Help before buying sensors for Arduino Uno

Using Arduino Sensors
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Dear all,
I am a newbie and I have been asked to figure out if it is possible to interface a set of three humidity/dewpoint sensors with an Arduino Uno board.

The sensors I have to test are:
CSInstruments FA 510/515
PST Michell Easidew EA2
Vaisala DMP7

My understanding is that all of these sensors require some tweaking to be interfaced with Arduino, both in terms of coding and in terms of hardware connections.
For example, all their datasheets mention Modbus-RTU over RS485 communication protocols, and MiniDIN 43650 form C or M12 5 Pin (A coded) connectors.
I have been looking online and in this forum (topics such as this and this) but I could only find bits of information that, due to my extremely limited knowledge, I am not able to put together to figure out if they could work with Arduino Uno.

So, to recap, my main questions are:

  • Is it possible at all to connect these sensors to an Arduino Uno board and with which kind of adapters (for example to the M12 connectors / RS485 communication, are there any)?
  • Is it possible to write Arduino code that interfaces these sensors with the board, and are there available libraries that do so, or resources online that I might have missed? I could successfully connect sensors such as the HYT939 using a I2C protocol and the ad-hoc adapter and libraries (wire.h etc), but I was only able to do it thanks to various examples I found online. I doubt I would be able to write something from scratch with more complicated hardware.

Any help is really appreciated :slight_smile:

2

I can't address the physical connector but there's this:

The first two also mention 4-20 ma current loop.

3

it sounds like you get paid to do this. you are certainly not spending your own money here.

break your problem down into search terms:

arduino current loop library - and you find 4-20 ma current loop module

you need a datasheet on that EASI-DEW

the DMP7 requires 15 - 30 volts. that would put it on the bottom of my pile.

I would pass on the UNO and go straight to a MEGA, or bypass that and go to an ESP32. the what you get for what you pay ratio favors the ESP32 by a long ways

4

Thank you both for the answers,

dougp:
I can't address the physical connector but there's this:

ArduinoModbus - Arduino Reference

The first two also mention 4-20 ma current loop.

Thank you, this was very helpful and I am looking into it.

[quote author=Geek Emeritus date=1617848799 link=msg=4953154]
it sounds like you get paid to do this. you are certainly not spending your own money here.

break your problem down into search terms:

arduino current loop library - and you find 4-20 ma current loop module

you need a datasheet on that EASI-DEW

the DMP7 requires 15 - 30 volts. that would put it on the bottom of my pile.

I would pass on the UNO and go straight to a MEGA, or bypass that and go to an ESP32. the what you get for what you pay ratio favors the ESP32 by a long ways[/quote]
I agree that breaking down the problem makes it easier, but I still can't figure out if M12 cables would work with Arduino UNO (and I am not allowed to change it to the ESP32 or the MEGA) so I guess that is the missing piece for me now.
P.S. - I have to buy the components with my own money to begin with, but I don't see how this is relevant to my question in any way : )

5

abschuby:
but I don't see how this is relevant to my question in any way : )

On this forum we like to know what the overall project is about for a broader view. Everything is relevant. When someone has a problem, then that person is often too much focused on a detail which could be the wrong problem in the first place. See https://xyproblem.info/.

Is it possible to connect RS-485 or a current loop of 4-20mA to an Arduino ? Yes.
Are there libraries for that ? Yes.
Do you need some knowledge about sensors, programming, electronics and dewpoint physics ? Also yes.

The 4-20mA is easier to connect to a analog input. You don't need a library. You can start with that to know that it is working. By the way, don't connect those wires directly to an Arduino board, you will instantly destroy the Arduino board.
With multiple sensors, I prefer the RS-485.

A Arduino MKR board with RS-485 shield is a good start. There are also RS-485 modules for the Arduino Uno.

6

The 4-20mA is easier to connect to a analog input. You don't need a library. You can start with that to know that it is working. By the way, don't connect those wires directly to an Arduino board, you will instantly destroy the Arduino board.
With multiple sensors, I prefer the RS-485.

A Arduino MKR board with RS-485 shield is a good start. There are also RS-485 modules for the Arduino Uno.

Thanks for this, it's very useful.
P.S. - Gender, salary and ethnicity are not relevant to any Arduino post and it certainly does not take an Arduino expert to understand that. So let's avoid rude comments such "You are certainly not using your own money here" that in fact did not add anything to the topic, thank you :slight_smile:

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