I have completed all sixteen circuits of the Sparkfun Inventor’s Kit as part of The STEMpunk Project[1], my year-long endeavor to become a ‘techie’.
After having learned a little bit about reading schematics I’m now trying to go back through some of the circuits to see if I can trace how power moves through them, and I’m getting stuck.
This is a picture of circuit #2, which contains a potentiometer that controls how quickly an LED blinks:
https://cdn.sparkfun.com/assets/learn_t … 2-v3_2.png
What exactly is happening here? I can see that power is coming from pin 13, flowing through the positive side of the LED and out its negative, and passing from there through a resistor on its way to ground.
How is the potentiometer connected to the LED? My hypothesis is that the Arduino circuitry just measures what happens to voltage when it flows from pin A0 to ground through the potentiometer. That means there is no direct connection between the two on the physical breadboard itself, right?
And if both the LED and the potentiometer are being powered by pins 13 and A0 respectively, why bother running wires from the redboard to 5v and ground at all?
[1] https://rulerstothesky.com/2016/03/10/t … ieve-them/
Hi tfowler,
The potentiometer is not connected to the LED at all. +5V and GND from the RedBoard are connected to the breadboard and the two fixed terminals of the potentiometer. The wiper terminal of the potentiometer is connected to A0 (an analog input) on the RedBoard. When wired this way, the wiper terminal will have a voltage on it that varies depending on how you turn potentiometer knob. A0 is an input into the RedBoard, not an output to the potentiometer.
The LED gets its power from PIN #13 and it ultimately flows back to the common GND connection on the breadboard (remember it’s tied to the RedBoard’s GND). PIN #13 is under the control of the RedBoard’s firmware so the LED can be turned on and off under software control.
Since the variable voltage of the potentiometer is connected to an analog-to-digital converter pin on the RedBoard, its microcontroller can convert the voltage into a digital value which can be used to make decisions in the firmware. In the case of the program you are running, as the voltage on pin A0 changes under your control with the potentiometer, the firmware adjusts the blinking rate of PIN #13 which drives the LED.
I hope that helps a little bit!
-Bill
It helps a lot, thank you!
