So you've made it this far, not only did you look into what a CNC is/ was, but you're interested in how they work.
The two more common methods for interfacing your computer to a CNC machine is the parrallel port or the USB (Universal Serial Bus) port.
What is the difference? How do they work?
Let's begin with the parrellel port The "parrallel serial port" connects directly to your computers motherboard threw a series of pins, a cable known as a DB25 cable connects to a PCB (Printed Circuit Board). This is how regular printers worked for many years, most of the 1990's style printers connected to the home computer using this approach.
The Parrallel Serial Port worked by sending electrical pulses threw the pins to the wire in the DB25 cable, the PCB directed the electicity as desined to control devices, the DB25 Parrallel Serial Port has 25 pins, out of those pins 8 are not connected to anything (plan for expansion), 9 where Negative, and 8 Ground (common AKA earth), another very common port still used by the monitor (LCD) is the COM port, it works the same way a DB25 does, the only variation being the pinout.
The USB (Universal Serial Bus) breakout board uses an IC known as a TFID chip, this IC acts as a DB25 does making the computer aknowledge the connection as being a COM connection in some applications. The USB sends data in packets to a Micro-Controller board that conatins the TFID IC, the Micro-Processor IC then runs firmware and decides what to do with the electricity. The Arduino PLC (Programable Logic Controller) has the FTDI IC, this PLC interfaces with devices using mulitle I/O (In and Out) connectors.
A Parallel Breakout Board connects to your personal computers parallel port by means of a cable. The breakout board sends electrical signals threw pins to screw terminals or boards with integrated circuits or other devices. Generally a DB25 connecter looks like the one below.
The screw terminal are used in point-to-point wiring to connect up the rest of your system. These are the most common, the hardware is generally inexpensive and easy to find.
The DB25 does have a few drawbacks, one being the parallel port itself most computers don't have a DB25 port or COM port, most are USB or Universal Serial Bus ports. Because of the lack of pins the USB must connect to an controller of some kind.
Another drawback to the DB25 and COM would be the limitation on performance, particularly when used with Windows software opposed to Lynux systems. You will be limited in how quickly you can send and receive the signals from the board, which may in turn limit the performance of your CNC. For most low end applications, or if you are using Mach3 with Windows, this is not a problem.
Get a few old electronics together, some breadboard, a soldering iron and start having fun!!
SOC Robotics provides a great quality product and the machines found on whatisacnc.com use the boards provided by the company. Check out pictures of the breakout board
A breakout board interfaces your computer with the outside world, it allows you to connect your computer to external devices like a set of lights, a switch, or a drill press. You can make your own or purchase breakout boards.
Here are a few for sale:
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So how does a breakout board work anyway?
The breakout board is used to interface between your PC and the various motor controls, relays, and other devices you want to control on a CNC machine. Four boards that interface your computer and your GUI with motors and switches outside of your computer are the Parallel breakout boards, USB breakout boards, Keyboard Emulators, and Motion Control Boards.
Next: How to make one!
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