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Garmin G3X Autopliot Auto Trim with Big Trim Motor

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Nov 23, 2013 9:13 am Post subject: Garmin G3X Autopliot Auto Trim with Big Trim Motor

At 09:50 AM 11/23/2013, you wrote:

 	  Quote: 	
		  Tim,



That's not quite the answer I was looking for.  But rather than try 

to figure out what's happening via text in emails, let's start w/ 

whatever diagrams you have.  Then we can drill deeper as necessary.



Standing by until you post the link ...


	


   The entire g3x manual is available at



http://tinyurl.com/l88273j



   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Nov 23, 2013 4:23 pm Post subject: Garmin G3X Autopliot Auto Trim with Big Trim Motor

At 02:47 PM 11/23/2013, you wrote:

 	  Quote: 	
		  

<tim(at)aircraftersllc.com>



let's try this.  HEre's a link:



http://www.aircraftersllc.com/docs/Garmin%20Suggestion.png


	


   Hmmmm  . . . you need to know the nature of Gramin's

   PWM philosophy.



   NORMALLY . . . pwm means applying a consistent voltage

   to a motor where duty cycle is adjusted to move the

   motor at any speed from zero to max.



   But in systems like the Beechjet (BIG motors with

   brakes on them) one cannot get slow, steady motion

   from the motor by fooling it into believing that

   the supply voltage has dropped. These systems accomplish

   precise control by PULSING the motor at full voltage

   with varying lengths of time.



   I did a study on Beechjets to characterize pitch

   trim performance at Mach cruise to see how short

   the pulses could be and STILL move the trim system

   but not so long as to be noticed by passengers and

   crew in the seat of their pants.



   Turns out 133 mS was the 'magic' number. If you're

   going to control your high current motor through

   relays, then you are most definitely limited to

   a full-voltage pulsed mode as opposed to the variable

   duty cycle so-motion mode.



   Question: Does the Garmin system really work in the

   PWM mode or PULSED mode?



   This can be done with relays . . . having very fast

   response times. This might be a case for installing

   the zener-based coil suppression. But the ideal

   buffer will be solid state. This raises the questions

   I cited earlier about prophylactic measures against

   unintended motion.





   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Nov 27, 2013 9:27 am Post subject: Garmin G3X Autopliot Auto Trim with Big Trim Motor

At 10:44 PM 11/26/2013, you wrote:

 	  Quote: 	
		  

<tim(at)aircraftersllc.com>


	


   Sure. Will this project include a wheel-master disconnect

   switch?



   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 04, 2013 2:42 pm Post subject: Garmin G3X Autopliot Auto Trim with Big Trim Motor

At 10:44 PM 11/26/2013, you wrote:

 	  Quote: 	
		  

<tim(at)aircraftersllc.com>



Any thoughts on using transistors in this setup instead of relays?



Thanks,



Tim



--------

Tim Farrell

Aircrafters

831-722-9141




	


    Tim, I thought I had responded to this. Are you

    still interested in a solid state 'relay deck' for

    this application?



    Do you plan to have a "stick master disconnect"

   switch?



   Bob . . .

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