Juan Carlos wrote:
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Hi, I have a project where the LPC932 opens and closes a mechanic solenoid valve through a relay, which inverts the polarity. Sometimes I get some "noise" and the micro controller starts oscillating. I have a RC filter at the Vcc line on the micro. The oscillation starts when I have the solenoid valve connected to the circuit. Otherwise the circuit works as expected. I know this is a software forum, but I thought maybe someone would have any idea on how to approach this issue. I need to prevent this oscillation when the solenoid is connected to the circuit.
Thank you
Hello,

The problem is probably that the voltage when opening your solenoid goes into the power supply. This creates a peak voltage on the power supply and the microcontroller is disturbed...

A freewheel diod should be implemented on your relay to avoid this on the relay and your solenoid shouldn't be supplied with the same power supply thant the microcontroller.

Usually, what is done is to supply the solenoid before the voltage regulator of your microcontroller and after a serial diod and with an electrochemical capacitor.

Regards
Stephane