Last updated: 12 August 2006
Subject:	An Adapter to power an AirCable
Sent:	Thursday, August 10, 2006 23:48:47
From:	Clay Jones (
I have had my ETX 125 PE UHTC for about 2 months now, and being the
gadget geek guy that I am, I couldn't resist the idea of controlling my
telescope wirelessly using my Treo 650.

So I poured through the web sites and forums looking for ways and means
to do this, but I was a little suprised at the suggestions for powering
the AirCable.  Usualy it involed a pack of batteries velcroed to the
adapter with spares laying around in case they were needed.  "BUT THERE
IS 12 VOLTS JUST 1/2 INCH AWAY" my brain screamed.

So I looked up the pinouts from the ETX, Autostar, an AirCable.  Then I
rummaged through my computer junk drawer (OK, it's 3 massive filing
cabinets) and put together an adapter and cables that would allow me to
power the AirCable from the same 12 volts powering the Autostar.  Or in
other words, if the telescope has power, so does my AirCable.

I used the pinouts listed on as well as verifying
power and ground with a Volt Ohm Meter (a Fluke because I work for them)
before I cut or spliced anythingl. And I especially metered all cables
and connectors working my way from the telescope to the ETX and out
before I ever plugged anything in and possibly blew something up.

I took an Ethernet Cable Connector to tap into the 12 volts to the
Autostar, and soldered a small wire connecting a telephone cable
connector.  One thing to note is that Ethernet Cables and Connectors do
not have twists in them like Telephone Cables and Connectors.  You have
to be very careful to twist or not twist to get the righ pins together. 
Especially sine the Autostar puts Ground and 12V on the outside pins. 
If you get cables wrong, you'd apply -12V to the autostar and possibly
fry it.

Likewise, the Autostar RS232 shows pin 3 as being unused when in fact it
is also connected to the ground.  So if you don't cut the wire in the
telephone connector, you would short 12V to ground and possibly burn up
some wires (probably the small wire we're adding, but still it's risky).

My favorite thing about this little adapter is that it requires no
changes to the Telescope, Autostar, AirCable, or the Autostar cable.  It
just plugs in and can easily be removed or even loaned to a friend
without having to make any special changes.

I have provided 2 labeled photos and a schematic that I hope will give a
good idea of what I did.

You will need:
1 - Ethernet Cable Connector
2 - 8 pin RJ45 connectors (or more if you're like me and screw up sometimes)
1 - 6" Cat 5 cable
1 - Old phone handset coiled cord with the small ends still on
2 - RJ11 (4 wire) connectors (or more for mistakes)
1 - Telephone Connector Crimp tool
1 - Female DB9 connector or adapter
1 - 2" length of small thin wire
1 - Soldering iron with a very fine tip & solder & flux

I've used this setup for several weeks now and it works very well.  I
use Astromist on a Treo 650 to control the ETX.  It took just a little
while to get used to the constant connect/disconnect that goes on.  I
guess I thought it would always stay connected, but it's actually better
that it drops off after each command so I can power off my Treo while I
look through the scope.

Clay Jones
Colorado Springs




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