DC/AC Power Distribution Panel

This is an entry in our current non-fiction writing contest  By DanW

Intro:

power panel 231x300 DC/AC Power Distribution Panel

Click on image for full sized view.

This article covers the second half of my Portable Solar Battery Charger & Power Distribution Panel project.  This is a detailed description of how to build a Multi-Voltage DC and (Inverter generated) AC Power Distribution Panel complete with a parts list, component functional descriptions, schematic, and photos. Although I tried to be concise, it still turned out to be rather lengthy!  After conferring with MD, we was decided it would be best to publish this as a 4 part series. Part 1, 2, and 3 will include the design details, schematic, and several photos of the Power Panel.  Part 4 will be the Construction Notes. So, thanks in advance for your patience ………. Hope you like my efforts!

A note of caution: When working with anything electrical you should always pay heed and follow all safety procedures to prevent harm to yourself or others. I suggest you do not attempt to build and/or use one of these units unless you have a good working knowledge of basic electricity.

This Power Distribution Panel turned out to be a bit more expensive than I expected.  But, flexibility comes with a price tag.  Before deciding to build this project I did some research to see what was already available.  I found several bench power supply units that produced a range of voltages …….. one voltage at a time ……. and of course they all required 120 vac input power. They were also in the $600 – $800+ price range and not designed with the versatility of this little Power Panel.  You may find that your version of this project is less expensive ………..  It could certainly be built for less.  But, if you scrimp on your design now it will be very difficult, if not impossible, for you to add to its features after the SHTF.  I know it will power the devices I currently have, but what if I had to replace one of them?  Even if I’m able to find a similar device …….. would a less complete Power Panel be able to meet its power requirements?

Hopefully I’ve given you all of the information you’ll need, without getting too technical, so you can make one of these for yourself.  The schematic, layout design, and photos should help to clarify all of this.

Background:

My goal was to design a compact, relatively portable power panel that will provide multiple voltages at the same time, generated by multiple electrical sources utilizing flexible connectivity for multiple load devices.  Whew!  That’s a mouthful ………. but it does kind of say it all in one sentence.

This Power Distribution Panel is designed to be used with a 12 vdc deep cycle battery as the primary power source.  In my case that’ll be a battery charged using my Portable Solar Charger.  I’ve made the design as flexible as possible for my own needs; but, since not everyone will need or want something with all the features I’ve put together, this design lends itself to be inherently flexible.  You can easily select which portions of the circuitry might suit your needs and build yours accordingly.

My earlier post http://www.thesurvivalistblog.net/power-for-communications-defense-and-entertainment/ outlines how I designed and built a hand-truck based Portable Solar Charger.  The design process for that unit was predicated on producing enough solar generated electricity to be able to charge a deep cycle battery.  I took into consideration the need for a battery of sufficient capacity to supply 12 vdc @ 5 amps/hour output for at least 18 hours. I arbitrarily selected 5 amps as the max total current draw (Ampere Load) to be placed on the battery based on the power requirements of my load devices.  It should be a rare instance if all of the devices were being used at the same time.  So, the factors determining the battery’s discharge rate was the total size of the ampere load (CB Base Station, Scanner, Radio, etc.) and the length of time the battery would need to be able to reliably supply that load (18 hours @5 amps).

Having resolved those issues, it was now time to address the Power Panel design and assembly.  I needed to take into consideration the various voltages required to power my equipment, the layout of the unit so as to provide for quick and easy connections, and the overall physical size and dimensions of the Power Panel.  An additional factor was the need for this Power Panel to be somewhat portable.  By “portable” I mean being able to set it up in a variety of locations if desired.  My radios, CB base station, scanners, and home perimeter defense system base unit, etc. all can be powered by 120 vac, 12, 9, or 6 vdc. Therefore, these are the voltages to be supplied by the Power Panel.  Armed with that list, plus a rough idea of how I wanted to physically connect the power cords from each device to my panel, I searched the internet for quick-connect power strips.  I wanted to find this component first as it would, to a great extent, determine the physical size of the panel as well as the final layout.  After a lot of online browsing I found the exact thing I was looking for ……… a power distribution unit made by Tenma.

The Tenma Units:

