Thank you for taking the time to read this post, I would love to know your thoughts on my study project
I am supposed to carry out measurements on volatile organic compounds. It's also part of my degree programme.
The measurements are to take place in a climate chamber. Two measurements at the same time. My biggest problem is the cable length. I want to achieve reliable measurements. Unfortunately, no Bluetooth or Wifi connections are possible in the climate chamber, as they shield too much.
So the cables would be fed through an outlet. I thought that both measuring points would be brought together at one point. I then received the requirement that the measured values should be accessible remotely. In other words, I should be able to access the measured values in the laboratory from the office. But here, too, I was given a lot of freedom.
Now I would like to hear your thoughts on feasibility. Which microcontrollers or Raspberrys should I use?
What problems might I encounter?
I have already started the first measurements outside the climate chamber. So the basics are in place
I am grateful for any input
I would like to see the current measured values of my sensors at all times. They will take a measurement every few seconds. During these 6 hours, I won't be standing next to them doing other tasks. I would like to track the success of my measurements in between.
may be you can just have the sensors within the climate chamber and have the µController outside the chamber. if WiFi is available there, then you don't need a "data aggregator", just have the µController (like an ESP32) use the WiFi network and IoT techniques like MQTT to send the measures to a central database (your RPi or some cloud stuff).
You could re-purpose some home automation software. I've used Domoticz in the past to log temperature and battery voltages from several wireless nodes. Each node was running a simple bit of code that I created that regularly sent readings to a gateway node which translated the messages into the MySensors format - in this case, using their simple serial protocol.
The MySensors network supports RS485 between nodes and the gateway device, which you could use as a way of communication from the chamber to the outside world.
Domoticz will store the data and will also graph it for you in real time. The wiki also says that the data can be exported as csv files for viewing in a spreadsheet.
@reallynotonsteam
For the microcontroller inside the chamber I would use an UNO R3 or a Nano.
For communications, I would use RS232.
For the main processor I would use a Mega2560 with the W5500 Ethernet shield, which also has an SD card slot.
That was also my first thought, but as I understand it, I can't use my SDA/SCL connection to the sensors over the entire length. The cables would be too long. I guess they would have to be 50-75cm each.
That was my thought too. I think I could set up an MQTT on the Ethernet shield.
if you go for 100 KHz for your I2C communication then you could have probably up to 1m of twisted pair wiring. You can also adjust the pull-ups. I think 50/75cm can be made to work.
just get an RPi somewhere on the same network, you can install Domoticz there too.
Oh yes but actually the server would be on the Mega2560
RS232 is probably the oldest communication standard around but you really don't need to know anything about it since in your code you would just use the standard Arduino Serial function to read and write.
This is very good to know! Do i have to take different RS232 Modules for the receiving and transmitting Arduino? Is there anything I should bear in mind when buying the cables?
This is how I imagined it:
Those modules are fine for both ends.
You will need a null modem cables sometimes called a cross over cable in order to connect the Uno to the Mega2560. Make sure it has Male connectors at BOTH ends.
The Mega 2560 has 4 serial ports
0(RX), 1(TX)
19(RX1), 18(TX1)
17(RX2), 16(TX2)
15(RX3), 14(TX3)
Use RX1/TX1 and RX2/TX2 for connections to the Unos.
