After fiddling on the bench a lot, I've concluded that the source of the noise (most of it anyway) is small variations in the power supply voltage (3.3v) caused by load from the servos and radio (which draw on the same battery, but prior to the 3.3v regulator). I can see the altitude readings jump around each time a servo draws current. To get rid of the noise, I think I need some way to make the 3.3v supplied to the sensor (and to the ADC reference) extremely smooth and noise-free; but I'm not sure how to do that.
If someone thinks they can help, let me know and I'll post schematics of what's there now.
Either get a linear regulator with better specs, put a pi filter in front of your regulator, or just use a separate battery for the sensor's regulator. A 2 gram Lipo would work well for that.
The electronics should consume a tiny amount of power compared to your servos, so I wouldn't worry about the 1/2 power loss for that part.
I would expect #1 to provide the best performance by far. Linear regulators are designed just for this sort of application.
What GPS are you using? SIRFstar-based units go crazy in rockets in my experience.Another possibility is that there is something about the glider flight dynamics that the GPS firmware can't handle.
What GPS are you using? SIRFstar-based units go crazy in rockets in my experience.
What GPS are you using? SIRFstar-based units go crazy in rockets in my experience.
Maybe this the answer to question about the GPS malfunction is here.
That's the one that DIYdrones sells, though they use custom firmware for it.It's the GlobalTop PA6B, based on the MediaTek MT3329 chipset.
Any details on this? I reviewed the Mediatek documentation and didn't see anything.It turns out there is a dynamics setting in the GPS chipset I didn't know about - I'm going to check how this was set...
Any details on this? I reviewed the Mediatek documentation and didn't see anything.
Regarding the dynamic conditions, you can execute PMTK command for setting. Our output speed is horizontal speed not vertical speed. Also, we don’t have higher accelerations.
PMTK command:
$PMTK302, MODE
Mode: Dynamics mode.
0 : Default ( fixed status)
3 : Slow Ground Vehicle (tractor, boat etc)
4 : Fast Ground Vehicle (car, train etc)
5 : Airbourne Low dynamics (<1g)
$PMTK302,3*2C<CR><LF>
//
Query Dynamics type
$PMTK402*34<CR><LF>:API_Query_Dynamics
We got 302 & 402command data from MTK, but we don’t verify them, so we don’t list them in the manual.
Thanks for the info!This is what I was told (pasted from their email)
I'm wondering if there's some kind of EMI problem given that these GPS chipsets appear to work better than this in general.Analysis of the telemetry showed that the GPS had lost lock again...
I'd have thought that the dynamics settings only affected the filtering, not the lock per se. Also, this GPS chipset has been used in rockets before (both by Dave and others) without these sorts of problems as far as I know. I'm sure Dave has thought harder about this though.If the "low dynamics < 1g" is a hard constraint...
I'd have thought that the dynamics settings only affected the filtering, not the lock per se. Also, this GPS chipset has been used in rockets before (both by Dave and others) without these sorts of problems as far as I know. I'm sure Dave has thought harder about this though.
Looking at the video, it looks like it was pitching over during and after the boost, and there were high Gs throughout the flight.
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