LED Multiplexing approaches - what's best?
NetHog
Posts: 104
I have going a nice 27-LED cube displaying a sequence of patterns. I'm actually right now leaving it running with a 9V battery to see how long it lasts before the battery is drained out.
With this cube, I have Anodes tied to 9 lines (through resisters), and Cathodes to 3 lines. With this method, I drive 9 LED's at a time,·each via a 470R resister at 5V this requiring SX to drive no more than·60mA. So far so good.
it occurred to me that there is a couple of variations in the approach on the SX
1) Drive the Anodes '1' for on, '0' for off, Cathodes '0' for on, '1' for off. This is acceptable as typical max reverse voltage on the LED is 5V.
2) Set all Anodes output to '1', all cathodes to '0', and set the SX pins to output for on, and·input (floating) for off.
Although the 2nd approach works, and on face value, does not rely on the reverse-voltage characteristics of the LED's, I'm curious if anyone has looked into the pro's and con's of the two approaches.
I will at some point post the pics / circuit for the cube in completed projects section if anyone is interested.
·
With this cube, I have Anodes tied to 9 lines (through resisters), and Cathodes to 3 lines. With this method, I drive 9 LED's at a time,·each via a 470R resister at 5V this requiring SX to drive no more than·60mA. So far so good.
it occurred to me that there is a couple of variations in the approach on the SX
1) Drive the Anodes '1' for on, '0' for off, Cathodes '0' for on, '1' for off. This is acceptable as typical max reverse voltage on the LED is 5V.
2) Set all Anodes output to '1', all cathodes to '0', and set the SX pins to output for on, and·input (floating) for off.
Although the 2nd approach works, and on face value, does not rely on the reverse-voltage characteristics of the LED's, I'm curious if anyone has looked into the pro's and con's of the two approaches.
I will at some point post the pics / circuit for the cube in completed projects section if anyone is interested.
·