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Topic: ShiftMatrixPWN problem leds do not fully turn off :( (Read 1 time) previous topic - next topic


Hello guys! I was wondering why my common anode rgb leds will not turn off fully with the ShiftMatrixPWM lib. The way I have it hooked up is the common anode of each led in each row is connected then controlled by the row pin. and the same thing for the col. When I measure the voltage out when its off its not putting out the 5v that it needs to turn fully off. It is putting out 4.55v on one of the red col pins when ShiftMatrixPWM.SetAll(0); Any ideas?


The way I have it hooked up is the common anode of each led in each row is connected then controlled by the row pin.
Hello JT, I would just like to confirm your setup. The ShiftMatrixPWM library uses two chains of shift registers. One to drive the columns and one to drive the rows. Your common anodes on the row should be going to a pin on the shift register. Depending on what size your matrix is, your shift register probably will not be able to source this much current so I would suggest using a PNP transistor to source the current.

As to your issue please make sure you have it setup correctly and that the settings inside the ShiftMatrixPWM script that you are using also have the correct settings for your type of matrix. There are settings for inverting the output to allow for different setups. If this is setup on a breadboard, check that all connections are in their proper place (its very easy to be out by a single hole and get very different results).

If you are still having issues then please try to provide so more information to go on and I will try and help.


Ok I now switched to ShiftPWM to see if I still have the issue with a dedicated pin per color and when ShiftPWM.SetAll(0); or ShiftPWM.SetRGB(0,0,0,0); is called it still does not turn off all the way. Instead it just gets dimmer. I attached a picture of my board, that is the led turned "off".


Fixed the issue, I was trying to use pin 11 as the latch pin.


Good to hear you got it sorted out. Would love to see a pic or video of the finished product running.


sure when I get it done Ill post here :D im making a LED table

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