I used its with four diodes and after 2-3 min of use the case became very hot. And the speed of the motor also increased. So removed the diodes and added a LM2596 DC-DC step down module. Unfortunately the module was too big to fit in the case. so I added the module in line with the wires and covered it with 25mm shrink tube covered the ends with hot glue. I made a small cut for the small screw on the pot in the module. Now its perfect. I can adjust the speed very easily and not parts are getting heated.