Power PWM ControlBecause the power supply was running at 12 volts we needed ways to vary the voltage to the components in our system. The circuit shown to the left is a common MOSFET circuit and is what powers the hot wire and the fans. R2 is placed there to prevent the MOSFET ge pin from being overloaded with current. The other one is there so that the natural state of the MOSFET is off. This is important because if we were to give a PWM value to turn it on, it would just stay on, and we would run 12 volts instead of being able modulate between 0 and 12. The PWM signal controls voltage over R3 in the diagram. The PWM signal is being controlled by an Arduino which is the same Arduino that is controlling the LEDs.
We used a second Arduino because we wanted to separate the power system and the motor control system. This also allowed us to simplify the code so we did not have to juggle as much with one script on one Arduino. The power controller manages the fans, the wire, and the lighting in the project. The PWM signal sent to the wire system was controlled by potentiometer which allowed us to turn off the wire and still keep the rest of the cutter running.
The power supply has changed the most in the electrical system throughout the project.
At first the power supply was just a plug in power supply that can give enough power to supply the motor Shield and motors.
A laptop to power your doing Arduino Mega and the other Arduino.
Finally, a bench power supply to power the fan and the hot wire.
So once we decided our all of our components for the electrical system the power supply could be chosen so we have enough power for everything. We choose a 12 volt power supply that could give out 30 amps total. This was more than enough for the cutter to operate needing 15 amps in order to run.
To make this safer and more portable we add a socket with a switch on it in the back of our enclosure. This allowed us to use the switch to switch it on and off the power in a second. Also a detachable cable from the wall making it easier to transport while cover live 120 ac volt wires when running.