74HC595A Shift Register Outputs Low Level?

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Markkim
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74HC595A Shift Register Outputs Low Level?

Post by Markkim » Wed Apr 07, 2021 2:03 am

Hi
I'm working on a project, prototype everything on a breadboard and after testing soldered everything on protoboard.
I used the TI 74HC595 chip (component data source reference: https://www.apogeeweb.net/productdetail ... 8-scb80erz) in my prototype, I wanted to have everything on a PCB so I built schematic and ordered PCB with SMD assembly from JLCPCB.

Now I got the PCB and couldn't figure out why my leds are not working, tried to measured the voltage that the shift registers output and got very small voltage (less then 1 volt I think).

Is there anyone have ideas of it? I cannot get high voltage (>3v) in order to drive a led? Many thanks.

dyarker
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Joined: Fri Aug 22, 2003 1:01 am
Location: Izmir, Turkiye; from Rochester, NY
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Re: 74HC595A Shift Register Outputs Low Level?

Post by dyarker » Wed Apr 07, 2021 8:21 am

You need a better spec sheet, like -
https://www.onsemi.com/pdf/datasheet/mc74hc595a-d.pdf
(not from TI, but is for the "A" part (74HC585A))

Also needed -
A schematic diagram of your circuit.

My first EWAG based on limited info provided is OUTPUT ENABLE pin needs to be pulled up.

side comment - This is more a hardware question than computer programming. How did you pick here to post it?

Cheers,
Dale Y

dyarker
Posts: 1761
Joined: Fri Aug 22, 2003 1:01 am
Location: Izmir, Turkiye; from Rochester, NY
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Re: 74HC595A Shift Register Outputs Low Level?

Post by dyarker » Sun Apr 11, 2021 5:07 am

4 days. It was output enable?
Dale Y

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