Hey, I'm rebuilding a magnetic stirer i bought from aliexpress. On inspection it was just a dinky little transformer with a discreet bridge rectifier running into a very basic lm315 circuit to adjust the speed of the motor. I've completely ripped out everything and rebuild it. I'm just stuck on the heating element. The element itself is straight across the mains (240v) It measured around 370ohms, 155w. I would like to make the heating output adjustable but don't know where to start, any ideas?