Switching the relay coil generates a large inductive electromotive force. A surge suppression circuit is often connected in parallel with the relay coil to suppress this electromotive force. However, if this suppression circuit is not suffcient, it may cause other electronic circuits, such as micro controllers to malfunction. Add an appropriate absorption circuit to prevent this problem.
 

Connecting or disconnecting a high current load with the relay contacts generates an arc discharge. This discharge may cause other electronic circuits, such as microcontrollers, to malfunction. Therefore it is necessary to take appropriate measures to prevent this phenomena.
 

Magnetic flux leakage exists in the vicinity of the relay in the energized state. Mounting a magnetic sensor, etc. close to the relay may cause it to malfunction.