BMS stick trim pitch problem

[bluc69]

I have installed the Trim Panel that now works with AIC pcb (thanks Arend!!).
Everything on the panel work correctly: as I rotate the three pots the plane trim as expected.

The problem is when I use the Hotas Stick trim: while the roll trim works correctly overriding the Trim Panel roll pot control, the pitch doesn't work.
If I move the hotas hat up or down the trim tries to move but then it seems that the pitch pot position takes the control and reset the trim.
I have disabled the pitch pot in the BMS setup and the stick regains its function.

Could someone tells me if this is a BMS bug or if I'm doing something wrong?

[bluc69]

UPDATE:
After some test I discovered it isn't a Trim problem as all the Trims work correctly.
It's just a problem with the needle that, for some reason, resets to the middle.

I have the same problem on AIC panel and on 3d cockpit...

[Cupra]

You used the switch on the panel to select disc trim?

[JJ]

Do you use XKEYS for the hatswitch on the SSC ??

[bluc69]

Solved!
It was just a problem with the pot's dead zone.

[Falcas]

Hi,

If you use pots on the trim panel and actually use them in BMS as well, the axis will always overrule any other trim input. So as you said, you can use a large dead zone for the axis and never use the pods. IRL you will hardly (never) use these anyway, as you always use the hat switch. (its a pilot thing  )
The other option, which I use, is not using a pot but rotary encoders. This way you can use both at the same time.

Gr Falcas

[Nikolas_A]

The best option IMHO is to make it work like the real thing. Use motorized pots, and make the stick hat operate the motors. Then read the pots in BMS

[MrWell]

I'm in doubt with this too. Could motopots be operated manually too? and how can you control the motors with the stick clicks?.
Thanks!

[Rufus]

Henkie turned me on to these - you want the linear ones:

http://www.ebay.com/itm/ALPS-dual-motorized-rotary-Potentiometer-RK16812MG-10K-o-100K-log-o-linear-pot/351075505733?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222006%26algo%3DSIC.FITP%26ao%3D1%26asc%3D22853%26meid%3D7061857290723519302%26pid%3D100011%26prg%3D9833%26rk%3D1%26rkt%3D10%26sd%3D350815232018

[MrWell]

Thanks Rufus,
I read Henkie thread and I had these motor pots located but I don´t understand the way the stick operates the motor.
Do you use pokeys (or other one) and when it receives an input from the stick trim it sends...what?.  I don't know how to make pokeys to operate a motor... 

[Rufus]

Yes - I'm planning to use Pokeys, but I haven't gotten to that point in my build yet.  What you'd need to do is write a macro in the Pokeys that will not only output the keystroke for the proper Trim input to the sim, but also activate the proper digital output pin at the same time.  At least that's what I'm thinking about doing - Pokeys has digital output pins and all you need do is determine if the motor needs to be run up or down and let a pin provide that output.  Looking at the spec for the pot's motor it looks like you may be able to do that directly from the Pokeys digital out pin, if it will supply 5 VDC.

Another one of the nice things about these pots is they are stereo...two channels - so you can use one channel for control and one for feedback. 
Then one of the channels on the pot can be fed to an analog input of the Pokeys and calibrated to the Trim position, and the other used to insure the pot position matches...or something like that - I'm still thinking... ...

[MrWell]

OK, I think I got it. I didn't know outputs in HiGH could move a motor then I understand that one could move one way little by little and another to the other way but I'd rather use a Darlington transistor to supply the motor like with leds (ULN2803a).

Now, I know how to use a pot to control but I not very sure about the feedback one... thinking too 

I am not on the construction of that panel either but I like to have all PCBs and schematics before or at least know how it should be

Thanks for the help! 

[MrWell]

By the way, half the price  :

http://www.ebay.com/itm/2x-Motorpoti-2x-10-KOhm-lin-Getriebemotor-Modellbau-/291141317919?pt=Motoren_Getriebe&hash=item43c95ff51f

[Red Dog]

IRL you will hardly (never) use these anyway, as you always use the hat switch. (its a pilot thing  )

that's strange because my personnal experience is different
i hardly use the stick trims in bms and i always use the wheels on the mantrim
although irl, i do use the stick trim

[Nikolas_A]

What you'd need to do is write a macro in the Pokeys that will not only output the keystroke for the proper Trim input to the sim, but also activate the proper digital output pin at the same time.

Not a good idea. In my opinion you should not send keystrokes from HOTAS to BMS. Only the analog value of the pot. So it's either:

HOTAS trim -> motorized pot -> BMS

or

manually operating the pot -> BMS

If you send both keystrokes and analog values to BMS on will override the other

[Rufus]

What you'd need to do is write a macro in the Pokeys that will not only output the keystroke for the proper Trim input to the sim, but also activate the proper digital output pin at the same time.

