Greetings!
This is posted on 4/01/14, but is
not an April Fool's joke. See the Unicomp SSK thread if you are looking for humor.
This
is a making stuff together thread that answers the question:
How do I make a string of LEDs light up when my hard drive activity LED flashes?If you have never asked that question, then this may not be interesting to you. I
have asked that question, and this week I took the effort to make a circuit that does exactly that. When the HDD activity LED flashes, this circuit makes a 12v string of LEDs flash in parallel. It uses a separate 12 volt input and a transistor to make the magic happen.
Here is the circuit diagram:
HDD LED Circuit by samwisekoi 2014Here is how it looks on a one-inch square PCB or prototyping board:
HDD LED PCB by samwisekoi 2014This is a tiny PCB, with only a few inexpensive parts, including a fifty-cent NPN transistor. It will work if your motherboard pulses the HDD
ground (as they normally do) or if it pulses the HDD 5v (positive) line. The optional LED in the circuit is flashed by the motherboard as a replacement for the normal case LED. You could wire D1 to your case LED, or place a 5mm LED directly on the little PCB to show that the switched circuit was replicating the normal HDD activity LED. Or you could leave it off entirely.
I am using this to illuminate the interior of a small NAS box when the array is used, but you could use it for any purpose. In fact, you could wire it to pretty much any 5v circuit to flash an LED strip in parallel.
I designed a 1x1" mini circuit board, and if a few people are interested I could have some prototypes made. They would be about $5 each in green or $10 each in black. Of course, they'd be less than a buck if I have a whole bunch made, but really, how many of these can one man use in a lifetime?
In the meantime, I am making my prototype on a scrap of breadboard. I'll post some pictures and a Mouser parts list, probably tomorrow.
If anyone besides me is interested in having some actual PCBs made for this circuit, reply in this thread. Otherwise it shall remain here for posterity and future searchers who want to make some LEDs flash when their hard drive activity LED flashes.
Enjoy!
- Ron | samwisekoi