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Topic: Can't turn on all LEDs in row using 7219 (Read 396 times) previous topic - next topic

Bob Applegate

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?

Bob Applegate

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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