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. With 4 manual contrl keys,you can control the high voltage without program.
Note: Please note that the pins on relay shield should not touch the USB connector of Arduino UNO when they are connected.
Place 2 layers of electrical tape on the top of the Arduino's usb connector. This will prevent the relay shield from making contact. Do not operate voltage more than 35V DC.