I have an Arduino Uno. I need to use an electric linear actuator to control the movement of a joint in which I have installed a rotary encoder to know in what angles it's moving.
The actuator is a 12 Volt DC and has only two wires to control it, no libraries or anything. I have a 'double relay' which I think is useful to make the actuator run in both directions, but I'm not sure if I'm going to fry it or not. I also need to connect the arduino and the actuator to batteries or an outlet and I really don't know how NOT to fry them and this is my real problem right now since I don't know what kind of power source to use.
The encoder is to prevent the actuator to move between some angles and to measure the rotation speed, and the movement of the actuator is supposed to be controlled by two buttons, one to go forward while is being pressed, and the other to move backwards.
To picture the design a little better, imagine a leg in which the actuator is in the thigh and it pushes the calf in order to move the leg. The encoder is located inside the knee joint.
Best Answer
Without details like what actuator you bought or a datasheet it is a little difficult to give you exact information and guarantee its correctness. However we can do a bit of educated guessing.
If there are only 2 wires going to the actuator, note not 2 control wires but 2 wires total then we have to assume thats for power and ground. Power them one direction and the actuator moves power them another and it moves the opposite direction. We can determine the maximum current the actuator can consume by measuring the resistance between these 2 leads. 12volts/resisitance(in ohms) will give you the maximum current draw. So if you measure 1 ohm then the current draw is 1 amp for 12 volts.
This is way to much for the arduino to handle. If I were setting this circuit up I would use whats called an H bridge. However using relays might be a bit easier as a beginner. You will need 4 relays that way you can turn either wire positive or negative. Depending on the relay you probably will not be able to trigger it with the arduino directly... Hook one side of the coil to your 12 volt power supply and wire a logic level n channel mosfet up to the the other. Put a resistor between the gate of the mosfet and your microcontroller pin. That will allow you to turn the relay on and off with your arduino