Optically Isolated LPT Breakout Board for CNC & Routers

LPT Breakout Board for CNC & Routers

Optically isolated parallel port  break out board designed for Hobby CNC, Routers and Motion controller, This Board is an easy solution to drive stepper Motor driver through PC parallel port, The Board is compatible with various CNC software specially made for LPT port data output. The board has been tested with MACH3 CNC software.   All outputs are optically isolated and inverse, all inputs are optical isolated and can be used as emergency switch, limit switch, home switch and feedbacks. The Opt coupler and inverter require power supply at both PC side and output side. USB connector and CN5 Screw terminal provided for PC side power supply input and CN4 for output side power supply 7 to 36V DC.

The board has 12 output pins that can control various devices such as stepping motor drivers, Plasma Torch, Pump for coolant, spindle, 5 Input pins are provided for limit or home switches, feedbacks, Emergency switch.  All inputs has 470E for TTL Voltage input required driving the inputs.

Note: For 24V inputs replace R10, R12, R13, R15, and R16 with 2K2 Ohms.


  • Supply 7V to 36V DC output side of opt-coupler
  • 5V DC for PC side
  • 25 D SUB Male Connecter for PC LPT Port Interface
  • High Speed Opto-coupler s 6N137 on all outputs
  • PC817 Opto-coupler for Inputs and Output Controls
  • On Board USB Connector for Supply from PC or other source
  • All Outputs are buffered and optically isolated
  • All inputs are optically isolated
  • Screw Terminals for all outputs and inputs
  • On Board L317 Regulator for 5V DC
  • Heat sink for regulator
READ  Designing a mains frequency monitor


  • CN5, CN6: 5V DC Supply input for PC side of isolation
  • CN4: 7 to 36V DC Input for output side of opto-coupler
  • CN2: Optically isolated Outputs
  • CN3: Inputs

For more detail: Optically Isolated LPT Breakout Board for CNC & Routers

Current Project / Post can also be found using:

  • linux Optically Isolated LPT Breakout Board for CNC

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