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CAN nodes and Arduino operating temperature

chubsterini

Well Known Member
Hi,
I've been playing with Control Area Network using Arduino.
I was thinking about the possibility of placing a CAN node at different places on the airframe (e.g., behind the panel, at each wing, at the tail, etc) so that switches and and other components can plug into the closest CAN node and the function be defined via software. I'm mainly thinking of controlling the lights and pitot heat, and perhaps also add some remote sensors etc. This should make wiring a lot simpler and future-proofed against upgrades and such.
But then I learned that Arduino's recommended operating temperature range is -25C to +70C, the low end of which can be busted on a cold day at reasonable altitudes (the controllers behind the panel will probably be fine, but I'm worried about the ones in the wings and tail).
Has anyone done anything similar, and how was this addressed?
I guess it's possible to heat the controllers by adding a thermistor or some such... but then things start to get more complicated.
My project is still in the early stages. So this is mere idle fancy at the moment.

Thanks
-c
 
Is Additional Circuitry Really Cumbersome?

Charlie,

A few of random thoughts.

What about venting air from the cabin to each remote CAN node?

Why not leave the CAN nodes strategically inside the cabin such that only the bus and power get pulled throughout the airframe (the'll have to be anyway) and the device wire gets pulled from that point out? This remains consistent with the spirit and intent of your stated purpose, I think.

Lastly, a thermistor is used for temperature measurement. It's not going to keep a board warm (am I missing something here?). Adding a small piece of heat strip controlled by a relay and monitoring ambient with a thermistor / thermocouple / RTD don't dramatically increase complexity.

I often wonder why this application has not already been done.

What is the appeal of CANbus?

Mike
 
Thanks for your thoughts, Mike

What about venting air from the cabin to each remote CAN node?
Seems complicated. Also how much cabin air is required will vary by condition.

Why not leave the CAN nodes strategically inside the cabin such that only the bus and power get pulled throughout the airframe (the'll have to be anyway) and the device wire gets pulled from that point out? This remains consistent with the spirit and intent of your stated purpose, I think.
any device connecting to the bus would be a node and would need to know how to behave like one (so in my case that is done using arduino), which is why the arduinos are not all inside the cabin.

Lastly, a thermistor is used for temperature measurement. It's not going to keep a board warm (am I missing something here?). Adding a small piece of heat strip controlled by a relay and monitoring ambient with a thermistor / thermocouple / RTD don't dramatically increase complexity.

Yes... but I guess then I'm thinking I should enclose the electronics so as to encapsulate the heat, and maybe monitor the temperature as opposed to just relying on the thermistor to auto-regulate the temp... I.e. more complexity.

I often wonder why this application has not already been done.

I had assumed it's been done and is well-worn, which is why I posed the question. Still hoping some experienced builder will clue me in or definitively shoot the idea down.

What is the appeal of CANbus?

Mike

I'm sure there are lots of other ways to accomplish the same thing, but I figure CAN Bus paradigm is well tested and reliable. Operating temperature aside, Arduino and the various available CAN shields make this cheap and simple to implement.

The Ruggeduino's claim of -40C doesn't give me all that much comfort over the normally recommended -25C. But perhaps there are other microcontrollers that are more cold-tolerant?

I'll finish with some possible use-cases:
- adding a simple current sensor at the remote device can provide positive feedback via an indicator inside the cockpit that the device did turn on and is drawing current, e.g., for lights and pitot heat, etc.
- wigwag any combination of lights without any additional components (I.e., the individual lights can coordinate each other: "wag when I wig").
- have a dial on the panel that chooses phase of flight (taxi, takeoff, climbout, cruise, etc) and, in conjunction with a light sensor and cached sunrise/sunset tables, have all the FAA lighting requirements encoded in the controller and lights automatically switched on/off.

None of this is groundbreaking. And, given there are only a few things one would want to put in a wing or tail, future-proofing might not even be justified if this solution is itself complex (which is why I'm balking at the thought of routing cabin air or adding heating elements).

I just thought this would be fun.
 
We are working on the wings at this point, so the following is based on observations here on VAF by others, not actual experience.

Yes, but why locate the nodes at extremities?

One motivation for building this application is to minimize wire runs fore and aft. My understanding is that routing is an art and is a huge challenge. So, if we go with the network concept placing these remote nodes strategically within the cabin, this challenge is significantly reduced to power and network.

