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  #1  
Old 02-14-2018, 01:56 AM
akschu's Avatar
akschu akschu is offline
 
Join Date: May 2008
Location: Houston, Alaska
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Default Thoughts on something I'm working on (Aviation friendly arduino board)

So I have a need to have two servos (not an RV) reach run an elevator trim tab and thus it's pretty important that they don't get too far out of sync with each other, so I started working on a little arduino compatible board that uses standard DB25 and DB9 connectors and high quality components with integrated motor drivers so that I can drive each servo and poll the position. I also added a digital pot, so I can report the trim system position back to the EFIS.

This solution should be more reliable than a relay deck because the motor drivers are designed to handle inductive loads and not fry contacts, and because it's completely solid state.

I decided to go ahead and design the board for more generic use, and have the following:

2 motor drivers
2 channel digital pot
6 analog inputs or digital inputs/outputs
6 digital inputs/outputs

This offers the builder the ability, with a little code, to do cool things, like hook up a rotary encoder to two pins and have a manual trim wheel for digital trim. Or you can protect against run away trim by hitting any other button to override. Or you can drive an RC servo for heater controls with a pot on the panel. Or you can design a simple wig-wag lighting system and use the motor drivers to drive that. Or you can sample a sensor and indicate a fault LED. Or you can have a neutral trim button, which drives the trim servo(s) to neutral when pressed. Or you can slow down your servos with pulse width modulation when flaps are up, or when GPS is going fast (if you program it to read an external GPS NMEA sentence) or whatever.

The possibilities are endless, the code is really easy, and once mounted in a nice aluminum housing with good quality components and D-sub connectors, it becomes super easy to mount and wire.

Anyway, I'm going to build myself at least one and a spare and wanted to know if anyone else would be interested in a arduino compatible board that was ready to mount and wire.





Feedback is welcome, as I know there are some EE types floating around here.

Last edited by akschu : 02-14-2018 at 01:59 AM.
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  #2  
Old 02-14-2018, 05:28 AM
BBaxR6 BBaxR6 is offline
 
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That sounds pretty slick, I'll be subscribing to this thread to see what comes about! I've been rolling a similar idea around after watching a YouTube video about motor drivers and PLCs. But then I start to wonder if I'll ever actually finish an airplane if I keep concocting all these little side engineering projects
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  #3  
Old 02-14-2018, 09:04 AM
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vlittle vlittle is offline
 
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Hi Matt, nice going. It is nice to see several folks using Arduino stuff in the cockpit. For reference, here is my thread on Arduino:

http://www.vansairforce.com/communit...hlight=Arduino

Here are the documentation links:
http://www.vx-aviation.com/documents/Falcon-AVR/
http://www.vx-aviation.com/documents/Talon-AVR/

Go ahead and borrow anything you want from the design, or contact me via PM. I am using this device to run the autotrim and autoflaps in my Rocket.

There are other VAF threads on Arduino that provide useful information.

Have fun with this, Vern
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Old 02-14-2018, 10:41 AM
ssokol ssokol is offline
 
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Default Power supply suggestion

Love the idea, but one suggestion: that TI TLV1117 is only rated for up to 16v input. You might want to find a different switcher that can handle 28v continuous input and something in the 60v range for maximum input voltage.

The 60v max isn't absolutely necessary, but it protects you from most of the potential gotchas and it's the voltage the FAA uses as the "must survive" level for many tests.

Any chance you could toss an ESP32 on there for Wifi connectivity?
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  #5  
Old 02-14-2018, 01:52 PM
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jdeas jdeas is offline
 
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Default Search automotive power supply examples

Quote:
Originally Posted by ssokol View Post
Love the idea, but one suggestion: that TI TLV1117 is only rated for up to 16v input. You might want to find a different switcher that can handle 28v continuous input and something in the 60v range for maximum input voltage
Also consider a diode for the power in. Many regulators react badly to a hard negative voltage spike.

Can share some some of these from my own CANbus trim controllers by PM if you like
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Old 02-14-2018, 02:03 PM
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DaleB DaleB is online now
 
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Easy to swap in a pin-compatible regulator with a better max supply rating. I'd suggest a series diode on the supply input to protect against reversed power; you have no idea how many people managed to smoke a couple of my products before I started doing that. Just a thought.
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  #7  
Old 02-14-2018, 04:06 PM
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akschu akschu is offline
 
Join Date: May 2008
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Quote:
Originally Posted by vlittle View Post
Hi Matt, nice going. It is nice to see several folks using Arduino stuff in the cockpit. For reference, here is my thread on Arduino:

http://www.vansairforce.com/communit...hlight=Arduino

Here are the documentation links:
http://www.vx-aviation.com/documents/Falcon-AVR/
http://www.vx-aviation.com/documents/Talon-AVR/

Go ahead and borrow anything you want from the design, or contact me via PM. I am using this device to run the autotrim and autoflaps in my Rocket.

There are other VAF threads on Arduino that provide useful information.

Have fun with this, Vern
Vern,
Thank you for the information. I didn't realize that you had already done this. Great minds think alike eh?

I would probably just use your solution, but it lacks a digital pot, so I don't think I can sample the servo position AND feed it to the EFIS at the same time, which is important to me since I'm going to sync the servos.

I looked at the makerplane website but didn't see a falcon available for sale. Are you producing those?

Thanks,
schu
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  #8  
Old 02-14-2018, 04:16 PM
akschu's Avatar
akschu akschu is offline
 
Join Date: May 2008
Location: Houston, Alaska
Posts: 222
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Quote:
Originally Posted by ssokol View Post
Love the idea, but one suggestion: that TI TLV1117 is only rated for up to 16v input. You might want to find a different switcher that can handle 28v continuous input and something in the 60v range for maximum input voltage.

The 60v max isn't absolutely necessary, but it protects you from most of the potential gotchas and it's the voltage the FAA uses as the "must survive" level for many tests.

Any chance you could toss an ESP32 on there for Wifi connectivity?
Great catch, I'll swap out the regulator.

As for the ESP32, Its it's own microcontroller so I don't see why you would want a atmega and an ESP32 at the same time.

I looked at just swapping the atmega for the ESP32, but the packaging is a bit more challenging to solder, so if I do that, I would probably just make female socket so that you just plug in an ESP32 breakout board, like the sparkfun board.

Even then, the development environment around it isn't nearly as mature. So for your sudo-geek (not uber-geek) it would probably be pretty challenging to get going, while the atmega works perfectly with the arduino IDE.

What would you use the bluetooth or wifi for?

Thanks,
schu
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  #9  
Old 02-14-2018, 04:17 PM
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akschu akschu is offline
 
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Quote:
Originally Posted by jdeas View Post
Also consider a diode for the power in. Many regulators react badly to a hard negative voltage spike.

Can share some some of these from my own CANbus trim controllers by PM if you like
Good catch, I'll add one.

schu
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  #10  
Old 02-14-2018, 04:42 PM
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vlittle vlittle is offline
 
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Quote:
Originally Posted by akschu View Post
Vern,
Thank you for the information. I didn't realize that you had already done this. Great minds think alike eh?

I would probably just use your solution, but it lacks a digital pot, so I don't think I can sample the servo position AND feed it to the EFIS at the same time, which is important to me since I'm going to sync the servos.

I looked at the makerplane website but didn't see a falcon available for sale. Are you producing those?

Thanks,
schu
All I have is a few blank pcbs.
V
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