I barely have an idea what an Arduino is, and have no idea what is an Arduino shield. But I admire such unequivocal responses!
I also read about that: https://support.arduino.cc/hc/en-us/articles/360018922239-What-is-the-AREF-pin-for-
But what use do I have of that.
I don’t want to over comlicate any thing.
The thing is, how to connect a pot on arduino. On pokeys it is quiet clear to me, and have worked for 10 years in my simulator.
I would need too much background study to understand most of this discussion. I do not know what are “pokeys” but the answer to that question would probably lead me to another question.
However, in simple terms you can theoretically power a load (such as 5V @ 2 Amps) from one of several input sources by using “ORing diodes”.to automatically select the highest voltage source. The issue with that is the diodes will waste 300 mV to 700 mV (sort of a typical range) depending on whether you use schottky or general purpose silicon diodes. This voltage drop can be virtually eliminated with any one of several “ideal diode” circuits. A discrete version of this uses op amps and MOSFETs. If a higher bias voltage (such as 12V) is available it can use Nch MOSFETs. If the bias voltage is not available, then the design can use “low threshold voltage” Pch MOSFETs.
I don’t really understand what this have to do with connecting a potentiometer to arduino?
The important thing as I understand it is to not mix input voltage with output voltage from Arduino?
What handful of considerations?
I thought this questions was quiet simple and could give a simpler answer? Every thing seems more comlex.
I cautioned against it (word “Should” not). Did not say “Must” not.
Why did I say this (you asked)?
Because (to me) you seem too unfamiliar with this stuff and, thus may not realize aspects of power dithering and drop-out. It’s like “Chewing Gum” I know it’s not good to swallow, though it won’t kill you but, I’d avoid recommending it. What if you changed power supply to a 7v source (because you know it should be okay, per spec) and it hovered around 6.7v and you’re attached (heavy-load) devices pulled it down even further?
Your question about hooking up a Pot is the simplest/basic thing to understand yet, you seem too unfamiliar with it. Arduino, Pokey, ESP, PIC’s… long list but, the hook-up is the same. It’s First-Grade electronics.
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It is related to:
“how to Power” (I cannot automatically quote from the title of this thread)
and
I do not understand so much of the discussion. But if you have several sources, you may be able to power from the most robust input source.
I was trying to nudge this topic off site since it isn’t really Kicad related. I was hoping it would stay short.
I think that your heart (and probably also your other organs) are in the right place. Please feel free to IM me in blunt terms when you deem appropriate.
Well guys I got answer from Pokeys:
This is what they said, cant be more clear than this:
Analog inputs of PoKeys devices can accept voltages between 0 and 3.3 V as described in the user manual. You should not connect more than 3.3 V to any of the analog input pins - higher voltage will irreversibly damage the device. We suggest you use 3.3 V power supply output available on one of the PoKeys pins to power the potentiometer.
This means jumper if I want to use 5 volts for arduino and 3.3V on Pokeys.
I have to seperate input power and signal power.
But the question remain. Wher should I take power from to pot if I connect arduino?
My thought is 5 volt from ardino out, and input power 5 or 12 volt should not be connected to signal power.
I have done wrong and will corect it.
Thanks for the help.
One or two weeks ago I had a short peek at some data from the pokeys, and there does not seem to be any sort of attenuation or input protection on the pins, which is understandable, as the pins of both that arduino thing and the pokeys can either be analog inputs or digital inputs or outputs. You should not even attach long wires to such unprotected pins.
Why should I not do that?
Because they are too vulnerable.
IC pins are quite easily damaged by by all sorts of small accidents, from over voltage from for example faulty wiring, to even just by touching it. Even though IC pins usually have some ESD protection it is a fairly limited protection and definitely not enough when you’re wearing a woolen sweater on a dry winter day.
As long as signals stay on a single PCB chance of accidents is small, but as soon as you start adding connectors and wires to somewhere else it’s time to start adding some extra protection.
But what has that to do with long wiers?
Because those bords hole purpose is to connect inputs and outputs to flightsimulator or cnc.
How would you do that if not with wiers?
If I for example connect a switch to ground and a digital input, with 4 meter kabel. Ho would that be harmful in any way? Even if I Short the cabel to ground. I can’t see that long cabel would cause any problems with induction.
So I don’t see any problem wit 1 meter cabel or 5 meter cabel. The signal will come threw.
Oh boy 
You obviously have no clue about electronic connections.
An answer like this would have bin more helpful:
The length of the cable will depend on the type of signal transmitted such as whether it is analogue or digital, its frequency, low/high impedance of the signal source, the type of cable used and so on. For I²C, the length is better to be within 3 meters. The length can be made as long as 300 meters.
With a 22AWG cable length of 50 meters and a 100mA current, the voltage drop would be around 1 V. The capacitance of any cable will affect the rise and fall times of the signals. That can affect the measured duration of the pulse received from the sensor. As for the analogue signals, it may be important to add a capacitor to decouple the power to the sensor at its terminals. But, really I wouldn’t add capacitor alone to the sensor line. I will also add a resistor before the filter capacitor. In the case of an SPST switch, following this way you can practically use a 100 meter shielded cable (like CAT 5e cables or cables that are used for phone lines).
And back to the qusetion, will a digital input be affected by a 5 meter cable, most likely not.
Tell me a situation when a digital signal would have problems on a five meter cable? The probable length would certainly not be more than 2 meters.
I have received answers to my questions, thank you!
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I will feed Pokeys with external +5V DC just as I thought from the beginning.
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I will power the Arduino with external +12V DC.
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I will NOT mix input voltage with output from either Arduino or Pokeys.
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I will use a jumper to choose whether I should have Arduino +5V or Pokeys +3.3V for Potentiometer.
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I will not use external voltage to power the Potentiometer.
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I will use “VIN” pin 8 to supply 12V to the Arduino instead of via the connector on the card.
The only mistake I can see that I made and that I noticed myself, but wanted to get confirmed by you, was if you could, should mix external 5V and 5V from Arduino.
The answer was simple: No.
I have now redrawn and now it’s just details to get a good shield.
And my damn decision anxiety!
Should I have the hole there or there, should I settle for, should I make the card longer, is it enough to have D-sub without screws as attachment, how do I do this, this and this in KiCad.
On pretty much ANY arduino, you can and should bring in unregulated power, to the Vin pin and let the internal regulators (both 5 and 3.3v) do their own thing. You ca then power other boards off either the 3.3 or 5V - so long as they do not require more power than it can supply. read the specs and datasheet for your particular model. I would feed it at lest 7V. An alternative is to provide 5V and 3.3V external regulated power of your own design. from your questions it seems this is not an ideal solution. But it is how i make complex PCBs with an Arduino essentially embedded - i have my own 5V rail and attach to the arduinos 5V pin. On a nano for example, the maximum ground current (which equals the sum of all other currents) is, i thin, 200mA. On Mega its likely more. Aside from reading the rduino documentation it can be illuminating to read the chip’s datasheet (ATmaga blah blah blah i need coffee)
I gently hinted at the beginning, this thread isn’t really Kicad related and should be taken elsewhere. I hoped it would be short and die. I even mentioned that. But, it still is getting posts. We try to keep this site focused for various reasons.
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Then may be you can chip in on the kicad related issues in this thred: