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Author Topic: Can't turn on all LEDs in row using 7219  (Read 141 times)
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Bob Applegate
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« on: April 11, 2013, 04:18:03 pm »
 Bigger Bigger Smaller Smaller Reset Reset
I have a large 5x7 LED array connected and am using the LedControl library.  I can turn on every LED in a given column, but only four in a given row at a time.  Turning on more than four causes the LEDs to briefly light up (just a flicker) and then all go off again.  All LEDs can be turned on/off, so the LED matrix appears to be functional.

This sounds like a current issue, so I turned down the intensity (software control) to 1/2 of the value but the same exact thing happens. 

My current limiting resistor is 10k.  Am I exceeding some maximum for the chip?  I would have expected the LEDs to dim, not flicker on and then turn off.

Any ideas?
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Bob Applegate
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« Reply #1 on: April 11, 2013, 10:05:15 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Found my own problem.  The current limiting resistor needed to be larger.  Increased it until the problem went away, then increased a tad more for good measure.
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