Building a Power Jack Switch For Your Sailplane

 

By Steve Greenfield 12/2002

 

What is a power jack and why would you want one? A good question. Simply put, the power jack replaces both the switch and the receiver battery charge jack in your airplane. No more having to deal with connecting and disconnecting wires sticking out of your plane in order to charge the internal battery. No more replacing the super cheap switches most RC radio sets provide.

The power jack is very unobtrusive (see Figure #1below). The power jack has a plug in place when you want to leave the power disconnected, or you want to charge the internal battery of your plane. When you remove the plug, you battery supplies power to your receiver. Very simple.

Some care is needed. This is a popular thing modelers do, but they often do it with substandard jacks. Sometimes even using stereo jacks. Stereo Jacks are not designed to deliver DC power ! If you are listening to your stereo and the jack fails, all you get is some crackle. If it fails in your plane, the result can be a disaster.

You must use high quality DC coaxial jacks designed for this purpose. I use and recommend the Switchcraft 712A power jack used with the Switchcraft 760 power plug. Both are available at many electronic supply houses, or online at http://www.mouser.com.

Currently I am using Hitec radios only, this works fine for those. Any others brands, try at your own risk. As with anything else, this requires care, and I cannot personally guarantee results. It does work consistently for me; I have them in every new plane I build.

Figure #1

 

Here is how we build one.......

Figure #2

Figure #3

Figure #4 The 712A standing on end

Figure #5 The wired jack

 

As you can see above, you need to solder the black wire from both the reciever pack plug, and the battery pack plug to terminal #1

You need to solder the red wire from the battery pack plug to terminal #2

You need to solder the red wire from the receiver pack plug to terminal #3

IMPORTANT: Use a low wattage soldering iron, and shrink wrap the solder joints.

In a thin wing like the Jazz, you must carefully bend each of the lugs 90 degrees outward to reduce total depth of jack.

 

Figure #6 Wiring the Plug

 

This one is easy, just solder the charger jack wires as shown.

 

 

Figure #7

There we go !! All ready to install in your plane. Makes a very tidy installation. Please let me know how it works for you.

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