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Topic: 2 digit seven segment LED display  (Read 3431 times) previous topic - next topic


You can drive your digits with 2 shift registers in total. You you just need a few extra diodes for the corner leds. This might look slightly different than if you used more shift registers, but would keep your circuit simpler and for all I know perhaps more authentic.

The max7219 is a potential solution. You would have individual control of each led. However the brightness would be less due to multiplexing. This may be acceptable for indoors. It would also reduce the complexity of your circuit. One chip and one current setting resistor.


If you are going to use "ordinary" 20 mA LEDs, then MAX7219s would be the optimum solution.  You would have the chip drive each LED separately, no series connections, and it would strobe them at 40 mA to give excellent brightness (1 in 8 duty cycle, so actually averaging 5 mA but you also have brightness control).  Powered from a 5V supply.


Yes, my MAX7219 breakout board would be great for driving 40 LEDs.
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.


Thanks again guys for all the help. Its truly appreciated.

I'm putting together a final parts list and will be visiting www.crossroadsfencing.com on this Friday to purchase the MAX7219 breakout board.

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