SJ Instructions
Switch-Jack
Power
Switch / Charging Jack for RC sailplanes
The Switch-Jack is
designed for all model sailplane applications. Its maximum current
rating is a conservative 5 amperes at 12vdc. This is a continuous carry load rating. It is
more than sufficient for six servos in our typical 3 meter thermal duration sailplane, or
slope racer. The jack can handle the rough and tumble environment of model sailplanes with
ease. Total jack weight is 5.0 grams! Enjoy!
·
Jack with 0.016” washer, panel nut
·
One plug with red plastic handle
·
12” x ¼” red ribbon
·
1/8” thick, lite-ply mounting plate with
19/32” pre-drilled hole
·
3/4”L x 0.5”W 3M® polyolefin
heat shrink tubing
·
1.125”L x 0.125”W 3M® polyolefin
heat shrink tubing
·
Three AMP® slide on terminal connectors
·
This 2 page instruction sheet
·
Schematic and assembly 2 page diagram sheet
·
(Optional) Connectors soldered and heat-shrinked to
plug and jack.
Installation into fuselage:
The
Switch-Jack can be installed in any fuselage
with a wall thickness up to 0.125”. If you are not concerned with flush mounting the
jack, then just create a clean hole in the fuselage that is 5/16” diameter, and
insert the threaded jack bushing though the hole, fastening it with the included panel nut
and thin washer. A lock washer or Loctite® can be used to secure the nut more
permanently. Before drilling the hole, decide what side of the fuselage will be best for
the installation of the Switch-Jack. I’m right handed, and prefer the ribbon on the
left side of the fuse, so I will see it if I’m launching with receiver power off.
Flush
mounting the Switch-Jacks: A 1/8” plywood
mounting plate with a 9/32” diameter hole is included in your Switch-Jack kit. Cut or
sand the mounting plate to size to fit your installation. Allow approx. ¼” of plywood to remain all around the jack
hole for gluing. You may glue the mounting plate to the inside of the fuselage, screw it
on, or both. Sand to shape the surface of the plate that will attach to the fuselage so it
matches the curvature of the fuselage wall, if there is any. To prepare the inside of a
fiberglass fuselage for gluing, J.P. suggested these steps: clean the area with alcohol
several times to ensure a clean, chemical free surface. Then sand the surface so that
there is no shine left. Clean once more with alcohol, then use Goop® or 5
minute epoxy to attach the mounting plate to the FG fuselage. You may use epoxy,
professional wood glue such as Titebond®, or a good quality medium CA to
attach the plate to a wooden fuselage. Once
the plate is installed, carefully drill or cut away material from the fuselage for the
jack hole. Start small and work up to 5/16” diameter. A drill press is helpful here.
Use pliers to carefully screw the jack into the plate, keeping it perpendicular until the
threads grab. Protect the jack with electrical or wing tape when using pliers. Hold the
jack by the metal collar band around the middle of the jack. Do not hold the jack by the
plastic housing or terminals. The rim of the jack opening must be flush with the outer
surface of the fuselage to ensure proper switch action. Unscrew and remove the jack for
electrical connections, etc.
For
final flush-mount installation, screw the jack assembly with connected wiring harness into
the wood. The bushing is pretty tight in the plywood, and additional backing panel nut or
loctite is not necessary.
In
a thicker wooden fuselage up to 0.125” thick, install the jack directly into the
fuselage wall. Carefully drill the required 9/32” hole in the fuselage by starting
with a small bit like 1/8” and working your way up to 9/32” in small increments.
Hold the fuselage securely and use a drill press at high speed if available. If fuselage
is balsa, the threads can be hardened with CA if desired, but this is usually not
necessary on 1/8” thick, hard balsa. A backing nut on the inside of the fuselage is
used to lock the jack in the threads. The outer lip of the plug hole on the jack MUST be
flush to the outer surface of the fuselage. The base of the plug must make contact with
this lip to ensure operation of the switch.
Electrical connections:
Excessive
soldering heat will anneal the spring contact that holds the switch closed, relieving the
spring tension against the shunt contact and breaking the power circuit. Use a 15 watt
electronics soldering iron with a needle tip. The soldering specs of the jack are: 485 degrees Farenheit for only 5-7 seconds.
