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Why do you need pull up resistor?
In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors , which physically interrupt the connection of subsequent components to ground or to VCC.
What is a weak pull up resistor?
A low resistor value is called a strong pull-up (more current flows), a high resistor value is called a weak pull-up (less current flows). The value of the pull-up resistor needs to be chosen to satisfy two conditions: When the button is pressed, the input pin is pulled low.
Does an output require a pull down resistor?
Another application is the I2C protocol bus, where pull-up resistors are used to enable a single pin to act as an input or an output. When not connected to a bus, the pin floats in a high-impedance state. Pull-down resistors are also used on outputs to provide a known output impedance. Power resistor.
What is the purpose of pullup and pulldown resistors?
A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH . A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW .
Is a resistor an input?
A voltage-controlled resistor (VCR) is a three-terminal active device with one input port and two output ports . The input-port voltage controls the value of the resistor between the output ports.
What is an internal pull up resistor?
Pull-up resistors may be discrete devices mounted on the same circuit board as the logic devices . Many microcontrollers intended for embedded control applications have internal, programmable pull-up resistors for logic inputs so that minimal external components are needed. Sep 16 2019
What is pull up and pull down resistor in microcontroller?
Pull-up and pull-down resistors are often used when interfacing a switch or some other input with a microcontroller or other digital gates. Most microcontrollers have in-built programmable pull up/down resistors so fewer external components are needed. It is possible to interface a switch with such microcontrollers directly.