So now we connected a very High value resistor from the floating node to Ground. So after connecting to a Pull down resistor the Fig 1 will look like as follow: Pull down resistor will pull a floating node to logic level low i.e. Everyone connecting a switch to a microcontroller must avoid these configuration for their switches. So it may lead to ambiguous readings from the switch. So we can see that, if we use the Switch as input device to a microcontroller in these configuration, the device is going to face some undefined states (Floating State). Similarly for Fig 2 we can write the table as Switch_State So we can write the states of Input Pin based on switch state as: Switch_State We can’t be sure about the voltage level of the Input Pin.
But when switch is open (Not pressed), state of input pin is undefined. When the switch is pressed, voltage at input pin will be equal to VCC. The pull up and pull down resistors are used for preventing a node from floating. So in this article I am going to explain you the concept of Pull-Up and Pull-Down resistor, their significance and their working. That post ignited me to write a small article explaining this concept. I came across a post which was related to Pull Up resistor. It is related to Microcontroller based projects. Today I was visiting a group on Facebook.
