I'm designing a PID temperature controller for a laser diode with arduino. The laser gives me the value of its temperature, which I compare with my reference and then, through the controller implemented in arduino, I'll obtain the proper output values in volts.
The way the laser increases or decreases the temperature is by a peltier cell. So applying a current through this cell it will change it (to the correct value if the PID is set-up properly).
The thing is that the current has to be positive or negative, depending on if we want to heat the laser up or cool it down. I don't know how could I get those currents from the voltage values obtained in arduino.