“Relays are always used for AC switching circuits…we frequently need AC loads like Fan Bulbs to operate automatically with conditions like decreased light, increased temperature, etc.Also we come across situations like when we need to control appliances remotely using smartphone or we have sensor that detects human presence and turns on light ,fan and turns off when it is not detected..in all these applications we use a Relay board and we are now going to make such a Relay board that can be used along with logic circuits or micro-controllers to handle AC loads or High voltage DC loads..”