Electronics > Beginners
AC Ripple in DC Line
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Twoflower:
That definitely looks like a not sufficient ground to the MCU board. To be on the save side connect all GND pins of the MCU. With most current going through the GND pin(s) it is not that important but a good idea to also connect all of the supply pins. With the additional grounding the Scope measurement is probably useless as I expected to see what the wires helped with.

Yes the ground is sometimes overseen. And it is as important as the VCC routing. In your specific design the GND is more important as the current running through the IO pins adding to the MCU supply. So a much higher current is running through the GND pin. Also you should check, if the MCU allows such load at all. Sometimes they say a single pin can drive up to xx mA but the maximum total is lower than the sum of all outputs at this max current. Ant longer wires might create additional load above he static current the LEDs need.

So probably it's worth to think about an additional driver stage. That driver would also make the setup more robust as they come with better protection circuits build in.
kony:
Please don't get bitten by the sunken costs fallacy. I am suggesting PLC as very feasible option how to get stuff done in almost guaranteed reliable way. Judging solely from the schematics you had posted, there is much left to be desired for it being called industrial grade design or ruggedised. Ladder might look bit dated and cumbersome to work with, but it gets the job done.
Blade2021:

--- Quote from: Twoflower on April 16, 2018, 06:13:11 pm ---That definitely looks like a not sufficient ground to the MCU board. To be on the save side connect all GND pins of the MCU. With most current going through the GND pin(s) it is not that important but a good idea to also connect all of the supply pins. With the additional grounding the Scope measurement is probably useless as I expected to see what the wires helped with.

Yes the ground is sometimes overseen. And it is as important as the VCC routing. In your specific design the GND is more important as the current running through the IO pins adding to the MCU supply. So a much higher current is running through the GND pin. Also you should check, if the MCU allows such load at all. Sometimes they say a single pin can drive up to xx mA but the maximum total is lower than the sum of all outputs at this max current. Ant longer wires might create additional load above he static current the LEDs need.

So probably it's worth to think about an additional driver stage. That driver would also make the setup more robust as they come with better protection circuits build in.

--- End quote ---

Hello there!,  I have an update.  Everything is working great!  I did find more noise in another machine that was causing similar issues but I traced it to a bad solder point on one of my support capacitors.  No more noise, no more issues.  Thanks for your help.

- Matt
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