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The MCU connects to PORT-C2. The problem with this is that when the MCU is not driving a voltage to the output pin, it gets pulled up to +12V by the 10k resistor. This means that if left unconnected (or the MCU goes crazy/dies) the MOSFET defaults to the "ON" state.
You can make this circuit work with a default "off" condition by using a P-channel MOSFET.
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With that circuit setup, a high gate voltage (approximately = Vsupply) makes the MOSFET be in cutoff. When you turn on the NPN from the MCU, it pulls the gate voltage down, which makes a P-channel FET start to conduct and turn "on".