We've chosen not to have a fan on the ceiling since we'll be putting in a "moonroof". Obviously, we still need a way to circulate air. So, what we've come up with is this...
Remember those 2 round holes we drilled in the bottom on the floor? Those will chamber up to 2 computer fans which will be in a box directly at the front of the trailer. In addition to the fans, this box will house all the switching for our reading lights, etc.
Basically we have a fan regulator which needs a 5V supply in order to turn on the touchscreen screen and the control. Also needs a 12V supply to power the 2 12V fans. The touchscreen module has the capability to select the speed of each fan individually as well as monitor 5 different temperatures.
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Here are the 2 regulators. The input is going to be connected to the main battery and the 2 regulators are going to be able to regulate the voltage to create a 12V and 5V power supply.