Arduino Sensor Connection and Data Export to a smart phone

So far, I got the system to control the temperature and monitors the pH of a water tank. The temperature/heating system works on one circuit with a built-in display. The pH system works on a sensor attached to a circuit which is connected to an Arduino ​Uno that is connected to an OLED display to show its output. I want to add a dissolved oxygen measuring meter as well but I would like to combine all these sensors' output to an Arduino in order to analyze it all from one source instead of having too many circuits everywhere.

​Is there a circuit with all these sensors attached, which connects to an Arduino from which I can output the data through bluetooth or cellular data to a smart phone?

Welcome lehansa! Probably not, but it would not be that hard for you do design it. It appears you have each sensor working with its own Arduino. If that is correct do you have the source code? If so you have about half of your problem solved. Check the schematics of the existing ones and if they each use different pins great, if not you will have to assign a different pin(s) to each sensor unless they are I2C, then they stay on the same two pins. You can output via bluetooth, I do not know about celular. Have fun with your project and let us know how you progress. When you ask additional questions post links to the technical side of the hardware devices.

I will leave others to talk about connecting the sensors to Arduino, but my (paid) pfodApp can handle the connection via bluetooth or SMS or WiFi or BLE to an Android mobile.
There is a free pfodDesigner Android app that will generate the Arduino code for you to make the connection and numerous example sketches.
This one does 3G/2G SMS

Welcome to the forum.

There are a few things we do not know. So, here are a few general points.

BLE is great when you need low power. e.g., when your sensor runs from a battery. The drawback is you need an app to interact with your BLE device. There are generic apps (BLE Scanner, nRF Connect, ...) that allow you to read and write raw data. But for a good user experience you need to write your own. Maybe the app from drmpf is something in between.

When you have power available you can use WiFi. It allows you to run a local WebServer that provides an interface that anyone can use. With some HTML and CSS knowledge you can make that very pretty.
You can have a secure WPA2 access point or connect to your home WiFi. There are additional options if you want to extend this system e.g., local or cloud data storage and analysis.

There are a couple of Nano sized Arduinos that have WiFi and/or BLE build in. Only you know how many I/Os you need. You can even switch between BLE and WiFi with some Arduinos.

Hello! Thanks for your reply,

The temperature sensor senses and displays the output on a built-in display but I need one temperature sensor that will connect to the arduino to be displayed on a phone, so I plan on using another sensor shown here:Add WiFi to Arduino UNO - Arduino Project Hub

The pH sensor is connected to an Arduino which is connected to an OLED display as shown in this website: https://how2electronics.com/ph-meter-using-ph-sensor-arduino-oled/

Also, gilshultz, (I had to cut the message in half because of the link and media limit)

I am planning to connect the dissolved oxygen sensor as shown here: https://how2electronics.com/dissolved-oxygen-sensor-arduino-interfacing-tutorial/#:~:text=The%20sensor%20works%20at%203.3,to%20A1%20of%20Arduino%20Board.

I checked some of the pins used for the oxygen and pH systems and found that both the OLED display and use a GND pin (also, I switched to a wifi module ( I plan on connecting it this way: Add WiFi to Arduino UNO - Arduino Project Hub) which uses a GND pin) but there are only 2 GND pins so I don’t know what to do). Also, the wifi module and another sensor both use the 3.3v pin and there might be more pins.
Should I get a breadboard or is there a different way to connect all of this?

(The schematics are included in the websites).

@Klaus_K

Thank you for the feedback: just to clarify, compared to BLE, wifi draws a lot more power, right? In other words, if I am using a battery which one would work better?

There is no better. It is a compromise between bandwidth and power. Maybe using BLE and WiFi would be the best solution for what you would like to achieve.

Can you describe the use case a bit more?

  • Is the device active all the time or once a day, hour ... ?
  • Is the radio active all the time or once a day, hour ...?
  • How much data do you need to transfer?
  • ...

The only thing you can say with certainty about the choice is that Bluetooth is more convenient. This goes double if you are already using a Uno, which is not such a great choice for working with WiFi. The rest is down to you, and any technical differences may be irrelevant anyway. I would use Bluetooth every time simply because I'm not aware of a WiFi terminal programme that is a direct equivalent to the Bluetooth terminal I use, and there has never been any motivation to look. This decision has nothing to do with Arduino.....

@Klaus_K ,

I expect all these aspects to be active for about an hour or two a day, and I expect I might need to transfer 1-2 MB, but I am not completely sure yet because this is the first time I am trying to transfer raw data.

Take a deep breath, you can connect all the grounds together. The UNO's I use have several ground pins, two together and one on the other side by Aref. You can connect all the grounds together, they are the same. If you have a small proto board you can use that to connect them. The ISP plug also has a ground.

The amount of data is low enough to use BLE. On the other side if you only need to enable WiFi once a day to send the data you can also use WiFi with a battery.

You can chose the protocol that you can use to create the best user experience. That depends on your skills. Do you want to use a BLE app or a web page?

That is a key point. Coding a BLE app is a pain where as you still display your webpage on your mobile.

If you decide to use WiFi instead of Bluetooth(either classic or BLE) the path of adding an esp8266 module to a UNO is not an optimal route.

You would do better to use an fully featured usb interfaced esp8266 development board like the Wemos or NodeMCU.

For more IO and bluetooth integrated as well as WiFi, you should look at the ESP32 development board.