This Arduino Linear Actuator Tutorial shows how to do basic manual control of a large linear actuator using an Arduino and two buttons. In the first set of code, the first button extends the actuator and the second button retracts the actuator. In the second set of code, the two buttons move the linear actuator to preset positions.
Large linear actuators traditionally have five wires. Two wires are for powering the motor and three wires go the internal potentiometer for reading position. The two relays are used to toggle the positive and negative power to the motor in order to determine the direction of piston travel. The first bit of code doesn't use this, and the second uses this to reach a goal position. Let's get started.
It is suggested that you use the parts listed here to follow along in this tutorial. If you already have a large linear actuator, you can likely follow this tutorial to make it work, but you may have difficulty wiring for the potentiometer.