Heat sensor controled circuit

Hello guys so I have this he project that i have to do in uni and it's about creating a control circuit (analog one) and weve chosen a ujt-scr circuit we want to connect a temp sensor to it so when heat is above a level it lunches the circuit to deliver the current to a fan And when temp is below a curtain number is Lunches heating system and we ve made this design untill now not knowing how to progress more any help