Parallel Port Interface PCB rev 2

With what I learned from revision 1 of the parallel port interface PCB I designed the new version. The goals I wanted to achieve compared to revision 1 are:

  • Better protection of parallel port.
  • Input / Ouput selection for bidirectional ports.
  • Actual working relay up to 2 amps at 12v.
  • Smaller (3.2 x 1.6″).
  • More GND outputs.
  • Always on 5V output (VCC).

Features from Rev 1

  • Efficient Power supply (using switching power supply).
  • Easy connectors.
  • Reasonable priced components.
  • ESTOP relay shuts down 12 and 5v lines.
  • Integrated pull ups for input lines.

So the new revision does that I believe. I’ve ordered 10 PCBs from Seeedstudios. This means I’ll have a few left over. If anyone is interested in them let me know. I’ll have all the components as well.

The new schematic includes a 74hc245, a bidirectional buffer. The inputs have built in pull ups and protection resistors. And the relay switches both the 5v and 12v lines on and off.


Looking around on LaserPointerForums today I found this guys’ build he has a very nice looking Laser CNC made out of metal.

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