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Author Topic: Understanding the components of a LED matrix  (Read 1842 times)
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But I'd like to...

The other option is to wonder.

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You can use PNP transistorst to drive the anodes like this.
Or, skip the PNP, and use high brightness LEDs (6000-8000mCD) with 8-10mA from the 74HC595.
Or, skip both and drive the Anodes with 20mA direct from the Arduino, and spread the current over a couple of ports to not overstress any one port:

"3. Although each I/O port can source more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state
conditions (non-transient), the following must be observed:
1] The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not exceed 150mA.
2] The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 150mA.
If IIOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current
greater than the listed test condition."

* 8x8array74hc595uln2803.jpg (79.91 KB, 960x720 - viewed 17 times.)
« Last Edit: December 24, 2012, 11:22:43 pm by CrossRoads » Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at
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Thanks Crossroads! That's looking exactly like what I'm after!

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