uln 2003 not working

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Dalvir

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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
 

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.
 

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"
 
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    IanP

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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
 


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
 
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    Dalvir

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