What is the benefit of locating a CAN node outside of the cabin? If we can reduce the fore / aft wire run problem to power and network, wire installation from the nodes to end devices is much easier. Wire is heavy, but there is not much on an RV (relative concept, flame throwers!). Locate CAN nodes within the cabin and pull device wire from each node to the end devices. The temperature problem goes away entirely. BUT, if one of your goals is to minimize wire runs to end devices, this paragraph becomes moot.

I like the concept and do lots of this kind of work in my day job albeit not at the board level.

One man's opinion disclaimers here....

Agreed, the project would be fun.

Best regards,
Mike
 
Yes, but why locate the nodes at extremities?

One motivation for building this application is to minimize wire runs fore and aft. My understanding is that routing is an art and is a huge challenge. So, if we go with the network concept placing these remote nodes strategically within the cabin, this challenge is significantly reduced to power and network.

What is the benefit of locating a CAN node outside of the cabin? If we can reduce the fore / aft wire run problem to power and network, wire installation from the nodes to end devices is much easier.

Thanks Mike, for your support and suggestions. You may be right that locating the controllers inside (eg near the wing root) could work, and for sure it simplifies wiring when compared to connecting devices directly to switches at the panel.
But in my example (an indicator of the device drawing current) it would require fishing additional wires through the wing from each device. Perhaps this is still better than trying to climate-control the arduino inside the wing.
I’m still hopeful there are more simple solutions.
I have time to mull this over before I’m at the point of wiring. In the meantime I’m grateful for any and all suggestions.
Thanks again.
 
Additional Wiring for Current Draw

Charlie,

A simple CT for each device, while they can be relatively heavy, can be co-located with the controller and require almost no additional wire. You can mount them at any location where the load circuit is run.

My curiosity is related to getting aft of the main spar in a -10.

FYI,
Mike
 
Time for the wet blanket to step in again...
* What are the failure modes?
* How do you handle inflight failures?
* How do you document your system and software so that two years after installation, you can fix something that you didn't think about originally?
* What's the user interface going to be, so that you can spend full time flying the airplane and not fussing with electronics, especially on first flights?
* When time comes to sell the airplane, then what?

Van once told the story of somebody who spent all his effort getting a beautiful shop together, and when he was done, realized that his objective was having a great shop, not building an airplane. Similarly, ask yourself the hard question - fly an airplane, build an airplane, or build electronics?

Personally, I think it's a great concept to talk about, but I have serious reservations as to the risk/reward for an airplane installation. A homebuilt already has enough things to stay on top of...

Be well!

Ed
 
My initial "wet blanket" thought was about where do the fuses and circuit breakers go?
Simple can be best!
 
Time for the wet blanket to step in again...
* What are the failure modes?
* How do you handle inflight failures?
* How do you document your system and software so that two years after installation, you can fix something that you didn't think about originally?
* What's the user interface going to be, so that you can spend full time flying the airplane and not fussing with electronics, especially on first flights?
CAN bus and microcontrollers aren't inherently more failure prone, and given the wiring is significantly simplified one might argue the end result is more stable and robust. But of course that depends on the implementation (which is why I am worried about operating limits with regard to temp).
Documentation is the same amount of work regardless, but admittedly it would require the reader to understand CANbus and microcontrollers.
User interface will be the same if not simpler.

* When time comes to sell the airplane, then what?
Only someone who is fond of electronics would see the implementation as a value add. It's sure to be a negative selling point for everyone else.
But as I'm building the plane for myself I'm not particularly concerned about selling it down the road. This isn't economically prudent.

Van once told the story of somebody who spent all his effort getting a beautiful shop together, and when he was done, realized that his objective was having a great shop, not building an airplane. Similarly, ask yourself the hard question - fly an airplane, build an airplane, or build electronics?
Touché! That describes me to a T. I like to build and make things. Flying is secondary. I would have assumed I'm not unique on this forum, since if flying is the goal above all else we'd just buy a plane and forgo the building altogether.

Personally, I think it's a great concept to talk about, but I have serious reservations as to the risk/reward for an airplane installation. A homebuilt already has enough things to stay on top of...

Be well!

Ed
It's only worth doing if this simplifies the build, reduces maintenance complexity, and reduces operating workload. That's my goal anyway (aside from the cool factor). But I'd be the first to admit that these factors are relative to the background and skillset of the builder/operator. I'm much better with programming and MCU's than I am at pulling wires etc.


My initial "wet blanket" thought was about where do the fuses and circuit breakers go?
Simple can be best!

Fuses and breakers are with the power. This doesn't change that. Consider it just a more involved network of relays.
 
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