Instructables

A USB Power Controled Plug Strip. With Isolation.

Featured

Step 3: Enough talking time to build.

I chose to mount all of the components in a standard electrical box, for low load situations the box itself is probably enough of a heatsink for the SSR. But I had an old processor heatsink that was pretty good fit. So it was added to the box behind where the SSR mounts. Don't forget to add some heatsink compound between the SSR and the box, and some between the box and the heatsink.

The cord for the Plugstrip is cut in half and run through the electrical box. The neutral (white wire) is spliced with a crimp terminal. The grounds (green wire) are spliced and connected to the metal chassis for safety. The hot wire (black) is connected through the SSR with crimp terminals. This concludes the line voltage wiring.

The +5V and Ground from the USB cable (pins1 and 4) are are connected to one end of the fuse block, and one TVSS The TVSS diodes are simply crimped into the connectors for the fuse blocks. Simple, fast, easy. Then two wires are run from the other end of the fuses (with another TVSS) to the control terminals of the SSR. Most SSR's will have one of the control terminals marked for the positive (+) lead. Make sure to get the polarity right.

Make sure to insulate the other two wires in the USB cable from each other and the metal case. If you do not you can short out the USB buss and cause all kinds of other problems.

This concludes the wiring.

I added a small piece of plastic (recycled blister packaging) to form a voltage barrier between the high and low voltage sides of the case, as extra insurance.

 
Remove these adsRemove these ads by Signing Up
cboy2us5 years ago
This provides isolation?!?!?!?!, first lightning strike, you will pay for.
nforge cboy2us4 years ago

Isolated ground can mean a few different things depending on who you ask.  But typically the requirements for an isolated ground are that it's wired directly back to an electrical panel, not relying on conduit or other metal items to link it back to a panel.  But when it's in a residential application, this is as good as an isolated ground, it would be a straight run back to a panel, and as long as the box is grounded it's as safe as you'll get.  http://www.mikeholt.com/technical.php?id=grounding/unformatted/ig1&type=u&title=Isolated%20Ground%20Reference%20One