Step 10: Automatic Switching Circuit Design
This circuit has only one major part: a double pole double throw relay. It is wired in such a way that it will automatically switch the output whenever the inverter is powered on. To achieve this, the input line from the wall outlet is connected to the normally closed contacts and the output line going to the appliance is connected to the common contacts. Then the input line from the inverter is connected to both the coil and the normally open contacts.
When the device is inactive, your appliance will be connected to the wall outlet and powered by the grid as it normally would be. The only difference is that it is going through the relay. But when the device is activated, the inverter turns on and sends power to the normally open contacts and the coil. This switches the relay. The appliance is disconnected from the wall outlet and connected to the inverter. This is how the switching circuit will automatically switch to your renewable power source whenever it is available.