Entries from November 2015 ↓

I Don’t Think

Those three words instantly disqualify the speaker from expecting any respect, credibility, or attention.

DC Power Distribution

This device is a plug-strip to provide power to devices requiring 12 volt DC power at up to 30 amps.

Such a plug-strip is available commercially but it is somewhat pricey at around $100. I had better things needing my $100 so I built my own plug-strip for about $20 worth of parts.

My plug-strip provides two groups of four 30 amp connectors per group. Each group is protected with a single in-line fuse. One group is powered from an old PS-30 power supply. The other group of four gets its power from a battery that is kept charged by a 100 watt solar cell.

The 8 connectors are held in a groove cut into a block of redwood. holes drilled through the wood block allow the wires to extend to the back of the wood block for termination.

The connectors are glued into the groove using epoxy. Epoxy is also used to glue a sheet of aluminum to the top of the wood block. The aluminum extends past the ends of the block and has holes drilled in the extensions to mount the plug-strip to the underside of a shelf.

Power comes into the block from behind through the in-line fuses. The wires are soldered to the mass terminations formed by the connections from the individual power connectors.

Make sure the connectors are working properly before being glued into the wood block. The silver plated tongue of the connector must be inserted far enough to engage the the metal leaf spring in the bottom of the connector housing. Otherwise the act of inserting the mating connector will push the tongue back into the housing an break the electrical contact.

Insulate all terminations with heat shrink or electrical tape. All interconnects need to be soldered.

I saw no need to fuse each plug-strip location individually but it could be done that way if you want. Just buy six more in-line fuses and holders.

Note that the fuses protect the battery and power supply. They are not designed to provide protection to devices plugged into the plug-strip.


Instead of gluing a mounting strip to the power strip, we used shoe goo to glue the strip to the top of a removable metal sheet that is used to protect the desk surface. This was far easier and simpler than trying to install the strip at the back of the underside of the shelf.

Power connections to the srip were made using two pin molex connectors. The connectors were keyed to ensure connections could not be reverse polarized and provision was made to ensure the power sources could not be interchanged. Solar/battery power could only be supplied to one set of four sockets and PS-30 power could only be supplied to the other set of four sockets.