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ZL3AI > APRDIG 13.12.06 23:21l 240 Lines 9535 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 30 #9, 2/2
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From: ZL3AI@ZL2BAU.#79.NZL.OC
To : APRDIG@WW
Message: 9
Date: Sat, 09 Dec 2006 23:38:20 -0500
From: Tad Burnett <tburnett_at_vermontel.net>
Subject: Re: [aprssig] backup pwr systems
The secret is to not let the battery voltage go above 14.2 volts...
13.8 will not fully charge a battery so you do need to charge up to 14.2...
I found that I could do this with an old unregulated charger with
110 volt light bulbs wired is series with the 110 v primary of the
charger...
socket the bulbs so you can easily change them to find the right ones
to match your average load.. Use lamp sockets with a built in switch and
you can can switch them in and out if you are doing extra TX for a while...
You need a meter that you can easily see 1/10 th volt in the area of 13.8
to 14.2....
You can do that with a 1 mil amp meter and a 12 volt zener and some
resistance in series across the battery and then calibrate the face with a
good digital....
I ran a BBS with an old lap top with no internal battery in northern Vermont
where the power dropped out quit often and the battery lasted for years and
was always charge well enough to keep the laptop and radio going for about
10 hours before I had to jumper it to the car for a while to charge it
back up...
I don't know that I ever saved any life or anything at all but it is kind
of fun to have a packet station running just to see who else is still
running too...
Tad N1QAG
------------------------------
Message: 10
Date: Sat, 9 Dec 2006 22:02:41 -0700
From: Joel Maslak <jmaslak-aprs_at_antelope.net>
Subject: Re: [aprssig] backup pwr systems
On Dec 9, 2006, at 9:38 PM, Tad Burnett wrote:
>The secret is to not let the battery voltage go above 14.2 volts...
>13.8 will not fully charge a battery so you do need to charge up to
>14.2...
Exactly.
I might add that every automobile I've worked on has a charger
(alternator/generator) continuously running, connected to the battery with
no diodes, electronic switches, complex charging circuits, etc. They do use
a relatively simple voltage regulator to control the field current, which
in turn keeps the stator voltage where it needs to be (also reducing the
need for the regulator to handle high voltages, since it only has to
regulate the relatively small current field, not the high current stator
current). In effect, this means there is a steady voltage power supply in
an automobile, wired IN PARALLEL with a battery.
Long road trips don't hurt car batteries at all. And it's not unusual to
get 5 or more years out of a car battery even when environmentals are poor
for the battery (hot and cold temperatures).
If you play around with some electrical theory and find out the power
supply voltage and battery voltage are the exact same, you'll find there is
no current in a circuit with a power supply and battery wired in parallel.
That said, it's good to not charge batteries too quickly.
(nor do I recommend using a car battery - they don't do deep discharge
well)
So...in essence, you don't need a good charger at all. You need a power
supply that never supplies too much voltage. A properly sized diode and
resistor in parallel on the positive lead of the battery will manage this
quite well (diode to let the battery discharge at full current, and
resistor to ensure that you never are charging too quickly). Don't forget
fuses - your power supply's internal fuse won't keep your house from
burning down when the rig's power cable shorts out - you need a fuse on the
battery's positive lead rated for maximum load of everything hooked up, and
a fuse on every wire in the system that can't carry the maximum load of the
previously mentioned fuse (for instance, if you have a 12 gauge wire going
to your TNC, you probably don't want your 50 amp fuse on your battery to
allow 50 amps through that 12 gauge wire - and even 12 gauge wires can
start a fire!).
------------------------------
Message: 11
Date: Sun, 10 Dec 2006 05:18:27 -0500
From: Drew Baxter <droobie_at_maine.rr.com>
Subject: RE: [aprssig] House Temperature Probing
Good things to know, thanks for the info. I went out to the site tonight
and it looks like I can actually get into the APRS system from there, so
it's a good sign.
The Opentracker definitely looks well thought-out, keep up the good work.
--Droo, K1XVM
At 02:50 PM 12/9/2006, Scott Miller wrote:
>It self-heats only if you're putting a significant load on the regulator.
>You can also remote the sensor pretty easily. Or you can load the Dallas
>1-wire weather firmware and connect a DS18S20 sensor. I've got one of those
>in the garage - it runs about 20 feet from the tracker to my freezer to make
>sure the defrost heater hasn't broken again. It's more accurate than the
>on-board sensor and doesn't need any calibration. It also isn't affected by
>voltage drop on a long cable since it's a digital sensor - it generally
>either works or doesn't, with no degradation in accuracy.
