[Autosail] Ardupilot and sensors

[Trevor McKee]

Sorry I missed the meeting.

...do we have any plans for any sort of project management system thingey?
I use trello at work, may be useful in theory?  or a portion of hacklab
wiki?



On Thu, Jul 7, 2016 at 11:32 AM, Alan Majer <alanmajer at hotmail.com> wrote:

> Just a quick update on some of my To-Dos. Forgive me if I repeat info that
> others have already shared.
>
> *Ardupilot*:
> This thing has gone through a lot of iterations since I last looked at it.
> Seems like it's a choice between the newer but expensive Pixhawk, and the
> older arduino mega version that's cheaper but gets good reviews.
>
> The newest version, the Pixhawk, looks awesome (400Hz updates or
> something), but it's kinda expensive too at $200. It's also out of Stock:
> <https://store.3dr.com/products/3dr-pixhawk>
> <https://store.3dr.com/products/3dr-pixhawk>
> https://store.3dr.com/products/3dr-pixhawk
> Robotshop does have in stock (and I usually get their stuff in a week or
> so after an order):
> http://www.robotshop.com/ca/en/3dr-px4-pixhawk-advanced-autopilot.html
> There are much cheaper knockoffs on ebay (if we order now, probably take
> 4-5 weeks):
>
> http://www.ebay.com/itm/Pixhawk-PX4-V2-4-8-32Bit-Flight-Controller-NEO-M8N-GPS-Power-Module-Multicopter-/272240662408
> <http://www.ebay.com/itm/Pixhawk-PX4-V2-4-8-32Bit-Flight-Controller-NEO-M8N-GPS-Power-Module-Multicopter-/272240662408?hash=item3f62ced788:g:NjAAAOSw-4BXYQhc>
>
>
> Seems to be some discussion about 3DR signing their units in a way that
> locks you into their ecosystem causing interoperability issues. I haven't
> looked at this enough to know what's going on, just seems like a minor red
> flag to check out before we commit to Pixhawk.
>
> On the other hand, the slightly older version Ardupilot Mega (APM 2.8)
> still seems to be an interesting option (rated very highly but slower at
> 100hz... though this is a sailboat mind you). Although it's tougher to
> source, it seems that a lot of the most likely sources don't sell it, so
> hard to get a local copy. These guys are supposed to be makers of the
> official board but show out of stock:
> <https://www.unmannedtechshop.co.uk/ardupilot-mega-autopilot-kit-apm-2-8/>
> https://www.unmannedtechshop.co.uk/ardupilot-mega-autopilot-kit-apm-2-8/
> Hobby King looks like it has one though:
>
> <http://www.hobbyking.com/hobbyking/store/__56052__HKPilot_Mega_2_7_Flight_Controller_USB_GYRO_ACC_MAG_BARO.html>
> http://www.hobbyking.com/hobbyking/store/__56052__HKPilot_Mega_2_7_Flight_Controller_USB_GYRO_ACC_MAG_BARO.html
>
> As can be expected, the clone market is alive and well (some of these can
> ship via DHL to get it in a week):
>
> <http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20160707063654&origin=y&SearchText=ardupilot+mega>
> http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20160707063654&origin=y&SearchText=ardupilot+mega
>
> Also, sadly, I cannot find my old ardupilot (nor the GPS) that I had with
> it. It may have got consumed in another project or lent out to one. So look
> like we will need to purchase one either way.
>
>
>
> *Sensors:*Wind speed sensor. Yes, most of the weather monitoring stuff is
> pretty big, and around $100. But works well in very low wind speeds.
>
> Some options:
>  - weather vane atop of a cheap *rotation encoder* or *Potentiometer*.
> Not super accurate and probably has a bit of friction, but dirt cheap.
> Might be good enough, might be worth a test considering the price is right.
>  - Quality *encoder *with absolute position:
> http://www.usdigital.com/products/ma3   This one gives great accuracy.
> Not cheap at $60, but might be worth it.
>  - Then there's a bunch of traditional weather stuff.. both ultrasonic and
> weather vanes. This kit from sparkfun might be interesting (if a little
> big):
> <https://www.sparkfun.com/products/8942>
> https://www.sparkfun.com/products/8942
>
> Also, in watching some RC sailing videos, I think a normal weather vane
> may act weird at some of the sharper angles. We might want to consider some
> kind of weighted pendulum to keep it level.
>
> I also have a lot of other sensors kicking around... accelerometer,
> barometric, compass etc. We can figure out what we need. Stress sensor on
> the mast might be interesting. I've played with strain gauges a little
> (ones inside the wii) and they are pretty cool, but I seem to remember them
> drifting and calibration being an issue.
>
>
>
> *Weights:*
> Yes, I found the lead diving weights we could use if we want to melt down
> and cast exactly how we want it. Or if we don't care about the shape and
> need a quick and dirty solution i have lots of other heavy brass and steel
> pieces too (some are cylinders that'd be easy to put a nose on). If we are
> even less picky (or want to test specific weights before casting) I have
> some iron barbell weights that we could pretty much use as is if we
> attached them to some kind of steel/aluminum flat.
>
>
>
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