Hi Forum Members,
I am relatively new to the world of electronics and still trying to grasp some of the fundamentals. So this may be a very basic question. Please refer to both attached diagram and picture supplementing my narrative below.
I was playing around with my Arduino Uno, building a circuit to see how pullup resistors function. The experiment went as expected, with the open gate triggering a HIGH condition at digital input pin #7. I specifically used a very large resistance to see if it would register a voltage across, as part of the voltage divider circuit with the large pin internal resistance/impedence. For this reason the pullup resistor consisted of three 820kOhm resistors in series.
Things got interesting when I started measuring voltages. With the gate OPEN, the voltage across the three resistors measured around 0.22V, telling me that pin 7 saw a sufficiently high voltage to trigger the HIGH condition, which it did.
I then measured the voltage relative to ground for each of the three resistors (please see diagram). As expected V1 registered V1 = 5V. The voltage taken from inbetween R1 and R2 and GND registered at 2.74V. Similarly, V3 = 1.89V and Vx = 1.43V. How is this possible if the voltage at Pin 7 was sufficient to trigger a HIGH condition? I assume the voltage measured by Pin 7 is relative to the same GND I used in my measurements (please see photo).
I am obviously missing something elementary. Any advice/direction would be appreciated.