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  1. #1
    150+ Forum Groupie BuzziBi's Avatar
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    Question Suggestions requested for the construction of compass.

    Almost done with the airspeed indicator and the brain starts to rotate around the next project.
    I want to try me on a the ADF instrument maby integrated in the compass.
    I see that Multi let me bring out the ADF frequency but do I need to think about the direction of the neadle?
    If I just leave it pointing straight ahead in the flight path, I will lose the possibility of bearing on frequencies in other directions?
    Or how is this supposed to work?
    Do I use the AFD frequency in combination with other values​​?
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  2. #2
    75+ Posting Member vikingsraven's Avatar
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    Re: Suggestions requested for the construction of compass.

    im working on a magnetic compass at the moment , using a stepper motor, im sort of half way through the code pm me! and we can work on this together, then publish it on here.
    have a look at this
    http://www.thaitechnics.com/nav/adf.html

  3. #3
    150+ Forum Groupie BuzziBi's Avatar
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    Re: Suggestions requested for the construction of compass.

    I took a look at the page, have studied something similar. I then started to test Multi with ADF ticked. The way I see it, one only gets feedback on ADF frequency from Multi, no data say in which direction (relative to the plane) where the transmitter is located. Is there anything I overlooks?
    Life was hard, but then came Windows 7.
    Now we can fly! --------
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  4. #4
    75+ Posting Member vikingsraven's Avatar
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    Re: Suggestions requested for the construction of compass.

    yeah theres no bearing info from adf, maybe we should ask jim nicely as hes about to tweak his code at add it!

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    150+ Forum Groupie BuzziBi's Avatar
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    Re: Suggestions requested for the construction of compass.

    vikingsraven
    Have had a little mind game today.
    Take a look at the picture.
    10-01-2014 19-17-29.jpg
    This I think is doable!
    Found incidentally some nice pages here!

    EDIT_ Have you found a solution to the positioning of the stepper motor to the compass?
    Last edited by BuzziBi; 01-10-2014 at 03:11 PM. Reason: Edit
    Life was hard, but then came Windows 7.
    Now we can fly! --------
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  7. #6
    300+ Forum Addict Tom_G_2010's Avatar
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    Re: Suggestions requested for the construction of compass.

    I had to put my build on hold in the spring of last year, but I am dusting it off now and getting busy again. When I stopped I was part way through coding my whiskey compass. I purchased a high res stepper motor (0.9 degrees per step) and an optical sensor.

    My plan is to use a 10 to 1 worm gear to get the highest possible resolution. To initially position the compass when an aircraft is loaded I am writing code that will activate the stepper and rotate it until the optical sensor triggers through a pinhole in a disc at a predetermined position like 0 degrees It would then advance to whatever heading was being sent from Link2FS.

    I'm not sure yet how to handle ongoing calibration. If someone made a stepper with 1 degree or 0.5 degree steps it would be so much simpler. But with 0.9 degree steps, even with a 10 to 1 ratio, there will always be some amount of error introduced with each movement. I was pondering a couple ideas like a calibration check any time the heading happens to cross North. But that might not happen to often in a long distance flight headed south.

    The other idea I had was to put optical sensors more frequently around the compass like at 0, 90, 180, 270. However that gets mechanically complicated and I need a way to distinguish each position for the calibration to be functional.

    Tom G.
    https://www.facebook.com/mycessnasim PC: Intel Core i7 Haswell @ 3.8GHz, 8Gb Ram, Win 7 64Bit, dual SSDs, GeFroce 780 SIM: FSX w/Aclrtn Pk, FSUIPC4, ASN, UTX, GEX, REX 4

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  9. #7
    75+ Posting Member vikingsraven's Avatar
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    Re: Suggestions requested for the construction of compass.

