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.