[Autosail] Ardupilot and sensors

Thu Jul 7 11:44:16 EDT 2016

Sorry, yall. I'm still totally on board, but my Hacklab-life has been
pretty much taken over by the storm happening on the mailing list. I'll be
back on top of things soon!

On 7 July 2016 at 11:34, Trevor McKee <trevordmckee at gmail.com> wrote:

> 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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>>
>>
>
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-- 
Melissa Marie (emmy) Legge, BSW, MSW, PhD (c.)
(Pronouns: they, them <https://en.wikipedia.org/wiki/Singular_they>)
McMaster University
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