|Feb 26, 2014, 01:06 AM|
Hobby King RX3S Gyro
Hobster shared some great info on the RX3S v2.1 gyro from Hobby King in the Stab thread. It's under $20 and apparently pretty capable, especially with a flash upgrade to the firmware:
A few of us have picked them up and will be testing them in some light foam shortly. This can be a place to share information about the unit.
I won't be flashing mine since that would require some extra gear, but even bone stock, the gyro can be turned on and off remotely via a spare channel on the rx. It can handle elevons out of the box too, but if you want remote gain adjustment and flaperon capability, it will need the upgrade.
I got mine less than a week after ordering as they shipped from Utah even though the hobby king site said they were coming from China.
There are no instructions included.
I have no delusions about this being a replacement for a futaba gyro or something higher end - but my curiosity about gyros for DS has gotten the better of me, and I want to see what can be done with a simple two channel foam plane that will be DSing within a small speed range 90% of the time.
I'll report back with my findings. Meanwhile, post away.
|Feb 26, 2014, 02:57 AM|
FWIW: I've tried the Eagle Tree Guardian for DSing in a foam plank:
This was the one that held the most promise (well, that I thought anyway). I found that for lighter days running it 3d mode possibly helped with the gain down to about 30-40%. But the one day I tried it in heavy winds (120KPH) everytime it crossed the shear it got itself into a bad feedback loop/oscillation and it made a bad vibration/farting sound each time it crossed - the sort that could tear a plane to bits. Each time I dialled the gain down until it was at zero before it stopped the feedback.
So it seems it simply cant deal with the extreme speed ranges and extreme accelerations encountered in DSing. I found I could fly as well, if not better with it off.
I know others have tried these and have had more success with them - in a larger tailed model tho. For me, I wont bother with this unit again - espc given the extra complexity of wiring and mounting it etc. I think tip-weight (mass-damping) works as well as damping out uncommanded changes in flight.
|Feb 26, 2014, 02:48 PM|
Hi Dominic, all the best with your gyro trials. I am awaiting two more units from Hobbyking, along with the special lead that sits on the chip and will (hopefully) allow me to reflash... I've installed the drivers and software on my PC, just need that little brown cardboard box from Hongkong to arrive...
As the stock rx3s unit doesn't allow tx gain control, I would start with the gains set very low initially and increase from there (and less elevator gain than aileron gain on a plank). If the plane oscillates there's too much. I am thinking of trying one of the reflashed units in an Opus to see how it compares with the futaba gya351 that I've been using. The futaba is single (aileron) axis only, unlike the orange. I've been DSing 2 or 3 years now with gyros (up to 276 with my 'Penetrator') but not had the problems taurineman experienced. To me, turning on the gyro feels like the plane has gone up a size in weight and span.
|Feb 28, 2014, 06:58 PM|
big wings, but I'm sure it's not going as fast as your plank. Have you turned the
aileron pot gain down on the Guardian, or just the remote gain? I think
turning the pot gain down might help as it seems to limit the throws and
gives you more resolution with the remote gain. The problem with Guardian is that
it does not implement a proper HH algo in 3D mode. If the stick is centered,
then it will behave like a HH gyro and continue to try to roll back to whatever
orientation the aircraft was in when you centered the stick. But the moment you move
the stick off center (or are forced to trim it off center), it reverts to rate mode which
is purely reactionary, and no longer tracks the angle. When turbulence causes aircraft to
roll at some rate of rotation, the gyro responds with an impulse to counter only that
rate of rotation, but doesn't care where the roll started, or where it will end.
Pure rate mode always requires less and less gain as you go faster because
the effective response of the gyro increases with more airspeed over the surfaces.
It sounds like the HH mode on the flashed RX3S Gyro is much the same as Guardian.
Only works at center stick.
My old ACT Fuzzy Pro (the one in my cheater D60) does real HH on top of input rate
request. In other words, if the stick is centered then the requested rate of rotation
is zero, and as turbulence tries to push the aircraft off axis, the gyro
keeps pushing back until it returns to original orientation. If the stick is moved
off center, then it means you're requesting a specific rate of rotation, and the HH logic
stabilizes on top of that rate of rotation. If you request a 90 degree per second
roll, then in one second it will be exactly 90 degrees from original
orientation, even if turbulence is knocking it around on the way there.
With proper HH behavior it's less prone to speed wobble, because
the magnitude of the response is proportional to the angle of error rather
than just the rate of error. A small fast bump causes a large rate reaction
but a fairly small HH reaction even at very high speeds. I can set my gain once,
and never touch it again from launch to 250mph.
What I might try next is one of my CC3D multirotor boards in airplane mode.
Its "Rate" mode has full PID tuning so it's really more than just rate response,
and it also has an "Axis-lock" mode which is much more like a true HH response.
