Yeah that's for future reference. I want to get more idea before buying all the hardware. I'm still new with this electronic stuffs and it's little difficult to comprehend. I also have limited time on project, so any help would be great. Thank you.
Is it possible to get data from one sensor using RS485 Modbus, even if I dont have all six sensors at the moment?
Not with the current hardware you have. Remember, your sensor does not understand Modbus. It's serial port is really meant for a simple point to point serial link like RS232. You need the addition of an intelligent device line an UNO or similar to handle the RS485 addressing etc and the serial interface to the sensor.
I think that if you are just beginning with this, the introduction of Modbus adds a level of complexity that's not required.
Reading Nicks RS485 web page should give you a flavour of things.
RS485 by itself yes but the sensor does not use Modbus it has it own proprietary protocol.
It may not even work with RS485
As you have mentioned earlier, I need to use Pro mini and RS485 for each sensor to work with Modbus, right?
No. You can use a bunch of MEGA250 boards if you like. The Pro Mini is a nice small board which is why I first suggested it.
However, I wonder if initially you should use some MEGA2560 boards as you will need to debug your code with a lot of Serial print statements. That will use up the port called Serial. You will then have Serial1 to listen for RS485 messages and Serial2 to interact with your sensor.
Like here I have sensor that communication TTL serial, could you suggest a simple sketch to connect one sensor in a Modbus protocol?
I was referring to the following link:
Ok, then I need to learn more about RS485 communications.
Your sensor does not use the modbus protocol and not sure if RS485 will even work.
Even if I convert TTL to RS232 then another converter for RS485; I'm just curious to know if this works!
Just to muddy the waters slightly for you, there are 2 flavours of RS485. There's half duplex RS485 - where the same twisted pair is used to transfer data in both directions. And there is full duplex RS485.
This is an example of how half duplex RS485 is wired:
This is an example of how full duplex is wired:
Half duplex is what is mostly discussed here in the forum as most projects use a MAX485 chip.
The point to note is that you need some form of intelligent device to control the signals marked as /RE and DE to control the direction of flow of data.
Why?
Why do you want to use RS485? What is your reasoning?
You can certainly try it and see.
Exactly.
Fyi, modbus is a protocol and it's not related to RS485 even if often used together.
RS485 is a standard and you don't need to use modbus protocol with that.
If your sensor doesn't use modbus protocol, then you don't use it. Simple.
You started this project on the premise that this pyrometer would work with RS485 so you could monitor several sensors but as you are now aware, to do that will involve much more hardware and software.
So what do you want to do now?
After discussing with my supervisor, he said that this pyrometer has a analog output signal in mA and there is an additional converter which to connect PC for communication. Here are some images of the pyrometer:
Following image is the pin configuration of the Pyrometer:
Could you please explain the working of this pyrometer and the output function (Is this Analog voltage / Ampere OR digital)?
Got it. Thank you for the clarification.
I will try to connect the sensor directly to MEGA2560 and try to read data. If this doesn't work, I'll change the controller maybe try PLC!
If it does not work then you did something wrong and using a PLC won't make a difference.
Do you know what pins are what on the 15 pin connector you show?
Actually, I'm not the one who connected this. I'll ask the electronic department and get back to you. Do you have any take on Output signal of this pyrometer.
CSmicro LT-Manual.pdf (1.6 MB)
