I would like to light 4 LED in series(12V). It is easy to draw its power from SMPS. But i would like to lit it only when hard disk light is on. But its poweq will not come fr HD light. is there any electronics that will just send on/signals. The light should work simultanously. Please no use of photo diode. The circuit suggested must be simple. This mod will be a meanigful. Send the circuit dia.