Hi. I'm currently trying to build a circuit in order to control a small pump motor from an ardupilot mega 2.5 microcontroller. The pump is rated at 12 v and 3.6 w but I only need to give it about 9 v for operation. I'm using a basic supply of 9 v battery or 2 in series to give the power necessary. I've designed a basic bjt circuit that outputs the correct voltage I need in simulation and theory, but when I connect it to the microcontroller output pin, the ardu cannot sync enough voltage/current to give me the output I need to turn on the pump. I've tried buffering the input with an op amp and several different configurations on my bjt circuit. Can anyone please help me out with this? This is a rough schematic of the circuit I'm currently using: Thank you for any help.