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The labjack u3 hv is the interface between my home and my custom built automation system. Anytime I need to reboot the pc, which is very rare, the labjack u3 hv power supply is cycled via the usb port.

For utmost reliability I need a separate 5v supply to my labjack. This is how I achieved it.

Step 1: Putting the House Into a Safe Mode.

Before I can shut down the pc to perform the modification, I have to do certain things to ensure the home automation system end devices don't go crazy.

First I switch the home power from solar to utility. Next I manually turn on the inverter that will power my living room air conditioner. Finally I turn off the breaker that powers the relay bank that controls door food/water, home loads inverter and a couple other devices.

Now I can safely power down the home automation pc.

Step 2: Modifying the Usb Cable.

Here I unplugged the usb cable from the labjack and used my utility knife to carefully cut away the jacket. Once the wires were exposed I cut the red wire that delivers 5v from the usb port. I put liquid tape on either end of the wire to avoid reconnecting.

Step 3: The New 5v.

The M4 atx power supply gives continuous power even if the pc is rebooted. From a previously established power supply terminal block, I ran a wire from the 5v terminal to a Vs terminal on the labjack u3 hv. This new 5v supply wire has a 3amp inline fuse.

Step 4: Completion.

I plugged in the modified usb cable into the labjack u3 hv and turned back on the automation pc. The power on leds were lit and the system fully operational again!

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Bio: As of April 2017 I have decided to no longer post on instructables. The fact that several of my published works have been removed without ... More »
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