Hi Scott,

You got it. To some extent you're waiting on Dave to figure out what our
maximum charging current is, but you should be thinking about the ideal
diode circuit between the umbilical and battery, how we might sense if
there's voltage on the line (probably just a "powergood" signal on the
battery charger), maybe think about launch detect, etc.

We'll talk more on Friday.

Andrew

Scott Schuehle wrote:
> Hey guys,
> It's a nice coincidence that you're talking about the umbilical, because
> I have been trying to start some research on this topic.  After reading
> your discussion below, I think I'm a little unsure as to what I'm doing
> with this part of the design.  Per the discussion below, the connector
> is already chosen, so is integrating that connector into the APS what I
> should be focusing on?  Also, is there documentation on the wiki about
> the umbilical?  I feel like I've poured over the APS design
> documentation, but can't really find too much about this.  Any
> help/suggestions would be greatly appreciated!  Thanks!
>  
> Scott   
> 
> On Mon, Feb 2, 2009 at 10:53 PM, Andrew Greenberg <and...@psas.pdx.edu
> <mailto:and...@psas.pdx.edu>> wrote:
> 
>     Hi David,
> 
>     The shore power connector on the rocket connects has three purposes:
> 
>     1. It conveys power ("shore power") to the rocket to charge the
>     batteries and run the avionics system during testing or before launch.
>     Shore power either comes from a power brick plugged into the wall, or it
>     comes from a 12V to 20V DC-DC converter that runs off of the launch
>     tower computer's solar-recharged lead-acid battery pack. You can see the
>     solar panel, batteries, and launch tower computer here:
> 
>     http://psas.pdx.edu/Lv2LaunchTowerElectronics/ag_lt_ltc.jpg
> 
>     2. It allows us to talk directly to the APS microcontroller using a
>     three wire UART (TX, RX, GND).
> 
>     3. It acts as one of many launch detect sensors: when we're armed for
>     flight, and the launch tower computer fires the igniter, then the shore
>     power connector being yanked out pretty much means you've launched. Of
>     course it's never that simple, because the cord could fall off by
>     accident, or the connector could get jammed, etc. We have a fancy lever
>     mechanism for pulling the plug out of the socket on launch; when we
>     break out the launch tower computer this spring for testing, we'll show
>     that off.
> 
>     The connector we're thinking about using is a high reliability medical
>     connector that has just the right properties: it's keyed, it slides out
>     easily, it doesn't jam, and it has high current capabilities. I don't
>     have the part number right now, but eventually we'll post it to the web.
>     Right now we're thinking of a seven pin connector:
> 
>     2x V+
>     2x GND
>     1x TX
>     1x RX
>     1x Launch detect (shorted to ground)
> 
>     We'll have a short "on the bench" cable for testing, and we'll have a
>     very long (~ 20 ft) cable that goes from the LTC to the rocket for the
>     actual launch.
> 
>     Andrew
> 
>     da...@cecs.pdx.edu <mailto:da...@cecs.pdx.edu> wrote:
>     > hey,
>     > doing some research on the charger, and am curious as to what type of
>     > external connection we will have, are we simply plugging into an
>     outlet,
>     > or are we dealing with a cable of some sort?
>     >
>     > David
> 
>     --
>     -------------------------------------------------------
>     Andrew Greenberg
> 
>     Portland State Aerospace Society (http://psas.pdx.edu/)
>     and...@psas.pdx.edu <mailto:and...@psas.pdx.edu>  P: 503.788.1343
>      C: 503.708.7711
>     -------------------------------------------------------
> 
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> 
> 
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-- 
-------------------------------------------------------
Andrew Greenberg

Portland State Aerospace Society (http://psas.pdx.edu/)
and...@psas.pdx.edu  P: 503.788.1343  C: 503.708.7711
-------------------------------------------------------

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