Why Won't My 74HC595 Shift Register Outputs Turn Off?

[David lopez]

I bought a 74hc595 shift register.
The 1st output and 2nd output won't change. They turn on two diodes and none of them will turn off. How do you get the 1st output
To output a zero? I have studied the
Datasheet doesn't help.

 

[lewando]

I can't figure out how to help you because you have not provided much to go on. Can you provide a schematic of your circuit? Did you overstress the SR? Hopefully you didn't buy just one.

 

[David lopez]

I think this file has a schematic of shift register.

 

[phinds]

I think this file has a schematic of shift register.

That's not what was asked for, that's just the shift register. What is YOUR circuit than includes the shift register? If you have nothing but the SR, it will just sit there like a lump.

 

[David lopez]

I connect output q0 and output q1 to
Leds. I connect ser input to negative
Terminal. G input to negative terminal.
I connect sclr input to positive terminal
To pulse high. I briefly connect sck input to positive terminal to pulse high.

 

[Baluncore]

You must use SCK to edge clock SER data into the 8 bit serial register.

You must then clock PCK once to transfer all 8 serial data bits into the parallel output register.

If you enable the drivers with Gbar, and disable reset SCLbar, then data will then appear on the outputs,

 

[Tom.G]

Once you have loaded bits into the shift register (the first column of flip-flops on pg.2 of the data sheet) with SCLK, you must then transfer those bits to the second column of flip-flops by toggling the RCK input, pin 12.

The reason for the second column of flip-flops is to keep the output data constant while shifting in new data. The RCK loads the data from the first column into the latches of the second column.

Cheers,
Tom