Proper grounding, powering and signal protection of Arduinos in a vehicle

Noob alert!

I'm tinkering on my garage project, standard vehicle stuff - 12V lead acid battery, 3-phase stator, reg/rec. I would like to put few additions to its circuit. Being a rookie, I'm not sure how to approach this correctly in terms of providing safe 5V for the Arduinos (I need few of them). I've read a lot of articles on transients and noises in vehicle environment - load dumps, over and undervoltages, spikes...and also proper grounding, ground loops, it just seems overwhelming -
hence this thread.

I've sketched up (sorry for any drawing mistakes) the circuit I plan to make, there's two of the sketches actually - the difference being grounding of the Arduinos, since I don't know which method is actually correct, grounding them to chassis or grounding them to the buck converter that will be providing the 5V. I have a Traco Power TMDC 20 unit for this job - if you have the time you can look up its specs, from my limited knowledge that converter should be good for my use case but do let me know if its not.

Also another issue I'm worried about is grounding Arduino's buttons for logic level signals - I presume they all should be grounded on the Arduino GND pin - but then there's a issue of physical distance. The buttons themselves will be at least 2 meters away from the Arduino, if not more - so this makes me think about interferences, noises on the wire, etc - how do I approach that issue? Here's the schematic and thanks for any help :pray:

Here's a direct link to the image for higher res -

Why would you use more than one Arduino? :astonished:

Ah thanks for your advice. Why more than one Arduino, why even do this...very metaphysical stuff. Thanks, very helpful.

Wow. That should work. I only say becaus when I see ppl using these, the cheap ones, I have some advice. Your choice, at many times the cost, seems to have no issues that I can comment on.

As for multiple Arduinos (Arduinae?) we tend to find that noobs will throw another Arduino on into there rather than take the time and trouble to get one sketch doing all everything, which in 99.44 % of cases is totally within the capabilities of one board.

But you do you. There are plenty of defensible reasons for using multiple processors, even just saving time is valid. In the automotive environment, which you know to be a tough place, it may make some things easier.

Have you considered using an automotive comms bus for this project? I ask because if so, and you aren't opposed to dropping Arduinos in there like so much pepper, you could do the buttons, for example, with an Arduino right there, then send that to the one a few meters away, benefiting from the works-by-design characteristics of the hardware and software protocol.

That might offend even more people. I'd do it and still be able to look at myself in the mirror. :expressionless:



I have found these units to be extremely reliable in industrial and earthmoving control applications.

Sorry I don't get it. (I'm not into Heavy Metal) :laughing:
I looks like you are using an Arduino for just a few tasks, is there a reason why one Arduino controller cannot do it all?
Do you need to have these many Arduino talk to each other?
What model Arduino are you using.
Do you have your project breadboarded and working?

Don't forget a 12V system, is actually 12.5V and can go up to 14.4V in some vehicles during charge.
Will you be putting a fuse in the input to the DC-DC converter?

We need a bit more info to give you any reasonable info, just for power configurations.
Is any of the wiring going into the engine compartment.
Is the engine electric, petrol (gas) or diesel?
What are the 5V sensors.

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

This is the part that confuses me to no end. I've asked this question on another forum, and the Traco Power was described as unfit for my use case because I can't handle over 50V - which might happen during some spikes in the vehicle circuitry. Baffling :smiley:

Why multiple Arduinos? That's a good question. One Arduino is solely for high side switch so I wouldn't want to put anything else in that sketch because it's pretty crucial. Second Arduino is there for that reason - I'm aware it's a quack solution, but those 2 Nanos could fit in an enclosure and nobody will know :smiley:

As for comms bus - I don't have it in my case. So I'm left with regular wire to run the logic signals, and this is again where forum noise comes in play - some people say 2 or 3 meters is a non issue, others say I should use shielded wire so...I guess the only way I'll know is to experiment by myself.

@TomGeorge I replied to the other member about this - one Arduino (Uno) has to be there to use the high side switch shield, so since it's crucial business I'd rather not add any other code to loop there - I figured one Nano isn't expensive and can control that one sensor like a dedicated unit. That's really not big of a concern, Nano's small - but I'm worried more about safely powering those 5V devices and how to make sure that the signals from digital pins travel 3meters of distance safely without interrupts or noise.

Yes, but google (Google) is your friend, you are hardly the first person out there…

Perhaps you could look at the physical layer of an automotive bus to see how they work it, exploit that w/o necessarily buying into a full up comms bus.

Like twisted pairs and current loops and and and shielding and and and.

Also, if you have switches or buttons, you should may have to do more than normally required to debounce them. On a blender, a pushbutton won’t capricious close or open on its own. In the automotive environment you may still have glitches in either state that must be software filtered.


On my sketch I do use EZbutton library, and internal pullup of course, not sure if that's enough. As for the wiring - I'm reading on shielded wires, and find more confusion :smiley: some say "ground the shielded wire on one side only", others say both sides....

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