Which Arduino board to use?

Hi there,

I'm a beginner in Arduino, usually I'm the one writing the code behind my applications and buy things ready to go, but since I want to expand my knowledge here I am.
I've been searching all day right and left all across the internet for answers and I've found... well way too many actually.

Here's my problem and what I want to achieve personally:
I'll be getting two 4-20mA input signals and one or two digital inputs, upon which I will generate a signal (also analog, 0-10Vdc) for my appliance to respond. It's output will be one (I'd like to have two, but see further on), and one to two DI to close a relay.
The board will calculate it's output based on the values of the two inputs returned by the transmitters.

So far I've narrowed it down to these options:

Arduino Nano Every:

  • Can read analog signals
  • Can't output them, but apparently it's solvable with a DAC and something called an OpAmp. I've read this and somewhat understand the principle, but more explanation is always welcome if you feel like it.
  • Works on 5V which makes it easier for me to find the right OpAmp, atleast if I'm understanding the principle of an OpAmp correctly.

Arduino Nano 33 IoT:

  • Can read AI
  • Has one AO, atleast I think it does. If I'm correct I can double this with an OpAmp?
  • Works on 3.3V and I don't know if this is boostable by the OpAmp?

I've found several more Arduino boards in the store which have a DAC output but those are a bit more expensive and I think I have plenty of what I need in those two boards, unless I'm mistaken?

I'm also still confused about some basic things and I do feel really dumb for asking them but here goes:

  • Both transmitters operate on 24Vdc (I will use a seperate supply for them I guess) but will their return values break the board? Because either I'm dumb or I'm only getting ~1V return from them. Yes I do understand Ohms law but I rather be safe than sorry.
  • ... I had a ton of questions researching this and I seem to have forgotten them now that I'm asking. Great, I guess they'll come when I have some more clarity.

Thanks in advance!

You will probably get better answers if you provide a brief overview of what you're trying to do.

wildbill:
You will probably get better answers if you provide a brief overview of what you're trying to do.

Uh, okay.
Two hygrostat transmitters (for measuring relative humidity) provide me the data. One of those inside the extracted air, another one close after the distributionpoint. The latter one will act as a 'high limit' transmitter, warning me when the air inside the duct is becoming close to saturated.

The return value will let me calculate how much I need to pump in whilst the highlimit will be factored in so it won't oversaturate. Both are 4-20mA as said. But my appliance only responds to 0-10Vdc.

Further the other two DI are for checking there isnt an error in either appliance (in which there'll be no more signal, consider this a cutout) and the DO will be for passing on the error to the appliance and/or pointing out the arduino has an error.

A little outside my league but to my knowledge
1)
4-20 mA needs to be translated at the Arduino side to a voltage; 20 mA could e.g. translate to 5 V in which case 4 mA to 1 V; to my knowledge you just need a resistor (5V/20mA = 250 Ohm, adjust for 3.3V).
2)
0 mA would translate to 0 V, allowing you to detect a broken wire.

Based on that, an analogue input would be more suitable.

Why do you look at the Every? Would a normal Nano not be as suitable?

Can not comment on opamps.

sterretje:
A little outside my league but to my knowledge
1)
4-20 mA needs to be translated at the Arduino side to a voltage; 20 mA could e.g. translate to 5 V in which case 4 mA to 1 V; to my knowledge you just need a resistor (5V/20mA = 250 Ohm, adjust for 3.3V).
2)
0 mA would translate to 0 V, allowing you to detect a broken wire.

Based on that, an analogue input would be more suitable.

Why do you look at the Every? Would a normal Nano not be as suitable?

Can not comment on opamps.

You.. you're right. How did I miss this? I think I started at the Every for the price range and never got beyond the 33 IoT or something..

Okay so we can assume I'll be going for a regular Nano then.
I was already planning it like how you're responding, which is awesome by the way thanks for reminding me!

For the remainder of the questions;

  • Will the output of the transmitter break the board?

EDIT: Isn't the Micro equally capable?

leandromarceddu:
For the remainder of the questions;

  • Will the output of the transmitter break the board?

EDIT: Isn't the Micro equally capable?

The 24V will not reach the Arduino, the voltage on the Arduino depends on the resistor that you use.

I would say that the Micro is more capable as its processor supports USB. As I haven't looked at prices, I can not say what is the better choice.

What bandwidth and resolution do you require for the 0-10V DAC?

aarg:
What bandwidth and resolution do you require for the 0-10V DAC?

As resolution 100 would be ideal, but seeing that's not achievable due to an OpAmp basically doubling your voltage; 50 is fine.

Unsure about what you mean by bandwidth?

leandromarceddu:
As resolution 100 would be ideal, but seeing that's not achievable due to an OpAmp basically doubling your voltage; 50 is fine.

Unsure about what you mean by bandwidth?

What do you mean about the op amp doubling your voltage? I've never had that problem - op amp gain is specifically adjustable by design and almost any gain is achievable. They often have S/N of 85-90dB which translates to roughly 14-16 bit resolution. Lots of 24 bit D/A's use op amps too. Do you know what D/A resolution is generally? It sounds like not. It's like, how many output voltage steps (where each step corresponds to each digital input quantity).

Bandwidth means, how fast do you need the output to change.

aarg:
What do you mean about the op amp doubling your voltage? I’ve never had that problem - op amp gain is specifically adjustable by design and almost any gain is achievable. They often have S/N of 85-90dB which translates to roughly 14-16 bit resolution. Lots of 24 bit D/A’s use op amps too. Do you know what D/A resolution is generally? It sounds like not. It’s like, how many output voltage steps (where each step corresponds to each digital input quantity).

Bandwidth means, how fast do you need the output to change.

Right, I didn’t know that an OpAmp is adjustable in output. I basically thought it’d just take whats given and doubles it. Seeing as it’s adjustable, 100 would be neat. That way 0-10V represents 0-100%, for ex 5V would mean 50% and 6,3V 63%. As I said I’m not entirely sure about what things like op amps do; I’m usually on the software side of this and on that side you got a broad set of datasheets about what things can and cannot do.

How fast? Not that fast. Heck I’d say once a second is plenty.