[altusmetrum] TeleMetrum In-Flight Reset
keithp at keithp.com
Mon Feb 13 23:25:15 MST 2012
On Mon, 13 Feb 2012 21:14:49 -0800, Casey Barker <casey at barkerzone.com> wrote:
> The TeleMetrum was configured for a 2-second apogee delay and did fire a
> Rouse-Tech CD3 (CO2 cartridge) for drogue. I think the use of the CD3 is
> why there's not much of a bump. The Raven was set for 4 seconds and
> connected to a BP squib. I know the Raven blew after the TeleMetrum
> because there was no BP residue inside the airframe (unlike for the
Ah, all is clear now -- the 2 second delay was internal to the TM. The
TM reset just under two seconds after apogee. (apogee at +27.68s, last
data at 29.49s). TM would have sent a couple of packets past apogee
indicating drogue state; perhaps they were just lost?
> For what it's worth, on my first flight of this unit, I misconfigured the
> Raven and it fired the drogue BP a couple seconds early. In that flight, I
> saw a clear pressure spike in the TeleMetrum data when the Raven blew the
> drogue, and later, the TeleMetrum successfully fired the main CD3 with no
> apparent bump. (It then reset immediately after deploying main.) So it
> seems like a similar issue as last time, but just reversed
Yeah, it's like your board doesn't have the fix installed; once we stuck
a cap across the LDO input, we couldn't cause *any* kind of voltage drop
on the 3.3V rail.
> I don't think this is it, based on the above description. But I have gone
> through the Raven's flight cycle on the bench, and it doesn't seem to
> interact with the TeleMetrum. I was actually thinking that a feature
> similar to the Raven's "simulated flight" would be really useful on the
I've thought about this. I coded up bits of it a few months ago; of
course, it would require talking to the TM board over USB, which makes
it less than ideal from an electrical perspective.
> Being able to fire charges on demand is oh so helpful (more
> useful than the Raven, frankly), but it doesn't properly simulate the
> combination of firing charges and tx'ing live telemetry. I think that's
> where the issue lies. I've poked around the TeleMetrum code, but I don't
> know it well enough to add this feature myself yet, and I'm not sure
> there's room for it.
Yeah, it's always a tight squeeze to add anything to the TM code.
> In short, it's all #20 stranded copper wire, with a tight twist in all the
> leads to switches and igniters based on the RFI lessons learned in my 54mm
> Little Dog. The wiring harness uses the 4-pin 3M connectors and the rotary
> voltage switches from the Altus Metrum site. All of the wiring is
> completely independent from the Raven, and the Raven is on the opposite
> edge of the bay, as far away as it can be in a 5" airframe. I'll send
> photos in the next day or two.
Sounds really clean. Let's see if Bdale has any other suggestions on how
to test stuff; if I had the board in hand, I'd hook up a meter to the
3.3V rail and then take a high power transmitter (like a regular HT) and
see if I could get it to drop at all by holding it near sensitive bits
of the TM. That's how we diagnosed the missing capacitor issue...
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