Hold the soldering iron tip to the jack terminal for only 5 seconds at a time. If you fail to make a joint in that time, let the jack terminal cool before you try again. Use a good quality electronics solder with rosin core. 1/32” thickness is perfect for the SJ but 1/16” thickness will work too. The terminals on the jack are marked with red ink. ONE DOT is the battery and receiver positive terminal, TWO DOTS is the battery negative terminal, and THREE DOTS is the receiver negative terminal. Refer to the schematic diagrams for circuit details. Production versions of this jack were marked with dots before delivery, making the connections easier. You may want to mark the terminals yourself before soldering to make it easier. Code is shown on the schematic diagram.
At one time we used Hobbico 6” servo extensions for the jack’s wiring harnesses. We then switched to Maxx Products gold plated connectors for the superior reliability and quality. Heavy and light guage wires are available. We always used the heavy guage. The following instructions refer to the use of a Hobbico Servo extension. In Hobbico speak, the big end is male (with the pins showing), while the smaller plastic connector is female (because it has hole that accept the pins). Maxx Products terminology is the reverse, they think the small plastic plug (male) is inserted into the large plastic connector (female) and they disregard the metal pins. Beware when you are ordering from Maxx Products. See parts list for the order numbers.
Cut
the extension 2” from the battery connector end (big connector) and leave 4” for
the receiver connection. Remove the signal wire from the receiver end and cut it off of
the battery connector. Before soldering, separate the positive and negative conductors of
the battery wire and receiver wire about 1” from the ends. Strip ¼” of
insulation off of the ends of the leads. Twist the battery and receiver positive
conductors together. Twist the battery negative and receiver negative conductor strands
separately. Pre-tin the copper leads. Trim the leads to 1/8” length. Put a small blob
of solder onto each terminal on the jack. Slip a 3/8” long piece of 1/8”
diameter heat shrink tubing onto each lead. Hold the positive lead of the harness against
the proper jack terminal (the middle terminal, with ONE DOT) and apply the soldering iron to heat up
the blob on the terminal. The lead and terminal will swim in the molten blob of solder and
you will have a nice joint with minimal heat. Repeat for the two negative leads. When you
are finished soldering, slide the connectors onto the jack (with the loops facing
outward!!) and shrink the heat shrink tubing onto the terminals with a heat gun. Heat
shrink the 1/2” heat shrink tubing around the plastic housing portion of the jack to
further protect the switch internals (optional).
Caution!! Soldering
irons and heat guns are extremely dangerous! They can destroy your parts and cause serious
injury. Please be very careful with these tools. Ask an experienced modeler or a parent
for help if you need it.
We
use a servo pigtail for the plug connection. Trim the pigtail to 2-3” length. Strip,
twist and tin the leads, then trim to 1/8” length. A small piece of heat shrink will
hold the conductors together if they separate completely when stripping. Connect the
positive lead to the the short plug terminal using the same “pre-tinned lead”
and “solder blob on the terminal” technique described previously for the jack
terminals. Connect the negative lead to the tall plug terminal in the same way.
Tie
the red ribbon around the tall lead of the unused plug, and use a micro drop of thin CA to
lock it. Don’t skip the ribbon, you will regret it when you are looking through the
grass for a $5 plug and those batteries are wasting away! Carefully crimp the two metal
fingers around the ribbon and wires to provide strain relief.
Connect
your charger to the plug. Insert the plug into the jack. Connect your Switch-Jack to the receiver and battery and plug
the servos in. The charging light should come on indicating proper charging connections
and polarity. Turn on your transmitter, then pull out the plug. Hopefully you won’t
see any sparks fly or your street lights dim - Haha! Your servos should come alive and
wiggle to tell you how happy they are with the new Switch-Jack
in place. If not, check your connections against the schematic for errors. Please call us
for assistance if you have any questions. Install the jack assembly into your plane,
charge your batteries and GO FLY!
Other Notes
Dirt
is the only achilles heel of the Switch-Jack
since it does not have wiped contacts like sliding switches do. Protect it from sawdust in
the shop, and dirt on the field.