Contents
- 1 Why is the pull-down resistor needed between the emitter and ground?
- 2 When using a pull-up resistor with a switch the switch has to be connected to ground?
- 3 How does a pull up resistor affect the input pin?
- 4 How does a pull down resistor work on a microcontroller?
- 5 How does the pull up resistor work on a VCC?
Why is the pull-down resistor needed between the emitter and ground?
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.
When using a pull-up resistor with a switch the switch has to be connected to ground?
They operate using the same concepts, except the pull-up resistor is connected to the high voltage (this is usually 3.3V or 5V and is often refereed to as VCC) and the pull-down resistor is connected to ground. Pull-ups are often used with buttons and switches.
Why totem pole is used in place of passive pull up resistor?
If you use the totem-pole, you don’t need to rely on the pull-up/pull-down resistor and that gives you advantage in better current handling, better driving of capacitive loads, MOSFETs, etc.
How does a pull up resistor affect the input pin?
With a pull-up resistor, the input pin will read a high state when the button is not pressed. In other words, a small amount of current is flowing between VCC and the input pin (not to ground), thus the input pin reads close to VCC.
How does a pull down resistor work on a microcontroller?
A pushbutton switch is connected between the supply voltage and a microcontroller pin. In such a circuit, when the switch is closed, the micro-controller input is at a logical high value, but when the switch is open, the pull-down resistor pulls the input voltage down to ground (logical zero value), preventing an undefined state at the input.
Why do you need a pull up resistor on SparkFun?
When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin. For condition 1, you don’t want the resistor’s value too low. The lower the resistance, the more power will be used when the button is hit.
How does the pull up resistor work on a VCC?
When the button is pressed, the input pin is pulled low. The value of resistor R1 controls how much current you want to flow from VCC, through the button, and then to ground. When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin.