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Topic: using a 4 digit LED number display? (Read 3 times) previous topic - next topic

fyrebug

Jul 06, 2009, 05:41 pm Last Edit: Jul 06, 2009, 06:03 pm by fyrebug Reason: 1
I have the following led display from sparkfun.
http://www.sparkfun.com/commerce/product_info.php?products_id=9214

trying to build a clock for fun.

the issue is I can only get it to display all the same numbers 33:33 44:44 etc...

has anyone used one of these before and have any pointers on how to get different numbers? the spec sheet got me as far as the base numbers, but I can't understand it well enough to see how to do multiple different ones.

thanks!

Mike Mc

Your multiplexing the display right?

How do you have it wired up?

fyrebug


fyrebug

ahhh multiplexing!
http://www.youritronics.com/seven-segment-display-explained/

and for any others wondering...

not sure if I have it hooked up correctly, but now I'm starting to understand the idea of it atleast.... having trouble getting the leds numbers to not all turn off though

pwillard

#4
Jul 06, 2009, 08:42 pm Last Edit: Jul 06, 2009, 08:43 pm by pwillard Reason: 1
Well, that  explains why you get what you get.  The DISPLAY is wired so all of the LED segments a.b.c.d.e.f.g are wired together on each DIGIT.  the other side of the LED segments are wired to a common pin for each digit.  When you multiplex, you are only driving one digit at a time... not all at once.

Sequence:  

SET A-G SEGMENTS for DIGIT 1
ENABLE COMMON PIN for DIGIT 1
SET A-G SEGMENTS for DIGIT 2
ENABLE COMMON PIN for DIGIT 2
SET A-G SEGMENTS for DIGIT 3
ENABLE COMMON PIN for DIGIT 3
SET A-G SEGMENTS for DIGIT 4
ENABLE COMMON PIN for DIGIT 4
back to digit 1

IN ALL CASES you turn on A-G segments with the same pins.  You enable digits with different pins.

Do this REAL FAST and persistence of vision will make it look like they are all on at once.

Rather than my try to explain it...  read what this guy wrote:

http://www.youritronics.com/seven-segment-display-explained/

EDIT:  Oh  cool, you already found it

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