Friday, November 7, 2008

9 Pin dot matrix printer using PIC16F84A

In this project we design 9 pin Microsoft Windows NT compatible dot matrix printer using two PIC16F84A microcontrollers. Printer mechanism is based on old Commodore dot matrix printer. At the moment this device support for Microsoft Windows 2000 and XP operating systems.

Other most notable features of this implementation are,

  • Drive 18V - 9pin magnetic dot matrix head unit

  • Handle 12V paper feeder and head movement stepper motors

  • Support A4 and compatible page formats

  • System drives using 240V - 18V step-down transformer

  • Audible warning system

  • Low power consumption due to CMOS implementation

  • Works with Standard Printer Port

In this implementation we use Microsoft Windows Driver Development Kit (DDK) with Microsoft Visual C++ to create device driver for the system and use Delphi 7 to create front end application (printer maintenance – control panel applet). Both microcontrollers are programmed using MPLAB – ASM.

In this system we use 2 microcontrollers with 7MHz oscillators,

One PIC16F84A handles all incoming messages from LPT port and send status information to the port. This MCU also provide front end interface to the system (such as manual paper feeder switch, audible warning system, etc)

Second microcontroller handles printer head and paper feeder.

Other than PIC16F84s we use following semiconductors in this project,
  • Series of ULN2001 chips to interface system with printer head and stepper motors.

  • MC14066 as virtual switches

  • NE556 for audible warning system

  • LM317, LM7805, LM7812 power regulators

  • 18DB05 Bridge rectifier module
During the test runs this printer produces an excellent results and only most notable limitation is its slow speed in printing. In future we plan to implement USB and Ethernet interfaces to this project.