Surviving Flight Recorder Power Failures

It will provide a log file adequate for use at most contests. YMMV--contact
the CD to make sure

"ContestID67" wrote in message
oups.com...
One of the main points is to protect the recorder so that you retain
your all important log file. While what you propose will get you back
home, it won't produce a valid FAI log file.

X-no-archive: yes
In article .com, 5Z
writes
I think there have only been a small handful of failures out there so
far.

If the electrical system is clean and put together well, then the
chance of a failure is probably too remote to worry about.

FAI and contests allow for a gap of several minutes, so a simple switch
for dual batteries is good enough if you're worried about the battry
running out on you - or you forget to charge one.

As you say, most recorders will only start a new file after power has
been removed for about 5 minutes, which is provided for in the current
FR Specification.

However some earlier recorder, the Volkslogger for example, were
designed before this provision was written in, and will always start a
new file after a power-down, regardless of duration.

Even then, if it is 'beyond reasonable doubt' that there was no
intermediate landing, more than one file may be accepted.

Tim Newport-Peace

"Indecision is the Key to Flexibility."

On Thu, 16 Jun 2005 09:37:07 -0700, ContestID67 wrote:

I agree that a couple of diodes are the way to go to place the
batteries in parallel without allowing one battery to cause problems
with the other. However the key is the voltage drop which is typically
0.6vdc for a power diode. Do you have a specific diode number that you
have been using?

I used two IN5817's. I only use these to power a Volkslogger. The rest of
the panel is still controlled via "A/B" switches.

These are rectifying diodes with low forward voltage drop, especially at
low currents. In my setup I think I loose less than 0.2V but it is tricky
to measure. These are small diodes with a Max current rating of about 1A.
I don't think that you could power your whole panel through them. (Google
should find you a data sheet).

Having the switches for the heavy current items (transponder etc) is
useful. It is very difficult to test the health of a battery on the
ground. So you normally only discover that the battery is not up to
scratch when it dies while you are flying. At this stage it is nice to be
able to switch over to battery B.


Ian

I use either 1N5401 or NTE5802 diodes ahead of my master
switch, so they are powering my whole panel. I understand
that they have a 3 amp capacity. I've never had any
problems with them. I recollect that they have a 0.6
V drop, so I don't have to worry about switching batteries,
the diodes do that automatically when the battery in
use drops to 0.6 V below the battery not in use. It's
very convenient. All I have to do is select my higher
voltage battery before I take off.

I can't take credit for the idea or design. I got
it from Nick Bonniere.

At 04:48 18 June 2005, Ian wrote:
On Thu, 16 Jun 2005 09:37:07 -0700, ContestID67 wrote:

I agree that a couple of diodes are the way to go
to place the
batteries in parallel without allowing one battery
to cause problems
with the other. However the key is the voltage drop
which is typically
0.6vdc for a power diode. Do you have a specific
diode number that you
have been using?

I used two IN5817's. I only use these to power a Volkslogger.
The rest of
the panel is still controlled via 'A/B' switches.

These are rectifying diodes with low forward voltage
drop, especially at
low currents. In my setup I think I loose less than
0.2V but it is tricky
to measure. These are small diodes with a Max current
rating of about 1A.
I don't think that you could power your whole panel
through them. (Google
should find you a data sheet).

Having the switches for the heavy current items (transponder
etc) is
useful. It is very difficult to test the health of
a battery on the
ground. So you normally only discover that the battery
is not up to
scratch when it dies while you are flying. At this
stage it is nice to be
able to switch over to battery B.


Ian