Troubleshooting • how to get rid of false trigger using edge detection

Hello,

I am disparate in need for some help.
Information about setup:
I'm using a raspberry pi 4 on which is installed mycodo (a software for environmental control using sensors/relays, etc.).
Using that software to monitor for button presses using edge detection I can activate different relays and leds (which are connected via I2C).
There are 22 buttons connected to different pins on the raspberry pi. Basically all pins except GPIO 2 and 3 and GPIO 23 and 24 which are used for I2C, GPIO 27 and 28 which are not used at all, are used as inputs for buttons.
There is a separate PCB which is connected through a 20cm 40pin ribbon cable with the raspberry pi. On that PCB are the resistors and capacitors for the buttons.
The buttons are currently connected to in a pull up configuration using 1k and 1.8k (was 10k) resistors with 100nF capacitor to ground.
The raspberry pi is powered from the original/official power supply.
The PCB is powered via an IKEA - 3 port USB adapter.
PCB and Raspberry pi ground are connected together.

Problem: I get false triggers when quickly inserting and removing a empty extension power cord from the same socket which powers the raspberry pi.

Things I've tried and didn't helped:
- changing from pull down to a pull up configuration
- reducing resistor value from 10k to 1k
- installed EMI filter
- installed isolation transformer
- using shorter ribbon cable (2cm)
- using schmitt trigger CD74HC14E
- using an UPS, - the issue does not occur when the UPS is disconnected from the socket, but powering the Rasbperry pi or the PCB via a power socket would trigger those false edge detection.
- disconnected all cables which are connected to the buttons

If possible please suggest a hardware solution...
Please let me know if/what additional information is needed.
Picture with PCB and schematic (using pull down configuration) attached.



Thank you very much.

Statistics: Posted by F_trigger — Thu May 23, 2024 7:38 pm

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