(discussion moved from the TRA list & some private emails)
A bit of background - I'm an EE and work in oilfield automation and safety
engineering, I have some (dated) background in microcontrollers. I'm also a
CAR RSO. I used Adrian's magnetic switches last year on my N1800 L3 project.
They work well, though we've found that they tend to be a bit sensitive to
stray magnetic fields - got to be careful where the cell phone, radio,
pocket with magnet, etc. are in relation the sensor.
I understand the concern about potentially launching a rocket with the
recovery system turned off, but I think the case of a rocket that won't fly
but has armed ejection circuits is also worth consideration. In Canada we
require a sterile ballistic recovery zone so odds of anybody getting hurt by
a ballistic recovery are low, but we often have incidents where a rocket
fails to fly and has to be lowered off the launcher - I consider the danger
of accidental deployment during this process a much higher risk since people
are close by. Obviously if the rocket has accessible switches there should
be no problem, but there is the potential for this to be an issue.
Personally I love the idea of remote arming and disarming, beats climbing a
rickety ladder and eliminates access hatches / holes.
I think that allowing bi-directional comms prior to launch detection would
be a valid approach IF a launch detect routine could interrupt a radio
subroutine. It could also automatically force the TeleMetrum into flight
mode, and the listen mode could be disabled.
My question is how well does the processor multi-task? How much room is
there for more code, and how fast does it all run? Does the launch detection
subroutine run on a timed interrupt basis? The radio routines take a long
time to execute due to the need to transmit and receive data at a much lower
data rate, but most of the CPU time would be spend in wait cycles as the
data is buffered through. Ideally they are not exclusive program calls that
block other routines from running, but maybe I'm assuming too much from this
particular processor?
Regards,
Eric
-----Original Message-----
From: Bdale Garbee [mailto:bdale@gag.com]
Sent: Tuesday, February 07, 2012 22:45
To: Eric Weder
Subject: Re: FW: [CRA] CRA Twitter Update
On Tue, 7 Feb 2012 14:33:23 -0700, "Eric Weder" <eaweder(a)yahoo.com> wrote:
> Once the rocket is set up and TeleMetrum is armed in launch mode, what
> happens if you have to take the rocket down? Easy case is that it has
> an external power switch, but what if it is not accessible and you
> have to leave the altimeter armed while lowering the rocket?
Once a TeleMetrum is in launch-detect mode, there is no way to take it back
out over the radio. There are two reasons for this. One is that if we
happened to detect launch while the radio is in receive mode, we'd lose the
ability to collect telemetry briefly until the radio got turned around to
transmit. The second is that several early customers were adamant that
there be no way to accidentally take a unit out of flight mode over the
radio once igniters are installed in a rocket on the rail.
So, we strongly recommend having an externally-accessible power switch.
Taking a rocket down from vertical with the electronics still armed is not a
good idea. Adrian's magnetic power switches from Featherweight Altimeters
can be used with TeleMetrum boards, I'm happy to provide wiring details if
mechanical switches bother you and you want to go that route instead.
Bdale
When I have the Telemetrum in flight monitor mode, I get RSSI, lat and long, the things as expected. The RSSI is stable, lat and long become stable, voltage may drop 0.01V every couple minutes. That is cool, everything looks like it is operating fine.
If I remove power to the Telemetrum, the HMI does not change. Not unexpected...nothing to tell the HMI to change
The problem I am having is that once everything is stabilized I no longer have an obvious indication that it is all working. My best option has been to go look in the table and check the temperature...it fluctuates quite regularly every couple seconds or so. That gives me confidence I still have a downlink from the Telemetrum. But doing that seems to be a awkward way to check the link.
Is it possible to provide on the Monitor Flight HMI some sort of indication of link activity. Similar to the blinking light on the Teledongle. Perhaps a screen age thing, as in this screen data is one second old, five seconds old, 5 minutes old. Something that tells me I'm getting data, I have a data link. No data link, no fly.
Or zero out lat and long on no data?
Maybe I'm not looking in the right place.
Thx
Ron Veale (32.937716 -112.680762)
CAR S699 L4 RI3, TRA 10019 L3, APRS:VE6RAV-7
On my MacBook, when I press the load maps button, the button turns blue and there is no more activity. Do not get the HMI to enter lat and long for an unknown site.
Works fine on Windows7 for me.
MacOS 10.7.3
About Altosui, Version 100.0. Wow!.
In AltosUI Configure, 1.0.3
I do get a google map however of my current location. Concerned that once on site may not have IP connectivity.
Can always live I guess with just the lat and long if using the mac.
Ron Veale (32.937716 -112.680762)
Director, Canadian Association of Rocketry, Alberta Region
CAR S699 L4 RI3, TRA 10019 L3, APRS:VE6RAV-7
Well, not new really, new to altusmetrum.
49°26'44.23"N 112° 0'42.51"W
http://www.lethbridgerocketry.com/roclake/
Ron Veale (32.937716 -112.680762)
Director, Canadian Association of Rocketry, Alberta Region
CAR S699 L4 RI3, TRA 10019 L3, APRS:VE6RAV-7
Hi list...
just recently joined.
Haven't seen too much activity here, other than the restart discussion.
Just bought a Telemetrum. One flight, worked great!
Have a BeeLine GPS. Several flights. Works great!
Have an ARTS 900MHz GPS Telemetry System. A few flights. Currently in storage.
Had an AGTS from ATHA a few years ago. Forever lost in bits and pieces due to shred.
Have an interest in parsing further data from the GPS NMEA, in particular VDOP or PDOP.
VDOP in order to qualify the accuracy of the altitude measurement. Ie something like "68% probability that the altitude is within +/-20m".
Just not sure at this time if that can be claimed or would be accepted. Need data!
I need a couple more flights before suggesting other thoughts.
Should be fun!
Ron Veale (32.938676,-112.677424)
CAR S699 L4 RI3, TRA 10019 L3, APRS:VE6RAV-7,13
Hi folks,
I returned my two TeleMetrum units for the prescribed capacitor and got
them back last month. I flew one unit (#340) on 2/4 in the same
configuration as described before (5" rocket on an M motor). I didn't see
any issues in my ground tests, but the TeleMetrum reset again during
descent, this time just after drogue. The on-board camera heard it
resetting into "idle" mode. Fortunately, the backup Raven got the main
out, so no harm done.
I've attached the .eeprom file. It ends shortly after the drogue, but the
ground station never actually called out "drogue," so I don't think that
last packet made it out.
In total, unit #340 is 0-for-2. I haven't flown the older unit (#301,
previously 1-for-2) since the rework, but I might try it next month. Any
additional thoughts on how to improve reliability here?
Casey
