uln 2003 not working

[Dalvir]

i use uln2003 to drive the 7 segment i connect the pullup(10k) to 8051 port0 and it connect to the uln2003
i check the voltage it 4.9v when i place the uln 2003 in the circuit it drop the port0 voltage to 2.5v i change the uln2003 ic but the problem still arrive
pin 8 of uln2003 is ground 9pin is connect to +5v
i connect pin 1 of uln20003 to gnd then the out put is at pin 16 is 200mv
whem pin 1 is connected to +5v the out put is at pin 16 is 0.5v

 

[amayilsamy]

Disconnect the 9th pin from 5 V Vcc. And Check it.

How many 7 Segment you interfacing?

Post your schematic here its much easier to solve it.

 

[dimas_lilik]

Dear Dalvir,
ULN2003 and ULN2004Aare high voltage, high current darlington arrays each containing seven open collector darlington pairs with common emitters.
I hope you know "schematic open collector"

 

[Dalvir]

i have 2 7segment
i also remove supply from 9 pin but voltage drop still remain
i check 7 segment bu shorting 1pim by 16; 2by 15 it work i use common cathode 7segment

 

[IanP]

i use uln2003 to drive the 7 segment i connect the pullup(10k) to 8051 port0 and it connect to the uln2003
i check the voltage it 4.9v when i place the uln 2003 in the circuit it drop the port0 voltage to 2.5v i change the uln2003 ic but the problem still arrive
pin 8 of uln2003 is ground 9pin is connect to +5v
i connect pin 1 of uln20003 to gnd then the out put is at pin 16 is 200mv
whem pin 1 is connected to +5v the out put is at pin 16 is 0.5v

2.5V at any of the ULN's input while hooked-up to +5V via a 10k resistor is just fine - have a look at the internal circuit: 2 x U[BE] + U[2.7k] ..

Keep in mind that the outputs are OC [open collector]. Measuring voltage without any pull-up load is pointless. As a test, connect a 1-10k resistor to pin 16 and perform test with +5V and 0V connected to pin 1 again ..

:wink:
IanP