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Author Topic: 74hc595 oe pin not working  (Read 941 times)
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You can get Anything you want... if you know where and in some case's how to ask... Electronics components... Certainly ANYTHING you could find in a catalog... Bare 100W LED's, $26.95, Free Shipping... All Day Long, ( $59.00 with the CC driver )... GREAT Project for an Arduino, a 100 W LED Dimmer, uses a 74HC595 and some small sensing resistors...

Doc
« Last Edit: June 29, 2012, 04:12:01 pm by Docedison » Logged

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Earlier today, I wrote:
Quote
If you promise to send me the two "bad-out-of-the-box" 74HC595's, I'll tell you how to get the other three to work.

Then some other clown said:
haha, and if you cant figure that out you can send me the other 3 ...

Maybe I'm too sensitive, but I'm thinking that somebody doesn't take me seriously here.

Here's what I think is going on:  you're driving the one LED that doesn't work from pin 9 of the74HC595.  Pin 9 is called "QH'" in this datasheet - http://www.sparkfun.com/datasheets/IC/SN74HC595.pdf - and its function is "serial data out."  The logic and timing diagrams show that it's not affected by OE, and it doesn't have a high impedance state.  If you drive an LED from this pin, you can't control it by pulsing OE.

I think that you want to drive that LED with pin 7, "QH," whose function is "parallel data out #7."  Pin 7 responds to OE just like the other seven parallel data pins.

Did that fix it?  Are you going to send my my shift registers?
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Good Call Really good. and more likely than my ideas about pull ups (was the mistake I made the most often, thinking that the processor was in a known state and letting it control the bus line instead of insuring that just in case it is in a known state)

Doc
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--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

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