I apologize for an off topic, but as touched upon a subject WatchDOG, Board Made to himself of "Digispark Kickstarter Mini USB Development" (https://www.electroschematics.com/12102/learn-to-use-attiny85-usb-mini-development-board/), Ebay 2$. Created a small code which tracks for activity of HDD LED, in case of long absence of a signal reboots system. In operation it is connected directly to "front panel connector" on matherboard, without use to a relay. USB using only for loading of a code.