Manufactured by Tenma, these DC Power Distribution Multiple Outlet Panels are readily available from a variety of retailers.  I purchased three from MCM Electronics http://www.mcmelectronics.com/  as they had the best unit price plus free shipping. Once wired, each of these Multiple Power Output units would offer a different voltage: 12, 9, and 6 vdc respectively.  Referring to the schematic, you’ll see that the three Tenma units get their power from the 12 vdc buss. These units are divided into two sections: switched and un-switched. The un-switched pair (each with a 35 amp fuse) is rated at 35 amps total while the switched set of 6 pairs is rated at 15 amps total with one 15 amp fuse.  The only thing I did not like was the rather inconvenient location of the fuses: all three fuses are internal and not easily accessible.   A work-around solution to this issue is the addition of another fuse on each Tenma unit.  A panel mount style fuse holder with twist off cap holding a 10 amp AGC fuse will protect the switched DC outputs.  Theoretically, this 10 amp fuse will fail before the internal 15 amp fuse.  I drilled a hole in the right side of each Tenma unit to mount the new panel fuse holder.  Once the fuse holder is installed it must be wired into the circuit.  (Since the fuse is held in the fuse holder by spring action you should use a flexible type stranded wire rather than solid copper for these new connections.) To do this you will need to cut the existing solid copper wire from the small internal circuit board to the On/Off Switch.  Connect each end of this cut wire to the terminals on the new fuse holder and insert a fuse.  The fuse holders on the 9 and 6 vdc Tenma units are not actually needed since these two units are protected with front panel mounted 5 amp fuses on the positive output side of the respective voltage reducers.  However, I went ahead and installed fuse holders in these units for the simple reason of being able to use the 9 or 6 vdc Tenma units as replacements for the 12 vdc unit if it was ever needed.

Each Tenma unit comes with two Ammeters: One for the un-switched outputs and a second one for the switched outputs.  The output connections are banana type posts, used in pairs (+ and -) where your devices (radio, scanner, etc.) can be quickly and easily connected.  These “banana” type posts can also be unscrewed to expose a hole that will accommodate a bare wire.  Once the wire is in place you tighten the screw part down firmly.  This option eliminates the need to purchase the banana type plugs if you chose. There is also black Banana plug jack labeled “Ground” on each Tenma unit.  This ground terminal is connected to the Tenma case only and is isolated from the positive and negative Tenma DC outputs. If you connect this ground terminal to the AC ground then the metal front panel will be grounded. As I comment below, this may cause problems so I suggest you leave this ground terminal unused.

Voltage Reducers - Note also that there are two voltage reducers in use: 12vdc to 9 vdc and 12vdc to 6 vdc (see the parts list).  I found these Voltage Reducers online at http://www.powerstream.com  . Rated at 5 amps, they are each protected with a 5 amp fuse placed in the 12 vdc positive line feeding each voltage reducer.  Higher amperage and different values are also available.

Basic Power Panel Box Construction:

I addressed my desire to keep the AC and DC circuits separate by using a combination of metal and wood for my front panel design.  The metal section will be DC circuits while the wooden section has primarily AC circuits.  I did this for two reasons:

–          To provide electrical isolation between the 12 vdc and 120 vac componentsI don’t know the electrical integrity of the various components (primarily the voltage reducers) and it is possible that mixing in an AC ground with the DC components may cause interference or damage to some of these devices.  Keeping them somewhat insulated from each other reduces that possibility.

–          From an assembly standpoint it is easier to mount the various switches, meters, and other components to the thinner metal panel than it would be on a much thicker wooden panel.  My Construction Notes deal with issues of mounting components on the thicker wooden panel.

Your enclosure will be defined by your needs and imagination.  The size of the box frame and metal mounting plate will depend on your particular layout, number of components to be mounted, etc.  I decided to use a piece of light gauge aluminum for the front panel component mounting plate.  This plate slides into a slot cut into the inside of the wood frame and is held in place when the top piece of the box is attached with screws.  I used a wooden section (assembled with the box frame) for mounting the 10 Socket 120 vac Power Strip and associated switch, the 120 vac Meter, and the Inverter switch and fuse.  Red oak was used for the box as it is stable and strong.  Pre-fitting showed me that I needed to use a piece of 2” x 8” (3/4” x 7 ½”) cut down to a width of 6 ½” for the bottom of the box frame.  This was done so that the Inverter would fit properly. I cut a slot in the back bottom of the wooden front panel section where one side of the Inverter mounting plate will fit. The finished dimensions of the box are 24 3/8” x 22”. I used Philips head machine screws to assemble everything so it could all be taken apart easily with a manual screwdriver.

The layout for drilling and cutting rectangles in the metal and wood front panels is a critical aspect of producing a final product that is organized and neat.  I used a piece of light weight poster board to make a layout template (using the actual components) which I transferred to the front panels. Then it was a simple matter of making the cuts and drilling the holes using step drills (See Optional Parts List).  It’s much better to make your layout mistakes on paper ……. rather than on your actual panels.

To Be Continued: Part 2 will be published soon and continues with more information on design details and assembly of this Power Distribution Panel. A detailed parts list and component functional description is include in Part 3 with Construction notes in Part 4.

