Hi Guys,
The antenna pad on my TM V2 was ripped off the board during a hard landing
last month. My plan is to epoxy the pad back onto the board and then solder
a thin wire from the output of C177/U174 to the antenna wire. I've also
thought that converting the board to an SMA connector might be a more
rugged solution.
Any suggestions?
Thanks,
Chris
I have a question regarding an issue with my TeleGPS this weekend at
NXRS. It quit transmitting data almost exactly at apogee (12,000 feet)
but it continued to save data to the EEPROM until it lost power at main
chute deployment. Ballistic deployments are heck on things. I don't
remember what the battery voltage was when I launched it but it was
reading 3.8 volts when I got home after sitting for 24 hours with no
load. I have flown this quite a few times now with no similar issues.
Terry
How long is the current delivered on a Telmetrum, Easymini, or other Altus
Metrum products to the ematch output terminals? Is it dumping full battery
voltage, or just a bit under battery voltage? I guess I could hook up my
scope, but I'm lazy, so I' thought I'd ask. I'll get out the scope if I
have to.
The reason I ask is I was trying to come up with something I could use for
testing computers in my "test dummy" rocket. Let's say I wanted to test a
Telemetrum, Altus Metrum or other rocket computer product by putting it
through a flight without actually using it for ejection. Rather, if I use
other ejection method (like direct motor ejection) and connect the computer
in a protected AV bay compartment to something like a small fuses to mimic
ematches that would blow when it got voltage applied, this would indicating
it did send current to the output. (Wouldn't tell me when it fired, but
would indicate it was working in some fashion. The log file would tell me
when it fired. ) I could always use an actual ematch for the test, but
then I've got something combusting inside a tube with no actual ejection
going on. The test area is isolated from the computer compartment.) I
could make my own ematch with no pyrogen on it, but I'm trying to keep this
simple with off-the-shelf parts and without actually combusting something.
A small glass fuse with visual indication would be a great choice.
I bench tested my Telemetrum with a pico fuse I had on hand (.062A), but the
fuse never popped. A .062A Pico II fuse has a 7 ohm internal resistance.
It was connected directly to the Telemetrum's terminals. On paper, it sure
seems like it should have popped, but perhaps I'm making a bad assumption on
a technical detail. If I assume I get 3 volt at the terminals; according to
the Pico II fuse spec sheet, it should pass 428 mA (3V/7 Ohm) and pop in
less than 1mS, but it didn't. Something like a 300 mA glass fuse has a
lower internal resistance at about 1.6 ohm and would give me a visual
indication. If I assume the same 3 volts across the terminals during
ejection, I should get 1.8 amps across a 1.6 ohm, which should blow a 300 mA
glass fuse in less than 20 mS. But I'd need to know the actual voltage
across the terminals and for how long it fires.
The Telemetrum fires an actual ematch with no problem in a bench test.
Pico Fuse spec sheet
http://www.littelfuse.com/~/media/electronics/datasheets/fuses/littelfuse_fu
se_251_253_datasheet.pdf.pdf
Glass Fuse spec sheet
https://www.parts-express.com/pedocs/specs/fast-acting-fuse-235p-series-spec
ification-sheet-specifications-45682.pdf
Scott Myers
