This project builds up on our last project by reusing the thermometer we created. The thermometer is a key component of our thermostat as we use this to test the ambient temperature and switch the device connected to our Raspberry Pi on/off based upon this.
We will start by explaining the relay device.
A relay is a type of switch controlled by an electro-magnet. It allows us to use a small amount of power to control a much larger amount, for example using a 9 V power supply to switch 220 V wall power. Relays are rated to work with different voltages and currents; for example, the Seeed Arduino shield's relays can work with up to 130 V of AC power.
A relay has three contact points; these are Normally Open , Common Connection ...