89C51 (P0) Open Drain Problem

[Micro Lover]

hi
i m using 89C51, the 3 ports (P1, P2, P3) are used for different purpose, but the remaining port (P0) , the Open Drain, is remain, the problem is that, I want to use it for 15 different Lights, using matrix, (3 Rows and 5 columns) the 3 rows are positive volt and 5 are minus/ground (each pin used as switching)

using 5 volt signal, controlling 9 voltage, the hardware is designed with NPN and PNP transistor, the same hardware that i used in Port 1 and Port 2, is working fine, but here the port 0 is open drain, and i also used 10k pullup resistors, but its not showing/glowing any light.

 

[nigh]

please post a simplified schematic diagram of your setup. you can simplify it showing only one led. It would be much easier for us to understand the problem that way.

 

[FvM]

The below schema should work. Q1 could be omitted for 5V LED supply.

 

[Micro Lover]

here i tried to explain the problem

hi,

here i tried to explain the problem

View attachment untitled.bmp

Don't start new threads with the same content. Threads merged [alexan_e]

 

[E Kafeman]

Re: here i tried to explain the problem

Without ground reference can that circuit not do anything reliable. If it normally is working fine, what is the function of fine? Input/output is it logical DC levels?
If I add a ground ref. and guess type of input, output load and voltage swing does it result in that Q1 is missing a pull up resistor at base and Q3 can not close fully as base voltage is lower then 9V.
I am probably guessing wrong?

 

[FvM]

What's the use of a follow up thread?

Your original post is referring to a matrix circuit, it's unclear where the matrix connection is intended in your link. I'm keeping my suggestion for the time being.