AUTOSTAR INFORMATION Last updated: 15 February 2005

Autostar powered from USB port

Sent:	Tuesday, February 15, 2005 03:53:30
From:	Martin Larsen (martinlarsen@bigfoot.com)
After having bought an ETX-90 a few weeks ago, I made myself a serial
connection cable using information on Weasner's site. I soon discovered
the need for powering the Autostar without setting up the mount. Again I
found lots of useful info on the site, and I made a connection box by
simply mounting a DC female connector in an Ethernet (RJ 45) wall box as
seen on picture 1. That made it easy to power the Autostar handbox from
any 12 V DC power source.

Then I got an idea! I already used a cheap USB lamp for lighting up the
notebook's keyboard in the dark (tip: remove the glass and put some red
cellophane inside - or just wrap it around the lamp), and if the USB
port could power the quite bright lamp, why shouldn't it be able to
power the Autostar? Of course, the USB only supplies 5 V, but as seen on
this page http://www.weasner.com/etx/autostar/as_power2.html Autostar
runs happily on 5 V. And this page
http://www.weasner.com/etx/autostar/as_power2.html states that Autostar
draws less than 100 mA, whereas the USB specs allow for 500 mA drawn
from the port, so it seemed quite plausible.

I then took a spare USB cable, cut one end and mounted a DC plug
instead. Eureka! With the USB plug connected to the PC and the DC plug
in my homemade connector box, I was able to control and update the
Autostar without an external power source. The arrangement (without the
notebook) is seen on picture 2.


 



Inside a USB cable the power lines are red and black (for plus and
minus) so it's really simple to make the cable. Just cut off the other
two wires as you don't need them.

NOTE: The 500 mA allowed on the USB port is shared among all your USB
equipment. So if you use a really bright USB lamp, and a USB mouse and
.... you name it .... you *might* run into trouble! It works great for
me, though :-)

Martin Larsen

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