LED Amplifier
I recently built a new PC and noticed after I was done that the
hard disk light was almost impossible to see. I tried different
LED's that were more efficient and even thought about modifying the
motherboard. But, I decided to avoid that risk and make things
interesting by designing this circuit instead.
Since I didn't know how the LED was being driven on the
motherboard, I decided to use an optoisolator (ISO1) to act as an
interface. This provides electrical isolation as well as an
equivalent load. Since the current going to LED was already pretty
weak, I chose a device with a photo-darlington transistor
amplifier. This provides a minimum current amplification of 15 or a
Current Transfer Ratio of 1500%.
I had some Disk Drive power Y-connectors and I cut one of those
up to use as the power jack, J1. The +12 signal will be a yellow
wire and ground will be one of the black wires.
R1 was chosen to provide about 20mA of current through either a
blue or white LED. I used a Panasonic LNG992CFBW blue LED and it
looks pretty cool.
To connect the circuit, turn off your PC and remove the cover.
Locate and remove the HD LED connector from your motherboard (MOBO)
and connect it to the two pin header, JP1. Plug J3 onto MOBO in
place of the original LED connector. Locate an unused HD power plug
and connect it to J1. If one is not available, you may have to
purchase and install a Y-adapter.
Remove the original LED from the socket on the front of your
computer and replace it with your new, exotic LED. Apply power to
the PC and observe the HD LED. If it does not flash with HD
activity, you may have to rotate J9 or D1 to get the polarity
correct.
Once operation has been verified, button your computer back up
and invite your friends over to see your new exotic machine. Trust
me, once this modification has been completed you will know when
your hard disk is being utilized.