I have a new SeeedStudio relay shield 2.0 4 channel relay shield I bought at Radio shack. when I have a power failure and subsequent restoration, the relay shield buzzes loudly when it the channels are not activated. Subsequently activating the 4 channels (turning them on with my controller) and it goes away. what frustrates me is this happens ever time power is lost to the device.
some background on use. the Shield is used to power some LED drivers. 5.5 volts in from an external power supply and then 5v pwm signaling from my controller (not Arduino) to activate the channels.