Hello! I have been lurking here for awhile. I have a circuit design question I am hoping someone can help me with. The scoop: I am building a device to allow me to remotely steer a trolling motor on my boat either manually or via autopilot from computer input. My progress: I have a programmable device to sense motor travel from a pot and apply a DC voltage (configurable from 1-12 volts) to drive the motor. To reverse motor direction, the device simply swaps the voltage. So I can control the exact position of a shaft on a motor, like a servo, only cheaper. My problem: My controller only outputs a max of 50mA. My steering motor - a power window motor for a car - draws from 3 to 10 amps depending on load. I need to build a small circuit that will take a +/- 1-12 volt dc input, draw under 50mA and switch the higher amperage load driven directly by my 12 volt marine battery. It also needs to reverse the polarity on the output voltage when the input voltage does the same. I considered using a couple of relays, taking care to make sure only one was on at a time, but I'm not sure that solution would be ideal. They would have to switch several times every second while making course corrections, and I'm thinking they would wear out fast. I plan to use this system for hours at a time, so I doubt the relays would last long. They may also take a bit longer than expected to switch - I need to switch this quickly, so the steering appears fluid. Is there a better solution I can use, other than relays? If nobody knows the answer to my question, could you point me in the right direction? Maybe a web site or something that will help me? I understand really basic electrical theory but I know little about circuit design. I can, however, follow a basic schematic and solder... Thank you!!