    BuzziBi thanks for the link.
    Tom
    been looking into the error problem, maybe i have a solution, 0.9 degrees is fine.
    You can fix the error in the code.
    eg.
    using modulo you can work out the difference and add extra pulses to compensate.
    Code:
    addstep = reading % 9;   // its 9 as we know 10 steps is going to be 9 degrees and it gives a whole number to play with.
    this does the following:
    for example original heading - new heading ; 200 - 189 = 11;
    11%9 = 2, as 11 x 0.9 = 9.9 if we add 1.8 ( 2 steps) it gives us 11.7.
    example 180 -187 = 7
    -7%9 = 7 (6.3) 7-6.3 = 0.7

    As most of the compass roses are in 5 degree steps this isnt going to show up, but over time this will increase, so if we put the .7 into an accumulator variable, and to it or subtract ( if we head back to the original position) then when it gets to 0.9 we can also step either forward or back to compensate.

    now the major problem really is the step form 359-0 and 0 to 350;
    this will need an extra bit of code

    Code:
    if (previous >270 && new <90){
     previous = 360 - previous;}
    else if (previous <90 && new >270){
    new= 360 + new}
    you can actually get a micro stepper drive as well this can increase the resolution X 8 , you can still use the formula to compensate for that error as well.
    Mark

  10. #8
    150+ Forum Groupie BuzziBi's Avatar
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    Re: Suggestions requested for the construction of compass.

    A thought!
    Can you use a cheap OPTICAL MOUSE SENSOR to calculate how far the "compass rose" (it's what I call it ) has moved?
    If you only use one axis to calculate the movement of the compass can we use this information to correct the deviation in degrees stepper motor is running? Or maybe use a standard 5V motor?
    In any case, a fun thought for use in any connection with simulator!


    http://www.martijnthe.nl/2009/07/int...-your-arduino/
    Life was hard, but then came Windows 7.
    Now we can fly! --------
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  11. #9
    75+ Posting Member vikingsraven's Avatar
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    Re: Suggestions requested for the construction of compass.

    yeah i suppose you could, all i was going to do was just keep track of the counts after a zero point (N) and let the duino do the work, theres a really cheap optical sensor called and LED! they were originally designed to be photodiodes but some one wired it up wrong and they produced light so they became LED!
    you can put on facing the other and read the light level.
    http://playground.arduino.cc/Learning/LEDSensor
    cheap and plentyfull
    actually just ripped a hp printer apart and it doesnt have steppers in it( annoyingly ) but does have a motor with i think( im not counting them) 4096 optical disc on it.
    the optical mouse is basically a low res camera, 20 x 20 pixels i think so maybe some possibilities in that!

  12. #10
    300+ Forum Addict Tom_G_2010's Avatar
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    Re: Suggestions requested for the construction of compass.

    Vikingsraven,


    Thanks, I'll experiment with that this weekend.

    Here's what I did in my original code to convert the .9 to match the 360 using the "map" function.

    When looking at the 4000 value below keep in mind my stepper motor is a 0.9 degree 400 step and I will be using a 10 to 1 worm gear arrangement.

    Code:
    HeadingVal = map(HeadingVal, 0, 359, 1, 4000); //Convert 360 degree heading value to 400 steps
    And, for crossing north I did the following.

    In the code below StepMaxP = 1000 and StepMaxN = -1000 which was arrived at by experimentation and seemed to work well.

    Code:
     StepVal = HeadingVal - HeadingVal_Last; //Calculate difference between last heading read and current heading
    
           if(StepVal > StepMaxP){ // Adjust for crossing North
              StepVal = -1*(4000 - StepVal)-10;
            }
    
    
            if(StepVal < StepMaxN){ // Adjust for crossing North
              StepVal = -1*(-4000 - StepVal)+10;
            }
    https://www.facebook.com/mycessnasim PC: Intel Core i7 Haswell @ 3.8GHz, 8Gb Ram, Win 7 64Bit, dual SSDs, GeFroce 780 SIM: FSX w/Aclrtn Pk, FSUIPC4, ASN, UTX, GEX, REX 4

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