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Hi, My question in a general question about reducing noise in a hardware design. Is there a guideline to follow in order to reduce effect of external noise such as electropump or electric valve which is driven by an MCU using a relay? I am using STM32L152VD LQFP100 running with 16MHz internal oscillator. one of the serious things I see is effect of main power plugin to keypad input of MCU such that it is like a button is pushed when I plug in the 220V switching adapter power. Next is when MCU controls an electric valve in start or stop moment such that it is like a button is pushed. I have used same capacitor and resistor as in discovery board used for push button and used EMI ferrit filter around input power (5V) to my board. I used ferrit bead in series with main VCC of the board. should I used ferrit bead for all interrupt input and all VCC pins of the MCU? is there any other advice like a specific filter?
I collected my hints here www.8052.com/faqs.phtml