LEDs and Multiplexing
Topic: multiplexing MAX7219
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Mar 29, 2013, 09:15 pm
: Mar 29, 2013, 09:23 pm by f_giorgio
Hi, I'm trying to multiplex 2 series of 7 leds, it's a test for the circuit that I'm going to use in another project in which it pilotates 3 or more seven-segment display.
The circuit is linked below, I need darlington's array because in the original project I use 12V to turn on the leds (more leds for each segment). The problem, visible in the video, consists in the the leds that should be turned off, but this doesn't appen completely. I've used
library with the example code showed in the same page.
I've tried to insert a push-down resistence on the UDN2981 outputs but it resolve the problem only on the second output. I've tried also another chip, and converting the circuit in common cathode form replacing the ULN2003 with UDN2981 and the UDN2981 with ULN2003. I've tried also to put the two condensator explained in the playground page at the input of the MAX7219 but nothing appens.
Thank you for the help and sorry for the english.
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