Making hydroponic Nutrient Solution requires stirring the concentrated liquid solutions before they are added to water in the mix tank. To accomplish this I want to use a stir plate. This consists of a 80mm computer case fan with magnets glued (with E6000 adhesive) to the fan hub. In the container is a stir bar which also has magnets in it. The case fan is placed as close a possible to the bottom of the container while still allowing clearance.
The problem: Using a relay to just switch ON the case fan will cause the stir bar to dislodge from the case fan magnets.
The Solution: When the stir plate is to be put into operation the motor starts out at a MIN value of lets say 35%. This is because the fan motor wont start turning below this value. Then the value will slowly increase to a MAX value of lets say 85%. Operate at 85% for X amount of time then slowly ramp back down to lets say 25% and then OFF. I have a IRF520 mosfet device to handle the 12VDC motor.
What is needed: Can anyone show me the XOD nodes and their configuration that would be required to accomplish this task?