I am working on a project where mains voltage is first converted to 12 v and then it is converted to 5v for the arduino by a Buck converter. However, this Buck converter makes a weird sizing sound as soon as I connect the arduino.
My question: Is this normal or shouldn't it be? If this doesn't work out, how can I fix it?
It's probably the inductor resonating the PCB - higher frequency switching supplies tend to be less audible, although some drop frequency into the audio range when lightly loaded.