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The Relay Shield is an Arduino compatible smart module with 4 mechanical relays providing an easy way to control high voltage. The max switching power is 35VDC 70W for each channel. It can be directly controlled by Arduino/Crowduino through digital IOs with external 9V DC supply.
Placing 2 layers of electrical tape on the top of the Arduino's usb connector will prevent the relay shield from making contact. Do not operate voltage more than 35V DC.