Prizes for this round (ends May 24 2014) in our non fiction writing contest include…

  1. First place winner will receive –  A $150 gift certificate for Hornady Ammo  courtesy of LuckyGunner, a Wonder Junior Deluxe grain mill courtesy of Kitchen Neads, a one year subscription to the Personal VPN service courtesy of unspyable and Three Survival Seed Vaults courtesy of LPC Survival.
  2. Second place winner will receive – Brand New, Sealed Case of Military MREs (Meal, Ready-To-Eat)  a $119 value courtesy of Campingsurvival.com and a Survival Puck  courtesy of Innovation Industries.
  3. Third place winner will receive – a copy of my book ”31 Days to Survival: A Complete Plan for Emergency Preparedness“ and “Dirt Cheap Survival Retreat” courtesy of TheSurvivalistBlog.net a copy of “The Survival Medicine Handbook” courtesy of www.doomandbloom.net and a copy Herbal Antivirals and Herbal Antibiotics .
my family survival

Comments

  1. Absolutely Cool. I am a Ham Operator and also have a CB base station. My radio “shack” in one of my bedrooms is a maze of componants and wiring. I have been looking for a better way to organize this better for a long time. I am looking forward to the rest of articles. Good work.
    I

  2. Jersey Drifter says:

    WOW…..good stuff. This has got me to thinking, I need to build one. Being a former Navy aviation electronics technician, former computer repair technician, and a former technical support technician, I like this kind of stuff. But I must stress ” former ” because it has been a long time since I worked in that kind of field.
    My skills are so rusty I need help changing a light bulb. But I am looking forward to reading the next parts in your series.

  3. JP in MT says:

    This is AWESOME! Just what I’ve been looking for. Along with the other parts, I think this will be my Summer Project!

    Thanks!

  4. Big Bear says:

    Hi all,
    Much more to come on this Power Panel. I tried to put the article together so it would be easy for those interested in something like this to decide what they wanted to build for their own use and to round up the parts. The parts list that will be published eventually (don’t know how MD plans to post the remaining information) has links so you can go on the web to check them out. The schematic will also be published along with one of the 4 parts of my article. I too was an ET during my 9 years in the USN and stayed in the electronics field after I got out. I started in electronics when everything was still vacuum tubes ………. transistors hadn’t made it into general use back then. Don’t hesitate to post your questions, or comments, and I’ll try to answer each one.

  5. DB Prepper says:

    I’m with JP, awesome project for the summer months…once my shed is rebuilt (got destroyed in our “mega quake” 5.1 last Friday)

  6. Okie in CO says:

    For All. Wal Mart has propane refills for $18 and get $10 gift card or $48 for tank and propane for $48 and get a $25 gift card. heck opf a deal

  7. riverrider says:

    very cool. i just use the harbor freight charge controller that comes in their solar kit as an out put. it has 3 thru 12 volt sockets.

    • Big Bear says:

      That controller is a nice little unit and I checked it out back when I was in the early stages of figuring out what I wanted. After reading your comment I went back and re-read the manual for that controller. The main reason I didn’t choose this unit is that it is severely limited to the amount of total wattage it can provide and doesn’t have a 9vdc output. It doesn’t provide more than 4 amps at 3, 6, or 12 vdc and, if I’m reading correctly, only one of those outputs may be used at a time. Is the inverter output 110vac? Couldn’t find a spec for it. The manual doesn’t give much information or specifics as is the case with many of these devices. But, if it works for you ………. then all’s good!

      • riverrider says:

        i have used more than one output, maybe i shouldn’t have tho. i won’t anymore, thanks! its strictly 12 or less output. i have a 3k hooked to my battery bank for 110v. what you are doing is fantastic. i just fear that some folks will be scared off solar by it, you know, “omg its too complicated.” i’m just a simple guy. even tho i worked on army electronics successfully, i never REALLY got comfortable with it. i’m more a visual guy. piston goes this way, makes cam turn that way, spark goes bang,lol. i can’t see resistors and diodes n such do their magic, so to me its just that- magic- and you are a magician, lol.

        • Big Bear says:

          No magician ………. just an old guy that enjoys building things. I think once the entire article (with the schematic and photos) is posted people will see how it’s not that hard to build. I have lots of time to play with this kind of stuff and enjoy woodworking as well so it was a challenge to me to put it all together. The best part was when I turned it all on and it worked the first time.

  8. RJArena says:

    I used to sell hundreds of the Harbor freight units, most went to Haiti, but some stayed local, I had one customer that had his whole shop set up to run on solar with his back-up deep cycle batteries, I think he had 6 or 8 sets of panels.
    The biggest complaint I ever received was breakage due to debris in wind storms, hard to avoid, since you can not control what the wind brings onto your property….

  9. DanW,
    In my earlier years before I could afford a lot of store bought equipment and I had better vision, I did a lot of projects like these, so it’s good to see some folks are still doing them, in what’s become more of an appliance operator world. One of the tools that I found and still find very handy to have in the toolbox is a set of tapered hand reamers which I find more versatile and a little less expensive than the step drill. You start by drilling a ¼” hole and then ream it out to the required size. Just another potential option for project builders.

    • Big Bear says:

      I looked into the hand reamers and believe it or not the step drills were cheaper. I have an old hand reamer (just one)but I also have old hands so I figured I’d splurge a bit and get the drill driven types. I always check out the tools when I’m out garage saleing .. never know what will pop up!

      • Big Bear,
        I understand about the old hands; but, there’s no good reason not to have the drills AND reamers. Can never have too many tools around.