Connecting a real flap handle

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Kaellis991
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Re: Connecting a real flap handle

#11 Post by Kaellis991 »

Joe,
I think I understand most of your description. When I get the unit I will need to do some drawings.
There is a good radio controlled model shop very near me. I’ll check into those servo horns.

Thanks,
Kirk

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jph
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Re: Connecting a real flap handle

#12 Post by jph »

Kirk, have a good look around in the rc model shop at the various stiff and also flexible linkages and also the push/pull rods like little bowden cables made from a plastic/ptfe outer tube and a thin metal inner, or somtines even a plastic inner. They will have all sorts of goodies. I fly RC when i get chance and have boxes of parts and linkages. Also have a look at the little ball joint links and control surface horns as the can be used to connect any moving hardware to pots and switches etc. Really useful when modding real hardware. They also sell the thin piano wire for link rods as well as threaded rod, really tiny, and screw on adjustable linkage end and ball joints for threaded rod. Great joy can be had. :mrgreen:
Joe. CISSP, MSc.

Kaellis991
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Re: Connecting a real flap handle

#13 Post by Kaellis991 »

That’s a good idea. I’m sure I can find the components that I can use.

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Sling
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Re: Connecting a real flap handle

#14 Post by Sling »

Some really good advice hear. Just like to add that you could probably still use a log pot if you can’t easily find a linear version. All you will do in the AM instrument is look for a small range of values around the individual flap positions to determine which notch you are in. This should still be possible even with a log pot. Linear is obviously better so this is just in case you have trouble sourcing one.

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jph
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Re: Connecting a real flap handle

#15 Post by jph »

Kaellis991 wrote: Mon May 23, 2022 10:54 pm That’s a good idea. I’m sure I can find the components that I can use.
Kirk,
Model shop owners tend to be great.
Definitively take a potentiometer and the arm and tell them that you want to link them together I bet they will pull all sorts of goodies out of the drawer and back room :D
They might have some really neat ideas also and they know all their stock.
As Sling says also, a log taper pot would also work in this case due to the coarseness of that range looked at. Luckily nowadays, unless you actually buy a dual potentiometer or specify log taper you would normally get linear. The reasons the dual pots tend to be log (logarithmic output) is simply because they are usually used in stereo volume controls.
Joe
Joe. CISSP, MSc.

Kaellis991
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Re: Connecting a real flap handle

#16 Post by Kaellis991 »

The idea of a string potentiometer is intriguing.

https://www.flaps2approach.com/journal/ ... while.html

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jph
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Re: Connecting a real flap handle

#17 Post by jph »

String pots are amazing, but freaking expensive if bought commercially.
Yes, you can make your own, but it would, for me, have to be a very specific use case where it was absolutely THE best option and no other would do the job. I have never (yet) ;) come across that situation.
Most of the time it is a case of looking how much precision you need Kirk. In this case for example, you need very very little and it wouldn't matter if there was even a lot of slop or play in the linkages of whatever solution you use. You will have a variation of around 200 steps of ADC per flap position :o .
Anything that needs real precision - as in flight controls - I would always try to use 'hall effect' sensors anyway. You can still get 'hall' pots etc, but it is fairly easy to make your own with a simple linear hall sensor IC (about 1 euro) and an appropriate magnet.
We are fortunate in design as we also do not need a linear response to all inputs as we have absolute control over the coding and interpretation of the inputs and what goes out or is actioned so any angular movement or non linear response due to arcs or levers etc is not an issue.
They are another 'string' to the bow so to speak .. pun intended.
Joe
Joe. CISSP, MSc.

Kaellis991
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Re: Connecting a real flap handle

#18 Post by Kaellis991 »

Good info Joe.
I am also thinking about using a lever and pot that came out of an old Saitek throttle quadrant.
It’s a 10k rotary pot.
When I get the handle next week I’ll see if there is some way I can repurpose this thing.

74BC483D-35BF-419B-92E8-479F72E0C055.jpeg

Kaellis991
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Re: Connecting a real flap handle

#19 Post by Kaellis991 »

Reusing that part from a old throtlle quadrant is a dead end. I found a way to create physical linkages between the flap handle arm and the pot.

Something I saw today though has me thinking about another possibility. I am wondering if it is even possible.
I opened up my Saitek trim wheel as I was looking for ways to integrate it with the flap handle since in the piper arrow they are mounted in tandem on the floor board between the seats.

I was expecting to see a rotary encoder or a pot, but I found that they used an infrared sensor on a PCB board along with a wheel that has holes around the perimeter.
The concept for using the sensor to detect the flap positions sounds very intriguing, but is that even possible to design?

I wouldn't know where to begin to design the electronics of such a PCB board. The physical layout of the operation I could design, but the electronic PCB is beyond me.
It would be an elegant solution, I think, but the electronics design seems to be all magic and smoke and mirrors.

Below is what I see in the trim wheel...the idea of using electronics instead of physical linkages has my curiosity peaked.
trimwheel.jpg

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jph
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Re: Connecting a real flap handle

#20 Post by jph »

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. CISSP, MSc.

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