Jim's Posts (4)

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Alternative 868mHz transceiver for Europe

TINY-500.jpg?width=350Hey Folks.

While looking around on the interwebs today for alternatives to the Digi Xbee 868 modules for use in Europe, I found this from http://www.rfsolutions.co.uk.  It's specifically the Tiny Pro with external antenna that caught my eye. (The photo above is from the smd on-chip antenna version)


  • High Power - Up to 500mW
  • Serial Baud Rate 1.2 to 115.2Kbps
  • RF Baud Rate up to 38.4Kbps
  • Range up to 4KM using external antenna

From the manual for the TinyPro:

"This band is free to use but the module and the user must respect  some limitations. Most of  these restrictions  are  integrated  in  the  conception  of  the  module,  except  the  duty  cycle.  The  869.400  to 869.650 MHz band is limited to a 10% duty cycle. This means that each module is limited to a total transmit time of 6 minutes per hour. It is the responsibility of the user to respect the duty cycle"

It looks fairly expensive, and I don't think the baud rate is as high as the Digi modules, but asking the user to enforce the duty cycle would allow us much more control.  Assuming we wouldn't just ignore the DC entirely, we could allow the APM to control it rather than having to hack it as the current thinking on the digi 868's suggests.

Has anyone tried this, or have any comments on suitability? Perhaps there are other 868mhz modules out there who also have less draconian enforcement of the DutyCycle?





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Twinstar APM takes to the sky!



Today I flew my Twinstar with APM in the hotseat. It's the second flight I've had with it wired in, but yesterday I was only using the stabilise mode. It's been a couple of great days from a weather and wind point of view, so ideal for testing.  The Stabilise mode is lovely.  The Twinstar (mine has a stock power system) when it is trimmed up is a super stable platform anyway, so I'm not too surprised that stabilise didn't have a massive impact, but it was certainly noticeable and very pleasant to fly!  The plane does have about a 5 degree nose down pitch when hands off (in stabilise) and I don't know how to fix this, can it just be trimmed out with the radio?  I thought the AP would compensate for any trimming I did to the control surface, and the fact that it has a nose down attitude is probably an autopilot config issue.


Return to launch was interesting.  I took off in stabilise mode and flew fairly straight away into the wind gaining a bit of altitude.  I then changed mode to RTL and took my hands of the control for the next few minutes.  The plane held attitude well, and executed well controlled turns.  However, you couldn't in all honesty describe what it was doing as a circle overhead the launch site.  Figures of eight perhaps, it seemed to be hunting for something.  It certainly seemed to be controlled and comfortable in the sky, I wasn't too worried.  I still don't understand it's behaviour though.


I would like to share the log file with you, but I can't.  For some reason this flight wasn't logged.  The previous two were and I have the KML and log files for those (not huge files, probably about 3-4mins flying each). Log three only shows one 'page' of data.


I will fully admit that this may all be my own fault.  I'm still learning, but in my excitement and the heady sense of progress, I havn't run the tests and tuning using FBW_A that the manual suggests that I should do.  I've not got my head around PID settings, and I suspect that this is the root cause of the issues i was seeing with RTL.  I'm guessing the AP couldn't hit it's mark to begin the orbit.


If the weather holds I'll be out again tomorrow to diligently follow the FBW_A tuning guide!



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First flight coming up!

Hey Guys.

4712248374_fd0d27630c_m.jpgJust wanted to let you know that after what seems like ages playing with wires and getting things working, it looks like we are about to take to the air for the first time with the Ardupilot and ArduIMU installed and active. 'We' are a team of three from the UK ( Jim, Paul and Iestyn) who have decided to get into UAVs for the engineering challenge. Iestyn and Paul (but not me!) have solid RC plane experience, while I'm bringing the Arduino and software experience. If the weather is in our favour, we hope to fly some time next week. Progress has been tortuously slow, as we are only able to work on this and fly during lunch hours at work!

The plan is to fly on manual with all the systems installed and wired up, so that we can make sure we are comfortable with the weight load, power and COG. If we are happy we will flick it over to stabilisation mode and see how the gains look and feel. Before flying we'll do a full test of the systems on the ground, including checking for servo reversing.

I don't think there are any questions right now that haven't been answered in the forums or the on-line docs, but I would like to just check a couple of things. We are going to be using a DX6i radio to fly with, but it only has a two position switch (I'm planning on using the 'gear up/down') for the (mode) control line. I don't think this will be a problem will it? (other than only having one AP option to fly with!). When the switch is toggled, which mode will be active? (Stabilisation or Fly-By-Wire? (I've not changed the defaults)).

Has anyone got any useful advice for our first flight? Perhaps things they know now which would have been useful back then. What can we expect to see in an airframe running in stabilisation mode that is running with stock settings for the gains, big oscillations?

I'm planning on trying to capture telemetry via the laptop through a pair of Xbee's. They are the low power versions so I they will be dropping in and out of range quite often. I haven't got my head around the various Ground Station projects yet, in fact I plan on writing my own (yet another half baked GS). Is there a link to the autopilot telemetry protocol, and perhaps a recommended existing GS project? (I'm sorry, I've not done any research here, I should be able to find these myself).

I'm keeping a project wiki for this, you can see it here if you are interested. I'll post back with results good or otherwise...

Wish us luck and light winds!


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Games tech of interest?

Hey Guys.

I know some of this has been discussed before, but does anyone want to speculate on how interesting the MS project Natal (now called Kinect) and the rumour that there may be a 3D camera on the new Nintendo DS could be for amateur UAVs?

Would a 3D camera be useful to us? I'm guessing not really on a relatively high altitude (>10m) fixed wing airframe, but perhaps for multi-rotors it would be great. If the 3DS really does contain a 3D camera, it's going to be tiny, and that could be very useful! I'm also building a AGV, and I expect that I'll be in the queue to get a "kinect" come november.

It's E3 this week so expect lots of interesting (and otherwise) games industry related tech releases in the press.

Nintendo 3DS:

MS Kinect

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