Wanted: Heated Bed with stand-alone controller. DIY?

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So for this effort we will need the heatbed whichever you choose and wherever you get it. And then we will need a medium, that is a device that can interpret the controllers signal and translate it into power sent to the bed. An external Mosfet like this should do the trick: https://www.ebay.com/itm/Heating-Con...sAAOSwiaVeJTnV Once we have the bed and an external mosfet and I am assuming the bed has its own thermistor for temp sensing. If not then we will need to source that part. The thermistor can be fixed to the tiny hole in the center of most heat beds with a piece of Kapton tape. If needed it can also be sourced on ebay. So once we have the controlled circuit and the sensing circuits complete, that is the bed wired to the mosfet, power wired to the mosfet, and just the signal wires to the mosfet and the temp sensing wires left to connect to a controlling circuit, from this point we can choose a bulky Arduino nano or uno or w/e OR we could go with something small and efficient like a picaxe ic. In this rudimentary setup we can install a switch to ground or power as an input to select between 2 pre determined temps and you will write a sketch or program the microcontroller to achieve whichever temp as per the switch position. period. And you will have this controller power up at the start of your print. Of course the far simpler way is to upgrade the mainboard and wire that into the mosfet. No switch is needed then and we can achieve whatever temp we want for the bed whenever we want it.