For a project, we (students) want to demonstrate the principle of PID to control the temperature of a room. Instead of using an entire room, we will make a "sample setup": namely a box with temperature sensor and a 220V AC heating element in it (probably coming from a hair dryer, or another home or kitchen appliance). And with a fan in it, to spread the temperature.
We will use an arduino, with the PID library, and we will connect that to a Solid State Relay (SSR).
However, it seems that we can use two types of solid state relays: zero-crossing or random turn-on... Which type should be chosen?