Custom 12v HDD and power Lights for PCs - Part 3

Finished the circuit redesign, not too many changes mainly just added a second opti-coupler to make the motherboards happy.  Only problem now is that I have to solder 4 to cover all the PC LEDs

Connection from MB to Arduino

This may look overcomplicated, and may well be, just to light some LEDs.  So here is the thought process...
  1. Need to connect to motherboard LED lines, which expect an LED.  After prototyping I am using an opti-coupler - which is an LED :)
  2. Need to drive the case LED and the Arduino input, which are powered from different power supplies.
    1. Case from MB power supply
    2. Arduino powered by separate 12v power supply.
  3. Use transistors to drive case LED , 2 are required to invert the output from the opti-coupler - i.e. NOT gate.
  4. Use a second opti-coupler to connect the circuit to the Arduino
Hopefully that makes sense, any improvement suggestions let me know.


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