how to connect an led using a pull up resistor

[K2DGR8]

Dear friends,

I want to connect an led to microcontroller using a pull up resistor..

But, when I give '0' to output port, leds will keep glowing because of the pull up...

Pls help me with the problem

 

[Li_ereunpisan]

try..look at this

View attachment led pullup.bmp

 

[keith1200rs]

You need to show your circuit.

Keith

 

[Tahmid]

Since you haven't shown your circuit diagram, I assume we're talking about a pin that is open-drain (or open-collector) and you want to use that to light a LED. In that case, have the LED connected between output pin and VDD/VCC. Send 0 to the pin to turn the LED on and send 1 to the pin to turn the LED off. You don't need the pull-up resistor. Of course you'll need to have a current-limiting resistor in series with the LED. However, you can not turn the LED on with a 1 if the LED is connected between the output pin and VDD/VCC. To turn the LED on with a 1, the LED must be connected between the output pin and ground.

This should make things clearer:

Hope this helps.
Tahmid.

 

[K2DGR8]

Dear friends,
I am trying to glow an LED from port 1 of 89C52 microcontroller.
I have arranged the components as shown in the ckt diagram in the last reply by Tahmid.

But, I am unable to glow the LED.
I also measured the voltage across the pin to which LED was connected (P1_5).
It comes out to be +Vcc.

But, the voltage across LED and resistor(470E) is 0V.

Can anyone help me with the solution?