MobiFlight Community Support

hello captains, i am having some trouble with steep motor 28byj-48 in a Analogic altimeter ..i am build some one using some gears relation, the works fine, until reach 16.000, where the stepper motor stop and moves back in a wrong direction...i testet in a couple of aircrafts, FSUIPC 3324 4 bits.......multiply $*-1 to correct the direction.....Sim/steeper.....1000/2048...if some one had the same , please help me....thanks..

Hi Souza,

I will have a look at it and let you know.

Can Confirm THIS,

The Value from FSUIPC is working correct !

Just take a minute to think about why this happens at straight 16.000...
A Turnback normaly is a sign for a Outrunning byte ( Like the 32768 Altitude Problem in the PMDG MCP Display) This happens if we use Signed and Unsigned in wrong way for example, or if value reaches the limit of the Bytes. BUT straight 16000 is not a problematic value!

But i think i know the problem now.....

16.000 Feet is in a 1000ft per circle exact 16 full turns in one direction.....
Youre stepper got 2048 Steps ...... 2048*16=32768 And THIS is exact the Maximum Value of a 16 bit Signed Word ... (-32768 to +32767)

So i would say.... Sebastian send the Position to the ULN2003 with a Signed Word .... Using Unsigned is maby not recommend cause we need sometimes Steppers that show negative values, too. ( this would increase the limt to 32 Turns but already not enough if you fly higher then 32.000 feet.

I don´t know the struckture and if the limit is in the ULN Board itself But using a Dword (32bit) will increase the limit from 16 turns to over 1 Million.

Let´s wait for a responding from Sebastian again.

Additiona Infos....

If Sebastian can fix this in next release everything is fine....
If this is a bigger Problem (hardcoded) or if you need immediate Help NOW you can use a gearbox to solve this.

Maby a 1:4 Cogwheel system should work..... Means.... 1 Turn of Stepper result in 4 Turns of Gauge.

So you just neet to use Transform, Interpolation or the Sim/Stepper entrys to set this new system....
If Value increase by 1000 ft youre Stepper should not turn 360° . Now it should only turn 90°.
With this mecahnic we push the Limit from 16000ft to 64000ft. Much more then a normal aircraft can reach .

hello Pizman82...i dont understand a lot of how MF work, i am a new home made cockpit builder, i know that using a gearbox solve but, these system was working on limit, the tork from stepper motor is to low, the gears are made aluminun, it was a chalenge to find who can was able to do is, beause the teeth is too small, and some times a minor blocking is sufficient to steeper lose the position and pass the wrong altitude, and i believe that plus another gear box could me gove another problem, good explanation about the value signed word FSUIPC, thanks,to me if Sebastian solve this, is great, i wait....please, check my YOTUBE chanel to look working...
https://youtu.be/K6meM8TVngk

Hi guys,

I had it right (long, 32-bit) in all places - but one!
Thanks for finding this! It will be fixed with the next release (this weekend)

Oh Nice. So Problem is solved with next release......

@ souza....

Hope you not missunderstood what i mean. You NOT should change cogwheels inside the motor or manipulate the prebuild gear system....
You can buy verry cheap Cogwheel sets on ebay for example (Plastic)..... Then you build a box, behind youre panel....
The Shaft of the Motor NOT go to the Needle of youre gauge (like now) it´s just mounted with a cogwheel and fixed on maby a pice of wood. then This cogwheel is compined with another smaller wheel ( 1/4 of teehts) and THIS one is mounted to a longer shaft that can turn free.... And now you bring this new shaft in the gauge and make youre needle on it.
Just a simply 2 Wheel Gear external of your Motor.... Between Stepper and Gauge Shaft.

I not found good videos but maby this one helps you a bit... https://www.youtube.com/watch?v=BY0IALNXCSA
I know our motors are much smaller but the basic system is the same here.

But finaly this work.... That was just information if you need somewhere else a gearbox !

I had trouble with the Webserver and was not able to release during the last weekend.
Stay tuned - update established on the localizer...

I just released 7.3.0

gentleman....i instaled the new version 7.3.0 and tested the altimeter climbing to 25000 FT and work fine....thank you DOCMOEBIUZ and PIZMAN82 to solve these and your attention...for me is solved.