inspired from metku mods i decided to make a circuit which will look like a knight-rider kit when hdd led lights up. and in the middle will be a big led which will light up when the power is on. so whole thing will look like this: the problem is the circuit i found runs at 12V but the hdd header gives 3 volts i need some kinda trigger circuit which will give out 12volts taken from molex the light circuit when hdd header gives pulses. to explain it better i made a schematic: looking forward to hearing from you MasterOfDisaster
You want an optoisolator, and I thought japala had one in his schematic? It does exactly what you describe, plus provides total electrical isolation between your circuit and the mobo. Edit: ok, I see you're not building his circuit. USe an optoisolator: Pin 1 and 2 go to your HDD header, pin 3 no connection, pin 4 to ground, pin 5 to the - of your circuit's power supply, your circuit's power supply to +12 off the PSU, and pin 6 no connection. 4N25 is a part number for a typical optoisolator, Maplin code AY44.
linear sorry but being a total newbie to electronics i would like to ask 1 more thing. i made another diagram: did i get it right? probably not if not could you please draw sthg. i know i'm being a pain in the arse but pleeze help me
Close: Also note that your use of red and black on pins one and two kind of implies a polarity, which I think you have reversed. Pins 1 and 2 are connected to an LED inside the package, so it's polarity needs to be right for this to work. Also note my changes to the pin numbers, in red.
