How to Convert a real Cessna Altimeter for Sim use.

[737NUT]

Thanks and no hurry.
Les
P.S what did u use for the bottom bearing?.

I have several small flanged bearings saved from dismantling old instruments. I drilled a hole in the ply and pressed the bearing in. The flange sits on the ply and a brass tube rides on this. It keeps all the vertical movement out of the inner shaft. Servocity has them as well.

Rob

[737NUT]

Here is a copy of my code. I have the altimeter working as good as it can get using the cheap servo board. I would go with a digital servo for future versions.

Var 0022, name Altimeter, Link FSUIPC_IN, Offset $3324, Length 4
{
L1 = &Altimeter * -0.0533
L2 = L1 + 1010
&Altitudeservo = L2
}

Var 0023, name Altitudeservo, Link USB_SERVOS, Device 1, Output 2, PosL 100, PosC 555, PosR 1023

[iwik]

Thanks Rob,
I presume you have a collar on the inside of the ply base that rides against the bearing.
I must get some from Servo city at the same time as the rest of the stuff. Will get a flanged bearing at the same time. They really sting you for Int postage. Gears and the motor they want 42 bucks to send via post. Still if one needs it you just have to pay.Thanks also for the code.

Regards
Les

[737NUT]

Just a quick update, I ended up using a Pololu Jrk motor controller and got great results. Altimeter is still going strong and works great. It is with-in 20ft of sim altitude.
Rob

[iwik]

Hi Rob,
Thanks for the update,havent built mine yet but have all the parts. How are you I/f that to FSX as
before you had o/c servo card to drive it. Arnt these controllers serial input?.
Les

[737NUT]

Hi Rob,
Thanks for the update,havent built mine yet but have all the parts. How are you I/f that to FSX as
before you had o/c servo card to drive it. Arnt these controllers serial input?.
Les

Les,
The Jrk accepts, serial, analog, and servo signals. I use an OC servo card to drive mine. Rob

[AK Mongo]

Rob,

Happy Independence Day.

How does the pressure scale interact with the needles? Does turning it change the altitude like the real thing? If so, how do you provide the feedback loop to let fs know where it is set?

Reid

[iwik]

Rob,
Sorry for the reply, i only had a quick look at the specs and didnt see the r/c application.
I know you had accuracy problems with the salvaged card from an old servo but you thought a
digital one may be better. Did you try one before going to the jrk?. Previously i think you had problems with it returning to the same pos is this now ok?.
Thanks
Les

[737NUT]

Rob,

Happy Independence Day.

How does the pressure scale interact with the needles? Does turning it change the altitude like the real thing? If so, how do you provide the feedback loop to let fs know where it is set?

Reid

I just hit 'b' and then adjust my real baro adj on the altimeter. Not perfect but works for me.

[737NUT]

Rob,
Sorry for the reply, i only had a quick look at the specs and didnt see the r/c application.
I know you had accuracy problems with the salvaged card from an old servo but you thought a
digital one may be better. Did you try one before going to the jrk?. Previously i think you had problems with it returning to the same pos is this now ok?.
Thanks
Les

No worries I never tried a digital gutted servo as I had the JrK laying around. I do think a good digital servo would work as well, like the programmable Hitec ones.
Rob