Pull up resistor substitution ?

[Screech]

I've notice that most input/triggers to chips can use a 10 k resistor and some form of a switch.
Ive used 10k resistors, for timers, and some cmos's,and for a few other applications.
I think they are called pull-up resistors.

Anyway, what I want to ask is, can I change the resistor to a 5k?
Would it over load a chip?


Why do most circuits use 10k?

see my pic, which I want to change the resistor to 5k.
Thanks

 

[JimB]

5k will be fine.

10k is used because it is a common value (5k is not), and gives enough current to "wet" the switch contact.

JimB

 

[Screech]

cool, JimB
Thanks.

and gives enough current to "wet" the switch contact.

What do you mean by the wet part?

 

[mstechca]

I think 10K is the largest resistor you can use as a pull-up resistor in most applications. Don't go lower than 1K.

For the best resistances to use, check the datasheet for each semiconductor you are using (including transistors). The datasheet should at least indicate the maximum current the device can handle. Sometimes it indicates the minimum current required for the chip to function.

Now use ohms law to determine how much current your chosen resistance is giving to the chip.

 

[Someone Electro]

CMOS stuff works on voltage and not curent.This way it can also go from the suply voltage to ground.

by bipolar transistors you dont need this since there curent sensitive.

This wont give much curent.(CMOS consumes virtualy nothing so who craes)

 

[JimB]

cool, JimB
Thanks.

and gives enough current to "wet" the switch contact.

What do you mean by the wet part?

After a while a switch contact will start to become tarnished and the two parts of the switch will not make contact. This can be a problem when switching very low level audio and RF signals.
A current through the contact will "burn" through this tarnished layer. This current is usually reffered to as a wetting current.

For low current applications like this it is best to use contact with a gold layer on them.
However for high current applications the gold will soon get burned off, in which case you need to use a silver contact.

JimB

 

[Screech]

Pull up resistor substitution

cool. I get it.

I'm useing the gold contacts.

Thanks Guys.