External Pull-up resistor or Internal Pull-up resistor ?

Using Arduino General Electronics
1

hello guys,
i would like please to know which method is better for un-floating an input pin :
1- using the internal pullup resistor of the ATmega ?
2- using an external 10K resistor connected to +5V ?

2

I usually use the internal resistor, one less component.

3

LarryD:
I usually use the internal resistor, one less component.

ok thanks for reply, i do too but it's like i got curious to know if there is any disadvantages for internal pull-up

4

firashelou:
ok thanks for reply, i do too but it's like i got curious to know if there is any disadvantages for internal pull-up

If the wires on your data lines are really really long then the internal one may not be strong enough.

5

Delta_G:
If the wires on your data lines are really really long then the internal one may not be strong enough.

aha ok thanks for that info, will take note about it :slight_smile:

6

Mind you one of the more important matters is "lead dress" - all wires must be bundled into cables, either using multi-conductor cable or by lashing individual wires together.

Interference pick-up is via two processes, magnetic induction into any place where a loop forms, and electrostatic or capacitive coupling where wires are away from an effective ground. Both of these are minimised by keeping wires close together.

7

Paul__B:
Both of these are minimised by keeping wires close together.

I know what you mean Paul but that statement is open to misinterpretation.

Keeping data lines close to the ground return helps but keeping data lines close together and away from ground can result in crosstalk. Best solution for long data wires is twisted pair with each data line having its own ground return or balanced driving.

Russell.

8

Paul__B:
Mind you one of the more important matters is "lead dress" - all wires must be bundled into cables, either using multi-conductor cable or by lashing individual wires together.

Interference pick-up is via two processes, magnetic induction into any place where a loop forms, and electrostatic or capacitive coupling where wires are away from an effective ground. Both of these are minimised by keeping wires close together.

i am sorry Paul, but i did not get what you mean here :confused: