DC motor Autothrottle

[OmniAtlas]

This thread is 7 years old but still pertinent today.

Cheers - I am still trying to decide if I should use a phidget or OC DF motorcard for my trim wheel. I would be open to suggestions, thanks.

[brianwilliamson]

2 ways you can get the position of the Trimwheel.
One ito use an ordinary pot and gear it as in this pic:



Or connect a multi turn pot direct or geared. (10 turns I think)

The 12 volt motors that are geared down to very low rpm are strong enough to break your arm !! So you do not need a 10hp. motor.


I use an ordinary pot and geared as in in the pic. using IO DC Motor card, which handles it without any hassle at all.

Not sure if this will help as I guess it depends on the room you have to install all this.


............Brian W.

[OmniAtlas]

Hi Brian, I must have been confused because I did not know the pot had to have a physical connection to the trim wheel. I was under the impression the motor card does some voodoo magic with the pot and is able to position sense.

I checked on the throttle shaft and it seems it turns 6 times from negative to positive trim.

Do you need the OC motor plus card or will the regular version do?

Unfortunately I do not have the expertise to build a pot into a trim wheel.

[brianwilliamson]

Ok a quick setup of how it works:

The trim wheel as you have indicated does 6 revolutions from full forward to full aft. The sofware and the DCMotor card need to know where the trim wheel is exactly.


So you connect a potentiometer to the trim wheel physically and connect the 3 wires from the pot., to the card.



The card then tells the DCMotor board to move the trim wheel with the 12volt motor to wherever the potentiometer needs to be.

The software does all the work, as it reads the pot.... and if it does not match where the aircraft says the trim should be, it then turns the motor in that direction.

As I said it depends how you can connect the Pot., but there should be one already connected to the trim wheel, as the real aircraft works in exactly the same way.


Hope I explained that a bit better. I am about to pull my throttle and trim out as I only have 4 turns on my setup, so need to rebuild.


Cheers................Brian

PS......Ordinary one is ok, but later one maybe more reliable

[OmniAtlas]

Hi Brian,

I've checked my pedestal and I don't think there are any connections from the trim wheel to the pots in the unit -- in the TCU (throttle control unit), where the pots sit, only the levers are connected. I will keep on experimenting, otherwise I will try and imagine how I can construct a mechanism to house the pot and dc motor.

I would like to connect the DC motor directly to the shaft seen here --

[brianwilliamson]

I should perhaps have added that you may connect the pot., to either the trim wheel or the trim indicator.

Both do the same job except the indicator does only turn a fraction of a revolution whereas the trim wheel does 6 revolutions.



Cheers.................Brian W.