John Grouse's Posts (5)

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I now have an RCTimer OpenSource BGC board ("Martinez") and a couple of LD-Power Gimbal Motors which are large enough for an NEX or smaller.  I looked over a number of BGC frames for sale but they all seem to incorporate metal or glass fibre, both of which do not have the same strength and low weight of carbon fibre.  Based on the connection system I had used on the first CF gimbal I built from scratch (servo based), I have come up with this design with the size needed for a Sony NEX and the adjust-ability to balance for any camera of that size or smaller to maintain roll balance.  Also, the base plate the camera sits on is deep enough to move the camera back to balance the weight on the pitch axis due to the size of the NEX lenses.  

Once I have hand crafted this design I'll post some video.  From there, if there is enough interest I may get a batch of these laser cut and put them up for sale.  Roughly $30 of 2mm CF board for this and whatever the rate is for laser cutting.

This specific design is for the LD-Power GM4008-57 motors which are 45mm in diameter, 21mm in depth and 85g each.  Still need to work out how many poles these motors have to be able to set up the firmware correctly.  If anyone knows please let me know?  I was planning on using the smaller LD-Power 2208 gimbal motor which was 39g or so but the eBay seller had the wrong picture and weight in the listing. 


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Just spent a couple of hours getting my head around the MultiWii V2.1 serial protocol.  This involved looking at EOSBandi's MW-WinGUI Visual Studio c# code and adapting the essential bits I need to a simple test VB 2010 app.  The app sends the commands to get the GPS bearing and distance to home as well as the Baro altitude.  The BT module connected to the Pairs MultiWii board sends back the info I requested and shows these values in textboxes on a basic form.

That's part one out of the way.

Next phase will be adapting that code, now that I understand how it is done, to Arduino code.

The code will output PWM on two digital ports to drive two servo's to position the patch antenna.  Rather than use the short range BT module I will set the MultiWii code to use 57600 rather than 115200 and hook up my XBee Pro module.  The other XBee will be connected to the Arduino tracker.  So the tracking Arduino will be asking the Hexacopter where it is and with any luck the Hexacopter will say "here I am".

If anyone is a VB programmer I can post the important bits here if they want to roll their own PC based MultiWii ground station.  Very easy to code once you know the binary protocol.

If I get the Arduino code happening in the next few days I'll post it here.

Also, if anyone is aware of an existing tracker for the MultiWii controller which uses the V2.1 protocol (not via OSD's fitted with GPS's and telemetry sent via audio) please let me know about it.  

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Time to try Hexacopters


Was getting annoyed by the stupidly heavy frame of the Scorpion Y650 which is made of thick fibreglass sheets (available from Hobbyking).  With the GoPro sitting on the camera gimbal and a 4S 3000mAh battery I was only getting 6-7 min flying time.  

Had a look at the price of CF sheets and CF 450 size heli tail booms and it looked like an affordable project to design and build a hexacopter from scratch.  Above is the basic design and below is the frame plates assembled with the CF booms and aluminium boom holders.


www.multiwiicopter.comin Queensland sell a clear dome with a 100mm diameter which will fit nicely over the electronics.


3689475686?profile=originalJust this portion of the frame is incredibly light.  I'm quite hopeful that I will get much longer flight times than the Y6 with this design.  Sheered one of the bolts in the process so will need to pull it all apart and try to get the remaining bolt out.


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PC joystick to 8ch Tx conversion

3689466544?profile=originalI've been looking at my unused twist grip joystick for a while now thinking about hooking it up to a transmitter via the PPM trainer port.

I might go a step beyond this and get a new 2.4GHz Tx module and add that to the joystick to make it a transmitter.

Fly-Dream make an affordable and reliable 2.4GHz DIY module with three pins for GND,+,PPM in.

I've been able to generate PPM from an Arduino in the past so now it's a matter of hooking the pots in the joystick to the analog pins and the buttons to the digital pins.  The pots move over a portion of the total travel in a joystick so my Vref will need to be a bit above the max voltage the pot will register.  So if the pot only travels between 0 to half way and I feed the pot +5v then the max output voltage will be 2.5V.  

I've also ordered an 8ch 12bit ADC I2C breakout which samples at about 12KHz.  This will give me more leg room at reading resolution of 4095.  The high resolution reading then goes through expo / trim / end point / sample filtering maths and comes out at a resolution of 1024 per channel.  As far as I can tell the PPM output resolution does not need to be any higher than that, nor do I think the timing in an Arduino can get any better than that.

The hat switch can be coded to move the camera tilt servo.  Might even pop out the digital hat switch and put a Wii joystick in there for tilt rate control.  

With the 8 or more buttons on the joystick I should be able to code it to give me all the PWM levels needed for channel 6 modes on the Arducopter.

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