Not a good idea. In my opinion you should not send keystrokes from HOTAS to BMS. Only the analog value of the pot. So it's either:

HOTAS trim -> motorized pot -> BMS

or

manually operating the pot -> BMS

If you send both keystrokes and analog values to BMS on will override the other

That's not really what I'm saying to do - the Trim hat has to make two things happen: 1) send the key for Trim when actuated as it is usually activated in "clicks" of Trim; 2) move the Manual Trim motor and provide an analog Trim input.  What needs to happen is for either the pot or the hat to supply the Trim input, so those inputs also need to be made mutually exclusive.

The end goal is to be able to simulate/replicate a failure of the Trim hat input - like getting shot up, having some sort of FCC failure, and being forced to use the Manual Trim wheels.  I'm assuming that in this case the sim will ignore the hat input...hence my thinking that I also need a feedback loop on the pot position to make sure it matches the last driven position of the stick input.

It may prove simpler than this...if there are actually two inputs - one for MAN and one for HOTAS.  But I likely still need to insure they are synched somehow.

[Road218]

The best option IMHO is to make it work like the real thing. Use motorized pots, and make the stick hat operate the motors. Then read the pots in BMS

@Nikolas
Your solution is simply perfect. Just like any real aircraft; you have manual pitch trim and if you are luckly you have a electric motor driving the trim from the flight yoke or stick with a disconnect switch to disable it in the event of a failed switch causing a run away trim up or down condition. Just like the real F-16. GREAT input!

[Rufus]

The real Manual Trim panel has servos connected to the Roll and Pitch wheels which move the wheels when the Trim hat is actuated - selecting DISC on the MANUAL TRIM panel both disengages those servos (which also incorporate a slip clutch), and disengages/locks out the Autopilot....the Trim wheels also have mechanical stops.  That's how the jet works and that's how I want my setup to work...I just have to figure out how to do it...

Somewhere around here someone had posted pics of the guts of a real one and I didn't grab them...I'll see if I can find that post and add a pointer.

[Red Dog]

lacking the motorized pot, here 's what is relatively easy to do
<a href="http://www.youtube.com/watch?v=LTOUfw1cpd4" target="_blank">http://www.youtube.com/watch?v=LTOUfw1cpd4</a>
it would have been neat to have the knobs moving along but honestly i didn't find it worth to invest in motorized pots 

[Rufus]

Been thinking a bit more on this and had a look at the Dash 1 - in Figure 1-47 it says about the TRIM/AP DISC switch -

"Deenergizes stick TRIM button, prevents autopilot engagement and ATF/autopilot blending, and deactivates trim motors (manual trim wheels still operative)"

So this is what we are trying to implement if we want it work the way the jet does - the MAN TRIM panel and the stick need to retain distinct function, but mirror each other in position.  The assumption is that if the sim invokes an FCC failure that fails the hat the Trim hat (key) input will be ignored, the motors won't move, and then you will have to use the wheels - so you need to be able to get the Trim inputs from the pots...and maybe only the pots; I could use another non-Trim associated key for the hat to to drive the motor signal I suppose.  But that probably won't play with what the sim expects as far as failing the hat goes.

Since I'm going to use motor pots what I'm planning to do is mechanically connect the Trim position indicators to my pots/wheels seeing as they both move at the same time no matter how the Trim signal is commanded and if the hat is failed they don't move at all. 

But after reading the Dash 1 I'm thinking that the only reason a pilot would use the DISC switch is if the autopilot has the control surfaces stuck, and also thinking that the TRIM/AP DISC switch needs to do a couple of things if you are using motor pots and want your panel to work like the actual aircraft - 1) interrupt the circuit for actuating the pot motors; and 2) send switch state to the sim so the sim can cancel/inhibit the Autopilot.

In the ideal case you'd want to use a TPTT switch...I think.  With a DPDT switch you can interrupt the motor circuit for each pot, but I can't see how you'd also matrix the switch state since the two poles would be carrying voltage.  I hope I haven't bought a TW series switch for this one yet...I need to consider my solution in further detail first.

[henkie]

I must re-read this when I am not tired.
As far as I understand, my solution will work. It is just a matter of software, so I'm flexible 
(my approach can be read on my website).

- Henk

[Rufus]

You're the one that started me down this road, Henkie - I trust ya... !

I also re discovered this input to me from Nigel -

http://www.viperpits.org/smf/index.php?topic=8750.msg113966#msg113966