The following is a brief explanation of how I have my Direcway modem(s) operating by using a single 12 volt DC power source.

As some can and will attest, that living 'off the grid' has its pros and cons.
One of the biggest concerns is battery capacity consumption by the inverter and the equipment the inverter services.

When you power on the computer and its associated equipment and the AC adapter for the Direcway modem(s) you will begin the process of draining your batteries at a fairly rapid pace.

If we can eliminate a portion of the drain, then we have reduced the consumption of the battery capacity. Therefore, we can use that extra battery power to stay online for a longer period time.

The very first item to be considered is the availability of the 12volt to 24volt DC converter. The converter is used to convert the 12volt battery supply into the 19.55 volts needed by the modem(s).

This is the heart of the project, but the listed store bought converter is not the only thing that will work. My idea is to purchase something that has been tested and built by professionals. The converter can be home-brew if you want to do that.

What you will need is 19.55 DC volts with an amperage rating of at least 4 amps. I can furnish the links to the schematics for those that want to build their own converter.

Gather the parts listed in the parts list and assemble the circuit for the low voltage side of the system. Follow the schematic for the LM317. You will want to replace R2 with a 1k trimmer because you can adjust the output to 6.55 volts. That matches the adapter output more closely than the fixed voltage of 6volts. You will need to install the heat sink on the LM317.

*NOTE* Change the 1meg trimmer above, to a 1k trimmer.

Keep you your circuit wiring neat and tight on the regulator board. You need some space to attach the 12to24volt converter.

Once the LM317 circuit is built and tested for output you can now begin the process of wiring the 8 pin DIN cable that will supply the twin voltages to the modem(s).

There are only five wires of the cable that will be used. Two wires will connect to the output of the converter and two wires will connect to the adjustable voltage regulator (LM317) and the last wire will be ground.

I simply cut one end from the DIN cable. The bare end was stripped of the insulation (about four inches) and the wire separated. I used the Red, Yellow, and Orange wires to supply the voltage and ground circuit for the Direcway 4K modems.

The Black and Tan wires are used in addition to the above for the Direcway 6K modem.

You now have the voltage regulator assembled and tested. You have the 8 pin DIN cable prepared and ready to attach to the voltage regulator and the 12to24 volt converter. At this time you want to attach the converter to the regulator board.

You will notice that the converter has a four position connection block for connecting 'input' and 'output' wires. Position the converter on the regulator board with the 'blue' capacitors in the up position and the connection block facing to the left side of the regulator board. In this area of the regulator board you will want to lay a thick bed of hot glue in which to glue the converter to the regulator board. You may also want to bed the 'black' capacitors with hot glue to add stability to your project.

Above: Converter detail

With these two pieces firmly attached to each other it is time to do the wiring for the 8 pin DIN plug.

The ORANGE wire on pin #4 is connected to the output of the LM317.
For 6K application connect the Black wire (pin #7) to this same point.
The RED wire on pin #7 is connected to the VYSTUP terminal on the converter's connection block.
For 6K application connect the Tan wire to this same point.
The YELLOW wire on pin #8 is connected to one of the MINUS terminals on the converter's connection block.

Now it is time to do the wiring for the 12to24volt converter.

The remaining ground wires (input ground to the LM317, input ground from 12volt supply) are common so they can be connected to the converter's other MINUS terminal.

The 12volt positive wire connects to the VSTUP terminal of the converter's connection block.

Be sure and install the 4amp fuse in a fuse holder of your choice. This fuse protects the completed project, including the modem(s).

Adjust the output voltage from the 12to24 volt converter to 19.55 volts. Check the output voltage from the regulator for 6.55 volts.

Once you determine the location or enclosure for the completed package, a small muffin fan can be installed. You can use the converter's VYSTUP and VSTUP connections to tap power for the fan.

With a DVM check to ensure that you have the correct voltages on the correct pins of the DIN plug. You should have 19.55 volts between pin #8 (ground) and pins #1&7. You should have 6.55 volts between pin #8 (ground) and pins #4&6.

If everything is to your satisfaction then it is time for the SMOKE test.
Remove power to the AC adapter and remove the AC adapter's DIN plug from your modem. Insert the newly wired DIN plug into the modem, apply your supply voltage and wait for the modem(s) to start their test.
The heat sink will be warm on the LM317 regulator and the 12to24 volt converter. This is a normal condition and indicates that each of the components are working. If the heat sinks are extremely hot to the touch, remove power and recheck your work.

Start your computer, open your favorite browser and surf the Internet the 12volt way.

Miscellaneous Stuff; wire, solder, fuse holders, hot glue gun. Project box if well ventilated.

You will need to contact jaro@surfside.net to check on availability of the 12to24volt converter.

The Housekeeping

If you have concerns about this project have your work and/or the project checked by a professional.

Constructive criticism is welcome.

Questions can be e-mailed to me at sundancer87@runbox.com.

Enjoy the project and share the knowledge.

If you plan on making money from my experiment please send me a percentage of your earnings.

The Disclaimer

I am not responsible for damage to your modem(s), to your Computer or to your house or dog.