>
>If you load the weather firmware with no external sensor connected, it'll
>just report the on-board temperature in APRS weather format. That lets you
>get graphs on Findu. If you do have an external sensor connected, you'll
>still get the on-board temperature in the status text. Check out
>wx.findu.com/n1vg-3 for an example.
>
>N1VG-3>APOT01:>Livin' in the fridge! 14.2V 23C
>N1VG-3>APOT01:!3457.54N/12025.44W_.../...g...t-12OD1w
>
>The board itself is at 23 degrees C, and the freezer is at -12 F. The
>status text always reports in C, so if you want F from the on-board sensor
>you've got to run it in weather mode. On the Tracker2 it's selectable.
>
>As for calibration of the on-board sensor, it has a very linear response so
>you only need a single-point calibration. Just check the real temperature,
>see what the sensor reports, and enter the difference in the temp adjust
>field.
>
>Scott
>N1VG
------------------------------
Message: 12
Date: Sun, 10 Dec 2006 05:51:38 -0800 (PST)
From: M J <mjandthegang_at_yahoo.com>
Subject: [aprssig] Receive Only APRS
Hello,
Is it possible to be a receive-only APRS participant? All I want to do is
to decode what I can hear on my scanner and see it on my computer directly.
I'm interested in a hardware device to do the decode if possible. IGWPE
(did I spell that right?) doesn't interest me. Any opinions about choices
available?
MJ
------------------------------
Message: 13
Date: Sun, 10 Dec 2006 10:01:58 -0500
From: "A.J. Farmer (AJ3U)" <farmer.aj_at_gmail.com>
Subject: Re: [aprssig] backup pwr systems
On 12/10/06, Joel Maslak <jmaslak-aprs_at_antelope.net> wrote:
>That said, it's good to not charge batteries too quickly.
>
>(nor do I recommend using a car battery - they don't do deep
>discharge well)
Batteries can be charged quickly, if done properly.
A car is designed to run with a functioning alternator all the time. If the
alternator fails, the battery will not last long. The battery's main
function is there to power the starter to start the car. In our
application, we want to use a deep cycle battery that picks up the load
when the main power supply fails. The battery needs to permit a deep
discharge and long runtime, and therefore requires a charger which can
supply a large charge current to bring it back in a reasonable time once
the power returns.
You are right, the electrical theory is the same, however the tools used
and goals involved are much different.
--
A.J. Farmer, AJ3U
http://www.aj3u.com
------------------------------
Message: 14
Date: Sun, 10 Dec 2006 11:08:39 -0500
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: RE: [aprssig] Receive Only APRS
Any APRS software and any TNC can be used for Receive-only APRS.
Bob
------------------------------
Message: 15
Date: Sun, 10 Dec 2006 08:37:49 -0600
From: Jason Winningham <jdw_at_eng.uah.edu>
Subject: Re: [aprssig] Receive Only APRS
On Dec 10, 2006, at 7:51 AM, M J wrote:
>Any opinions about choices available?
Once choice is to get the TNC of your choice and only hook up your
scanner's speaker output.
Here is one example of a decode-only circuit:
http://www.ringolake.com/pic_proj/decoder/rx_206.html
I have one of these in front of me right now decoding packets from an old
uniden police scanner found in my parents' basement. The down side to it
is that, unless you've got components and a programmer on hand, it's far
simpler and not much more expensive to go and get yourself a TNC-X kit
http://www.tnc-x.com/ or wait a bit until more kits are available and get a
Tracker2 (now in beta; I have one and it's great for APRS). If you're not
familiar with packet and hardware tinkering, you should probably wait a
while on the T2.
There are various decoder circuits out there; some use the MX614 modem chip
(Scott stocks 'em at http://www.argentdata.com/catalog/). Some use an
XR2211, and some use a simple zero crossing detector circuit. Most are
based on a PIC microcontroller of some variety.
The absolute cheapest way to go is with a software decoder like AGWPE (this
method in generally called sound card packet), but I found that to be the
most frustrating to get working, too. You may be able to get by as simply
as plugging an audio patch cable between the scanner and computer, but in
my experience you're not going to get far without including an audio
transformer and some attenuation.
-Jason
kg4wsv
------------------------------
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