Pull-up and Pull-down resistors

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A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow and adjust signal levels among other uses. Resistance is measured in Ohm with a sign of Ω.

A microcontroller (e.g. Arduino) utilizes I/O signals for communication with external hardware devices, where the most commonly known being GPIO. As a reminder, digital logic circuits have three logic states: high, low and floating (or high impedance). When there’s nothing connected to your GPIO pins, your program will read a floating impedance state, which we do not want. To achieve either high or low states, we’ll have to implement pull-up or pull-down resistors in our digital circuit.

Regulated power supply module based on AMS1117

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We often use the power supplies like batteries or direct AC/DC supply which are normally in higher ranges compared to the actual requirement for the circuit. In that cases we need this kind of voltage regulators which can regulate and vary the voltage levels for the circuit requirement.

The AMS1117 series of chips are linear voltage regulators with low voltage drop. The modules based on the AMS1117 chip provide constant 3.3V or 5V outputs from an unregulated DC input. It's very compact and can be included in your project schema or you can use it together with a breadboard for circuit testing.