Making a battery pack adaptor for the M1 HMD

Making a battery pack adaptor for the Liquid Image M1 HMD

The following is a How-To detailing the materials and steps I used to make a quick and simple adaptor for hooking a Radio Shack R/C car battery pack to my M1 HMD. I use the M1 HMD in my Gargoyle wearable computer project. There's nothing much to it, really, but the end result is pretty usefull if you want to keep your HMD power source separate from your wearable's battery pack.

Parts List:

1 Radio Shack 7.2VDC NiCd "Hi-Capacity Turbo Racing Battery Pack" - RS catalog #23-330
1 pack of Radio Shack Coaxial DC Power Plugs (5.5mm O.D., 2.1mm I.D) - RS catalog #274-1569A
1 Radio Shack 7.2V Battery Charger - RS catalog #23-241
1 Tamiya 7.2V Connector Set - Can be found in most hobby shops that deal with R/C cars.
Soldering Iron, Electrical Tape.

Some Assembly Required...

Here are the parts we are going to work with. From left to right: Female connector from Tamiya connector set, electrical tape, battery charger, coaxial plug, and 7.2V battery pack.

Strip a bit of insulation off the ends of the connector set wires and slide coaxial plug housing over wires BEFORE you begin soldering. It may be necessary to widen the housing opening with a knife to allow the two wires to go through it.

Solder the Positive (red) wire to the inner tip, and the Negative (black) wire to the outer tip contacts of the coaxial plug. This can be tricky with large AWG wires and a small plug. Be sure that the two arent touching, and wrap some electrical tape around each after soldering to insure that they are insulated from each other. Tweezers come in handy for doing this. Slide the housing down over the wires and screw onto the plug body. In this picture, I wrapped some electrical tape around the plug housing and the wires to form a strain-relief jacket.

Here's the finished product in a operational configuration. The plug arrangment is simple and effective, and best of all, it WORKS! The battery pack is easily unplugged for recharging, as shown by the picture below.

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