What this 3D printer controller board?

Every 3D printer require a controller,  either it a dedicated microcontroller board such as Arduino and Arduino derivative board or your PC.  The main purpose of the 3D printer controller is run software that convert Gcode to electronic signal that drive stepper motor or the control plastic extruder.  Think it as a command interpreter.

Here is the key component of a typical 3D controller board:

• Computer or microcontroller that run the printer control software, normally this software is call printer firmware.
• Motor control board for 3D location and extruders.  if you have have more the one extruders then you may need more controller board.  
• Temperature Sensor for the extruder and heat bed.
• SDCard support for printing file storing and retrieving.
• Power on/off switching for Heating as well as fan.
• X, Y and Z end-stop to tell the software where the printer head is located at start.

Above diagram show an typical arrangement how the part is connected to the controller.  Sensor like temperature is read using A2D (analog to digital convertor).  Normally the heat sensor use is Thermistor, need to be careful on which thermistor you are using, difference thermistor have difference temperature table.  Make sure you are setting the correct table in your firmware configuration file, else you may overheat or underheat you extruder due to wrong temperature reading.  It the most common mistake make by a new builder.

Heating element like resistor, nichrome wire and recently cartridge heater is driven by the microcontroller PWM signal, PWM is very common method of controlling the amount power to a load without incurring losses. Think of it as a method to control temperature and typically the PWM signal is connected to a MOSFET device that act as switch that connect the heating element to the main supply. e.g.12v or 24v, so that it can drive with full power from the main.  Controller also run PID routine for better temperature stability.  There also have a Gcode to help you tune your extruder.

GPIO is use for taking input signal from the X Y and Z start location switch, and to send control signal to motor controller.   Will have a dedicator discussion on the motor controller and motor itself, since it very importance subject that need more clarification.   Your print quality is depended on you motor!!! So be really careful on you Motor configuration.

I leave out feature such as networking and SDcard support, both very nice to feature but really needed for typical operation.