A long time ago, I made a video suggesting math was unnecessary to determine proper pull-up resistor values. Like most generalized statements, that suggestion is not always true. For example, in data buses like I2C, speeds like 400 kHz and 1 MHz are common. At those speeds, the pull-up resistor and the bus capacitance form an RC filter that fundamentally limits the data transmission speed. Or. It limits the range of pull-up resistor values. In this Workbench Wednesdays video, I show how to estimate I2C bus capacitance, measure that capacitance, and pick pull-up resistor values.
When hooking up switches or buttons to an Arduino I/O pin, sometimes the results might appear completely random. Sometimes it will appear as though there is a delay from when the button is pressed until the state of the pin actually changes. Other times the pin’s value will seem to randomly fluctuate from HIGH to LOW. Even more maddening might be as your finger gets closer to the switch, the pin’s state changes! The fix to these problems is simple: use the Arduino Internal Pull-up Resistor. Here’s how they can fix this problem and how you can use them with an Arduino board.
