Connecting a real flap handle

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Kaellis991
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Re: Connecting a real flap handle

#21 Post by Kaellis991 »

jph wrote: Sun Jun 05, 2022 4:15 pm Hi Karl,
Not a good idea unfortunately as you need an 'absolute' reference for flaps and this is an 'incremental' reference.
The saitek has no idea 'where' it is, it only tells the sim if it is trimming one way or the other.

It is, in effect, offering a very similar output as you would get from an encoder, which incidentally is the best way to implement trim wheels if you are using a motorised trim / autopilot driven trim.

The flaps need to know exactly where they are at any time so a potentiometer is perfect. Small microswitches will work but I would always use a potentiometer for flaps. Nice and simple.
Joe
Joe,
There you go stomping on my dreams again.... ;)
But it does make sense.
Are you saying that infrared sensors cant be designed into a board to determine an absolute position?

I used momentary micro switches on my fuel selector that turned out very well. So I thought about that idea for a while but the geometry of the flap handle and bracket better lends itself to potentiometers and mechanical linkages.

Edit; Infrared sensors can detect an on or off state... correct? Similar to the door protection in my garage door opener... Either the light gets though to the receiver or it doesnt...
After looking at those typical IR proximity sensors It seems possible to use four of them, each of which would turn on when the flaps are changed to each of the four positions. A part of the flap lever or an add-on component could activate the proximity mode when if rotates into the field of the sensor....I am just spit ballin' here.
Kirk

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jph
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Re: Connecting a real flap handle

#22 Post by jph »

Hi Kirk,
It is always possible to do something with many different forms of tech.
Yes, absolutely, you could use a quantity of sensors and a card with various 'holes' in for light to pass and detect absolute positions in definite steps - not on a continuously variable rotation though. That could only ever be pseudo absolute in respect of relative to a start position, which is not absolute... absolute you can think of as being able to be determined at power on. Using multiple sensors you could detect many positions. For example, 4 sensors could detect 16 positions using binary patterns etc. The world is your crab, or was it oyster ?..

Something that moves from a start to a finish without overlapping is ideal for absolute. Something that rotates past it's starting point CAN be made absolute if the maximum number of rotations are small - ie your trim, as you can use a pot either with gearing or multiturn. This IS then absolute.
However, just to really piss on the chips :lol: This is not a good idea for a trim if autopilot is involved as you end up in a vicious fight with handbags at dawn.
You move the trim wheel, the adc reading is the trim position. This is sent to the sim. The sim now engages autopilot... the trim is being varied by the AP now. When AP is disengaged the sim looks back at your trim wheel (this is presuming it is not a powered trim) and sees wherever it was prior to AP being engaged.. the aircraft now - most likely - sees a massive difference in its current trim to the commanded trim from the hardware trim wheel pot, craps itself and you get a replay of the 737 MAX :shock:

Now you can probably see why the saitek uses an incremental / relative positional sensing and not a pot as too many sim pilots have simulated houses getting very large very quickly and then played the new type of MSFS which is the new MS Funeral Simulator with the 'PDMG' add on (Please Dig My Grave)...
;)

Definitely horses for courses.

Joe
Joe. CISSP, MSc.

Kaellis991
Posts: 581
Joined: Mon Sep 07, 2020 8:49 am

Re: Connecting a real flap handle

#23 Post by Kaellis991 »

Joe,

So for those autopilots in the big iron sims, what types of trim hardware is typically used for the airline crowd in MSFS?
There are aircraft that have altitude hold and subsequently the autopilot will have to adjust the trim to maintain target altitude.
Since I am designing a cockpit with an autopilot that does not have the altitude hold option, I will have no issue with that.

What is the typical way? Rotary encoder or pot? Are you saying that the Saitek with it's relative positional sensing should not be used with an autopilot having altitude hold?
In other words, those MSFS big iron simmers need to use something other than the Saitek product?

The Flight Velocity trim wheel uses either a rotary encoder or a potentiometer. I can't tell from just looking inside the box.

I saw a video for a DIY trim wheel using mobiflight and a rotary encoder. Is that the way the mobiflight MSFS crowd does it typically...with the encoders?
I definitely understand now about the relative positions method afforded by the Saitek trim wheel.

Kirk

Kaellis991
Posts: 581
Joined: Mon Sep 07, 2020 8:49 am

Re: Connecting a real flap handle

#24 Post by Kaellis991 »

jph wrote: Sun Jun 05, 2022 5:43 pm
Now you can probably see why the saitek uses an incremental / relative positional sensing and not a pot as too many sim pilots have simulated houses getting very large very quickly and then played the new type of MSFS which is the new MS Funeral Simulator with the 'PDMG' add on (Please Dig My Grave)...
;)

Definitely horses for courses.

Joe
Taking flight simming to a whole other level of realism....

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jph
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Re: Connecting a real flap handle

#25 Post by jph »

Hey Kirk, will be out for the rest of the evening but a quick reply.

Saitek is fine with AP as it can remain still when A P trims and your code simply redefines the current hardware position of the encoder count to be equal to the internal sim trim position on AP disconnect. That is not wise to try do with a pot as you end up fudging an absolute plus or minus offset after every trim button or AP usage and you lose relative position to the end stops. Very very messy.

Motorised trim, (if done correctly) , no matter if GA or Commercial / Heavy normally uses three components, preferably 4, a stepper or dc drive for the trim wheel(s), an encoder DRIVEN by the trjm wheel and a servo to drive the indicator pointer. Fairly simple really. It is also appropriate and a nice touch to add a 4th component, a feedback potentiometer, that is driven by the indicator servo so that you now have a useful reference that IS absolute and which is also really neat at startup to reinforce good trim habits as you will now start the sim, should you chose to implement it, where you left off which is entertaining if you are not cleaning up the mess after a flaps 40 1700 rpm 'tactical approach' nose dive in an old 172M ! :shock: or a low and slow nose high power on short field where the yoke was in the belly button :lol: .

Joe
Joe. CISSP, MSc.

Kaellis991
Posts: 581
Joined: Mon Sep 07, 2020 8:49 am

Re: Connecting a real flap handle

#26 Post by Kaellis991 »

For those that may have a smidgen of interest, I have an update on my home cockpit flap handle build.
With Keith's work in writing the LUA script for the AM hardware, I was able to get these infrared sensors to work with the flap lever.

IMG_4346 3.jpg

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