some wires on a

tentiometer so we can vary a voltage. The JAMECO parts list has a 10 k Ohm

, we connect one side to +3v and the other to

t 1 of J407, the ADC connector, as shown

Figu ntiometer shaft we move a wiper connected to

center wire up or down. The full +3v is dropped across the potentiometer and

e center leg ‘sees’ a voltage proportional to the resistance above and below it.

The readi

U mmm... Oh yes, if we are going to measure voltage, we ne
vo
po
potentiometer listed. As in Figure 28
GND, hen we connect the middle to pin
in re 26. By turning the pote
the
th

+3v

GND

+2.1v

3 k Ohms above

7 k Ohms below

10 k Ohms

Potentiometer

Figure 28: Potentiometer Schematic