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Topic: Understanding the components of a LED matrix (Read 2102 times) previous topic - next topic

dhenry

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But I'd like to...


The other option is to wonder.

CrossRoads

#16
Dec 25, 2012, 05:18 am Last Edit: Dec 25, 2012, 05:22 am by CrossRoads Reason: 1
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:
ATmega48A/PA/88A/PA/168A/PA/328/P:
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."
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

M4573R

Thanks Crossroads! That's looking exactly like what I'm after!

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