PullUp and PullDown Resistor

[scientificpakistan]

Dear Forum Members,
I want to know about the basics of Pullup and Pulldown resistor. How they works, and how to calculate its values. Can anyone explain it pictorially.
I will be very much thankfull .

 

[Adnan Afzal]

Aoa,

check it out..hope u find it helpful https://en.wikipedia.org/wiki/Pull_up_resistor
Allah Hafiz

tell me if u need further help

 

[scientificpakistan]

Assalam-O-Alaikum!
Dear Adnan, I need further information regarding PullUp & PullDown resistors.
Khuda Hafiz

 

[kwkam]

V=IR that all

 

[auto_mitch]

**broken link removed**
http://www.personal.dundee.ac.uk/~gathomso/EG2103/pull-up.doc
http://www.interfacebus.com/IC_Output_Input_Pullup_Resistor_Values.html

Don't forget to press the helped button

 

[Meridian]

Dear Forum Members,
I want to know about the basics of Pullup and Pulldown resistor. How they works, and how to calculate its values. Can anyone explain it pictorially.
I will be very much thankfull .

Good answers and links!

Additionally, a pullup resistor is used when signal needs a little stabilization and strengthen the signal. I mainly only use pullups, not pulldowns.:|

 

[McShamrock]

Let me explain only pull-up, pull-down is the same but with reverse logic.
You have a bus, and a signal is required to by high voltage when its logical value is zero. If you have more than one device connected to the bus, each device must be open-drain (high impedance) in order to not interfer with others. This means devices only transmit when have a signal to send, that means transmit when have a logical 1 (low voltage) to send. When they have a low voltage to send, put their output to ground in order to put the hung pin of the pull-up resistor at ground. You need large resistors to have small currents (33K, 47K or 100k are really usual) thru the resitor when logic 1 is transmitted. If you have no more data to transmit, the devices enter in open drain and both the edge of the reistor result put at Vcc, then high voltage is seen.
That's all...

Bye,
N.

 

[rfzheng]

yes ,i see also, very good

 

[satyasiva]

the current flowing in the circuit decides the value of resistors.

 

[ravitest]

pullup resistor makes the output voltage to increase by passing current through it.
pulldown resistor makes the output voltage to decrease by passing current through it.

 

[smartdream]

**broken link removed**
http://www.personal.dundee.ac.uk/~gathomso/EG2103/pull-up.doc
http://www.interfacebus.com/IC_Output_Input_Pullup_Resistor_Values.html

Don't forget to press the helped button

very clearly explaination, thanks!