The TxPID feature allows any single tuning parameter (P, I, D and more) to be adjusted on
the fly on one or more axes at once.
|Mar 03, 2014, 11:47 AM|
Successfully reflashed my Orange Rx3s with the Open Flight Stab firmware.
I didn't find the process entirely straightforward. I used the 'avrdude' software to perform the reflash - the gotcha for me was figuring out to use the avrdude that comes with the Arduino installer.
Thought I'd post my notes in case they are of use to anyone else. Please only follow at your own risk! Also read the the official guide https://docs.google.com/document/d/1...h.ljwnuss3tu59 and heed the warnings before proceeding ...
I also followed this helpful guide http://blog.itsnotfound.com/2013/08/...e-orange-rs3x/ but there is a line in there which I would skip (explained below)
Orange Rx3s v2
USBasp AVR Programming Device for ATMEL Processors (off ebay, make sure the jumper is set to 3.3v NOT 5v!!!!)
Atmel Atmega Socket Firmware Flashing Tool (from HobbyKing)
Software Required (assuming Windows PC, I am using Vista but 7 should be the same - maybe Win8 too?)
1. Get the open flight stab from here https://github.com/noobee/FlightStab
Look for 'Download Zip File' button at bottom right. Need the .hex file from the Builds folder inside this zip (20140208_RX3S_V2.hex in my case) and put in the c:\ folder. The hex file is the 'firmware' that gets written to the chip
2. I next installed USBasp drivers from here (these allow the PC to talk to the usbasp usb thingy)
3. I next installed Arduino (1.0.5 when I did it) from here http://arduino.cc/en/Main/Software#toc2
click on 'Windows Installer' link to download. This took a while to install.
4. Avrdude.exe is the program that installs the new firmware. I used the avrdude from the directory created by the above install in the Arduino directory - in C:\Program Files\Arduino\hardware\tools\avr\bin
I copied the avrdude.exe in this folder to my c:\ folder. I also have the hex file (20140208_RX3S_V2.hex in my case) in the c:\ so that I dont have to write long paths
Aside: It was part 4 above that got me stuck. Mostly I followed http://blog.itsnotfound.com/2013/08/...e-orange-rs3x/ but the bit that got me stuck was where it says "To download and setup AVRDude for Windows follow this link." Skip this, the avrdude in the link is not compatible with the current arduino conf file (gives an error on line 332 of the conf file ). Instead I used the avrdude.exe as described in my point 4 above which worked)
The above blog (blog.itsnotfound...) shows how to position the Atmel Atmega on to the chip (white dot on the board and red dot on the Atmel tool align) then give the commands to erase the existing firmware and then reflash with the new firware. For completeness, the command I used to erase and rewrite the new firmware were, respectively (using my paths and hex file build and running the commands in the C:\ folder location)
avrdude -C "C:\Program Files\Arduino\hardware\tools\avr\etc\avrdude.conf" -c usbasp -p m168p -e
avrdude -C " C:\Program Files\Arduino\hardware\tools\avr\etc\avrdude.conf " -c usbasp -p m168p -U flash:w:20140208_RX3S_V2.hex
|Mar 03, 2014, 12:16 PM|
Another option for flashing is the http://lazyzero.de/en/modellbau/kkmulticopterflashtool
It already has full support for this gyro (it's listed in the drop down menus, along with
current flash version). Generally seems a little easier to get installed and working than
avrdude, although I've used both.
Having 3 hands really helps when you get to the actual flashing part, when
you use that HK Atmel Atmega flash tool. It's really fiddly getting it
positioned on the chip, and hold it in place, while you simultaneously
try to execute the commands on the computer.
|Mar 03, 2014, 03:23 PM|
|Mar 03, 2014, 05:28 PM|
|Mar 10, 2014, 01:03 PM|
Basic question on this thing: how does one connect it for elevon/plank use? I switched the elevon dip switch to "on". I gathered that the the lower 4 ports are "in" (from rx) ports and the upper 4 are "out" to servos. Beyond that, I can get both left and right working in both pitch and roll.
Thanks in advance for any insight!
|Mar 10, 2014, 02:05 PM|
|Mar 10, 2014, 02:37 PM|
I should have been more prepared when I ordered and added the male to male connectors needed to go from rec'r to gyro.
Here are two of the most useful links from the HK website...
review/instructions - can be translated from French
Edit: a vid is even better. Cheers Hobster.
|Mar 12, 2014, 01:04 PM|
Thanks for all the help guys. Got it wired and working well. Only rub is that I installed the unit with the long side spanwise instead of chordwise, so my gain for roll corresponds to the pitch axis and vice versa. Should have hammered that out before I mounted it, but it does't seem like it will make a difference?
Hopefully will get the plane covered and maidened on Saturday.
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