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Posts: 2
Hi there

i have been working on a IAS Gauge from a real plane. i striped the guts and 3d printed and made it for a Stepper Motor

my problem is that the range is setup from 0 to 750 knots but when i load up xplane and fly its off by a lot, ive no idea how to tell mobiflight where its sure post to be

heres a picture as you may notic that from 0 to 10 its so small then the rest of the way its fine

2020-01-22 10:12
From: EDDG, Germany
Posts: 1522
Hi Andy!

Welcome to MobiFlight!

May it be that you have two scales on the instrument?
The outer one from 80 to 400 and the inner one from 350 to 750?

So speeds below 80kts are not relevant for the instrument and between 350 and 400 you need a point to switch from the outer one to the inner, right?

The you need two configurations. One for the outer scale and one for the inner. You have to define for the outer scale (350-400), when you switch to the config of the inner one and you have to define for the inner scale the point where the config switches from inner to outer scale (400-350).

These switching point can be set in the preconditions of everey config.
2020-01-22 12:21
From: ETSI, Germany
Posts: 3521

I not see a gauge like this before.... But i think he not need 2 Configs.

This is a "Non linear" Gauge with a Turning range of maby 610-620°
I can not see it on the picture but it looks like the Outer gauge is linear..... also the inner gauge is linear.... but both are different..... So we must see the WHOLE Gauge as NON Linear.

If i understand right then the complete gauge can be done with a accurate and good INTERPOLATION.

To do this you need at first do know the important things.

1: What format got the raw Data from your Sim..... You read a Offset... Tell us how "speed" looks like.
Full Numbners or a decimal value. Clear Numbers or recalculated by a formula.
1:1 Knots like 0-750 or reduced like in your gaug e.g. 0-75

2. Stepper Settings. Is your Stepper a 2048 Standard Stepper or do you use a 1024 or 4096 Stepper ?
( Symply find out by testing)

Finaly with this informations you can set a Interpolation.
For example it start at.... SIm 80 Knots = Gauge Zero Position ..... SIM 400 knots = Gauge 40 Position ..... SIM 750 Position = Inner Gauge 75 Position
If i´m right and both ( inner and outer) are linear for itself then this 3 values are enough to run the gauge perfectly.

Please report experience or request if you need more help !
Good Luck !
2020-01-22 17:34
Posts: 2
hi thanks for the replies,

its an old millity aircraft gauge, it was never digital,

so im using x plane, and i dont know what type it is, i know its a 28byj-48

the display settings are set to SIM/STEPPER = 1000/1680 and if i test value 1010 its does 360 degrees,

1680 is from 80 to 750 knots not sure if thats how it works, im new to flight sim projects, my plan is to build a full size boeing cockpit in the shed i have my racing sim cockpit, im a full time hobbist i was a mechanic but due to kidney failure and my transplant op going so well (5 month post transplant so far) im 26 and doing well, anyway ive been doing alot with electronics more and more i know alot about coding but this is a new area for me,

anyway im going off track, so in the FSUIPC tab the offset is 0x02BC byte size of 4 and transform of $/128 not sure if any of this make sence to you guys.

in interpolation i have input set as follows

in / out

80 / 0
400 / 890
750 / 1680

but the gauge is still off, is there something im doing wrong

2020-01-23 05:05
From: ETSI, Germany
Posts: 3521
Hi Again

Your values makes no real sense......
You say Sim / Stepper is 1000/1680 ....... You say a Test Value of 1000 will turn gauge by 360° ..... In next line you say 1680 is from 80 to 750
That all not make any sense..... A Stepper normaly use for 360° 1024, 2048 or 4096 steps..... So i can not belive yours do 360° with 1680 steps.

Also you said 1680 is from 80 to 750 knts..... You know gauge must turn nearly 600° to show this area ? After starting point ( 80Kts ) it turn maby 330° and reach outer scale 400kt.
Then it must turn "over" and now the inner scale is used and it turn another nearly 270° to the 750kt point.

At first find out resolution of your Motor.

Please use SIM 1000 / Stepper 2048 TEST Value 1000 and press TEST.
If servo turn exactly 360° it is a 2048 Stepper ..... If it turn only 180° it is a 4096er Stepper...... If it turn 720° TWO Full circles it is a 1024 Stepper.

Then i recommend to use the 360° Methode for the Interpolation
Use as Settings SIM 3600 Stepper xxxxx ( The Steps you find out before.... Mostly 2048)
As Zero Point i would use the 80kt Position OR if you like the needle should be on the green dot on the bottom then set it there.

NOW you need the TEST Funtion of Mobiflight and maby a Geometric triangle or good eys.... You must find out the Degrees from Zero Point to the needed calibration points in the gauge..... For example the angle from Zero Point to the 400kt Outer scale Mark ( Maby 320° )
320° means in our scale a value of 3200 ( Cause we use 3600 for a full circle) ....
So use TEST Value 3200 and run TEST..... If Needle stop exactly at 400kt (Outer scale) then its fine. If not you maby must increase/ decrease the value a bit and test again.... Until you got the needed value.
For the 750kt Points the value is "above" 1 Circle so its above 3600 cause the needle must turn more then 360°
From short view i would say its maby 600° .... So Try out Test Value 6000.
Find out that point, too.

Then all is like explane above.... Try if this 3 Points (80,400,750) are enough vor a correct gauge.... If NOT then you must maby also find the 200 and 550 Point to have more coordinates.
Like you still do use interpolation (enable mark) and define for 80,400 and 750 knots "raw value" the corespondending Values you find out by testing before.

Important to understand.... All Positions above 450kt ( or a bit less whatever you set Zero Point at 80 or at green dot) are MORE then 360° ..... So for calculate this point you must always remember that gauge must make a full circle before.
[Last edited by pizman82, 2020-01-23 14:00]
Good Luck !
2020-01-23 13:10